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Questions and Answers

What does the promoter region on DNA do?

  • It protects the mRNA from degradation.
  • It encodes the primary mRNA transcript.
  • It binds RNA polymerase and initiates transcription. (correct)
  • It cleaves mRNA after transcription is completed.

Which element is commonly recognized by the TATA-binding protein (TBP)?

  • TATA element/box (correct)
  • B recognition element (BRE)
  • Initiator element (INR)
  • Downstream promoter element (DPE)

What is the approximate length of the core promoter region?

  • 40 base pairs
  • 80 base pairs
  • 100 base pairs
  • 250 base pairs (correct)

Which element is located about 28–32 nucleotides downstream of the transcription start site?

<p>Downstream promoter element (DPE) (B)</p> Signup and view all the answers

What role do proximal promoter elements serve?

<p>They serve as binding sites for transcription factors. (D)</p> Signup and view all the answers

Which consensus sequence represents the initiator element (INR)?

<p>YYANWYY (B)</p> Signup and view all the answers

What is noted about the TATA box in eukaryotic promoters?

<p>It is present in approximately 20% of eukaryotic promoters. (D)</p> Signup and view all the answers

What is the direction in which mRNA is synthesized during elongation?

<p>5’ to 3’ (D)</p> Signup and view all the answers

What is the role of topoisomerases during transcription elongation?

<p>They relieve supercoiling of DNA. (C)</p> Signup and view all the answers

How many nucleotides can RNA Pol II incorporate into a growing RNA molecule per second?

<p>20-50 (D)</p> Signup and view all the answers

What happens to pyrophosphate (PPi) after new nucleotides are incorporated into mRNA?

<p>It is released and hydrolyzed. (A)</p> Signup and view all the answers

What is the approximate length of the DNA-RNA hybrid during transcription elongation?

<p>8-9 bp (A)</p> Signup and view all the answers

What is the main role of the proximal promoter in transcription?

<p>To enhance transcriptional activity provided by the core promoter (D)</p> Signup and view all the answers

Which element is primarily responsible for recruiting transcription factors to the promoter?

<p>CAAT Box (B)</p> Signup and view all the answers

What type of genes are typically activated by SP1?

<p>Housekeeping genes that are constitutively expressed (C)</p> Signup and view all the answers

What do Specific Response Elements allow in terms of gene expression?

<p>Regulation in response to environmental or cellular signals (B)</p> Signup and view all the answers

How do enhancers function in relation to the promoter region?

<p>They interact with TFs and coactivators to enhance transcription (A)</p> Signup and view all the answers

Which element binds hormone receptors to regulate gene expression?

<p>HRE (A)</p> Signup and view all the answers

What is a key feature of enhancer regions?

<p>They can operate at distances up to 50,000 base pairs from the start site (D)</p> Signup and view all the answers

Which factor is involved in regulating gene expression in response to cAMP levels?

<p>CREB (A)</p> Signup and view all the answers

What is the role of RNA polymerase II?

<p>To synthesize mRNA from DNA templates (C)</p> Signup and view all the answers

What role does TFIIB play in the transcription process?

<p>It initiates the formation of the pre-initiation complex. (B)</p> Signup and view all the answers

Which transcription factor is responsible for phosphorylating Serine-5 on the CTD?

<p>TFIIH (C)</p> Signup and view all the answers

What does the phosphorylation of Serine-5 in the CTD trigger?

<p>Release of RNA Polymerase II from the pre-initiation complex. (D)</p> Signup and view all the answers

What is a characteristic of the Carboxyl-terminal domain (CTD) of RNA Polymerase II?

<p>It contains a repeating domain of 7 amino acids. (C)</p> Signup and view all the answers

What does TFIID do during the transcription initiation process?

<p>It remains bound to the TATA region. (C)</p> Signup and view all the answers

Which amino acids are mainly found in the repeating domain of RNA Polymerase II's CTD?

<p>Polar and uncharged amino acids (D)</p> Signup and view all the answers

What is the effect of Serine-5 phosphorylation on the CTD?

<p>It causes RNA Polymerase II to detach from the DNA. (D)</p> Signup and view all the answers

What is the primary role of RNA Polymerase during transcription?

<p>To elongate the RNA strand. (D)</p> Signup and view all the answers

What is the nature of R groups in biological molecules during transcription?

<p>They can form hydrogen bonds with other molecules. (A)</p> Signup and view all the answers

What happens to the transcription factors once RNA Polymerase slides forward during elongation?

<p>They are no longer associated with RNA Polymerase. (A)</p> Signup and view all the answers

What is the primary function of the Pre-Initiation Complex (PIC)?

<p>To position RNA polymerase II at gene transcription start sites (A)</p> Signup and view all the answers

Which complex first binds to the TATA box during the formation of the PIC?

<p>TFIID (TBP + TAFs) (A)</p> Signup and view all the answers

What role does TFIIB play in the PIC?

<p>Provides a specific binding site for RNA Pol II (C)</p> Signup and view all the answers

What does TFIIH contribute to the Pre-Initiation Complex?

<p>Contains kinase activity and two DNA helicases (C)</p> Signup and view all the answers

What is defined as transcription initiation?

<p>Formation of a phosphodiester bond between the first two nucleotides of RNA (D)</p> Signup and view all the answers

Which protein complex binds to TFIIB in the PIC?

<p>RNA Pol II:TFIIF complex (A)</p> Signup and view all the answers

What is the primary role of TFIIF during transcription?

<p>Assisting in the elongation phase of transcription (A)</p> Signup and view all the answers

How does TFIIE assist during the formation of the PIC?

<p>By helping bind TFIIH (C)</p> Signup and view all the answers

What structural change does the PIC induce in DNA?

<p>It denatures the DNA (B)</p> Signup and view all the answers

Which aspect of RNA polymerase II does TFIIH modify during transcription initiation?

<p>It phosphorylates the tail of RNA polymerase II (A)</p> Signup and view all the answers

What is the starting material for mRNA synthesis during transcription?

<p>DNA (D)</p> Signup and view all the answers

Which enzyme is responsible for initiating transcription at a specific site on DNA?

<p>RNA polymerase II (A)</p> Signup and view all the answers

What replaces thymine (T) in the newly synthesized RNA strand?

<p>Uracil (U) (D)</p> Signup and view all the answers

What is the primary end product of transcription after processing?

<p>Messenger RNA (mRNA) (B)</p> Signup and view all the answers

Which two components are required for the translation process?

<p>mRNA and ribosomal RNA (A), tRNA and ribosomal RNA (D)</p> Signup and view all the answers

In the context of transcription, what is meant by the 'sense strand' of DNA?

<p>The strand that has the same sequence as the mRNA (C)</p> Signup and view all the answers

What is the role of transcription factors in the process of transcription?

<p>To recruit RNA polymerase to the promoter region (A)</p> Signup and view all the answers

What is the approximate length of the transcription bubble during elongation?

<p>13 bp (A)</p> Signup and view all the answers

What is released when a nucleoside triphosphate is incorporated into the growing mRNA strand?

<p>Pyrophosphate (PPi) (B)</p> Signup and view all the answers

In what direction are nucleotides incorporated into mRNA during transcription elongation?

<p>5' to 3' (A)</p> Signup and view all the answers

Which of the following statements about the DNA-RNA hybrid during transcription elongation is true?

<p>It stabilizes the elongation complex. (B)</p> Signup and view all the answers

What is the role of topoisomerases during the transcription elongation process?

<p>To relieve DNA supercoiling (D)</p> Signup and view all the answers

What is the primary function of the core promoter in eukaryotic transcription?

<p>Initiating transcriptional activity of a gene (B)</p> Signup and view all the answers

Which of the following elements is recognized by transcription factor TFIIB?

<p>B recognition element (BRE) (B)</p> Signup and view all the answers

How far upstream does the proximal promoter typically extend relative to the transcription start site?

<p>-40 to -250 base pairs (B)</p> Signup and view all the answers

What is the consensus sequence for the TATA box?

<p>TATAWAWR (D)</p> Signup and view all the answers

What role does the Downstream Promoter Element (DPE) play in transcription?

<p>Initiating gene transcription by RNA polymerase II (B)</p> Signup and view all the answers

What is the approximate percentage of eukaryotic promoters that contain the TATA box?

<p>20% (D)</p> Signup and view all the answers

Which feature distinguishes the initiator element (INR) in mammalian promoters?

<p>It overlaps with the transcription start site. (C)</p> Signup and view all the answers

Which components are essential for the binding of general transcription factors at the core promoter?

<p>The TATA box, INR, and additional motifs (A)</p> Signup and view all the answers

What general role do proximal promoter elements play in gene transcription?

<p>Regulating timing and levels of gene expression (C)</p> Signup and view all the answers

What happens to the Carboxyl-terminal domain (CTD) of RNA Polymerase II when Serine-5 is phosphorylated?

<p>It promotes the dissociation of RNA Polymerase II from the PIC. (D)</p> Signup and view all the answers

What role does TFIID play after RNA Polymerase II has begun elongation?

<p>It remains bound to the TATA box and supports new PIC formation. (D)</p> Signup and view all the answers

How does phosphorylation of Serine-5 affect RNA Polymerase II during transcription?

<p>It stimulates the elongation process. (D)</p> Signup and view all the answers

What is the primary function of TFIIH during transcription initiation?

<p>It phosphorylates the CTD of RNA Polymerase II. (C)</p> Signup and view all the answers

What effect does the phosphorylation of Serine-5 have on the CTD of RNA Polymerase II?

<p>It makes the CTD more hydrophilic. (D)</p> Signup and view all the answers

Which feature distinguishes proximal promoters from enhancers in terms of their location relative to the transcription start site?

<p>Proximal promoters are located only a few base pairs upstream. (A)</p> Signup and view all the answers

During transcription elongation, what occurs to the transcription factors that were part of the initiation complex?

<p>They are released and do not associate again. (C)</p> Signup and view all the answers

Which amino acids are primarily found in the repeating domain of the CTD of RNA Polymerase II?

<p>Polar, uncharged amino acids. (A)</p> Signup and view all the answers

What is the main function of the CAAT Box within the proximal promoter?

<p>To recruit transcription factors, increasing RNA polymerase II binding efficiency. (A)</p> Signup and view all the answers

What type of elements can Specific Response Elements respond to in gene expression regulation?

<p>Hormones, growth factors, or other signaling molecules. (C)</p> Signup and view all the answers

Which transcription factor is involved in the initial binding to the TATA box?

<p>TFIID (B)</p> Signup and view all the answers

Which transcription factor is primarily associated with the GC Box in the proximal promoter?

<p>Specificity protein 1 (SP1). (D)</p> Signup and view all the answers

What is the primary trigger for the transition from transcription initiation to elongation?

<p>Phosphorylation of Serine-5 on the CTD. (D)</p> Signup and view all the answers

How do enhancers impact the transcription process despite being located far from the core promoter?

<p>They bind coactivators and interact with the promoter to enhance transcription. (A)</p> Signup and view all the answers

What role does the Hormone Response Element (HRE) play in genetic regulation?

<p>It binds hormone receptors to mediate gene expression in response to hormones. (C)</p> Signup and view all the answers

Which of the following statements about transcription factors and proximal promoters is accurate?

<p>Some transcription factors enhance the binding efficiency of RNA polymerase II at proximal promoters. (D)</p> Signup and view all the answers

What effect do enhancer regions have on the transcription of target genes?

<p>They enhance the transcription by interacting with the promoter region. (A)</p> Signup and view all the answers

Which of the following best represents the location of the CRE (cAMP Response Element)?

<p>Within the proximal promoter region, responding to cAMP levels. (B)</p> Signup and view all the answers

What structural feature is common to enhancer regions compared to proximal promoters?

<p>Enhancer regions can act from long distances of up to 50,000 base pairs away. (D)</p> Signup and view all the answers

What synthesizes RNA using a DNA template in eukaryotic cells?

<p>RNA polymerase II (C)</p> Signup and view all the answers

Which transcription factors are essential for the assembly of the pre-initiation complex with RNA polymerase II?

<p>General Transcription Factors (A)</p> Signup and view all the answers

What characteristic of RNA Pol II allows it to synthesize mRNA in the elongation phase?

<p>It can incorporate nucleotides at a consistent rate of approximately 20-50 per second. (D)</p> Signup and view all the answers

What is the direction of RNA synthesis during transcription?

<p>5’-to-3’ (B)</p> Signup and view all the answers

What stabilizes the elongation complex during eukaryotic transcription?

<p>The DNA-RNA hybrid of approximately 8-9 base pairs. (D)</p> Signup and view all the answers

What structural feature does TFIID possess that facilitates transcription initiation?

<p>TATA-binding protein (TBP) (C)</p> Signup and view all the answers

Which RNA polymerase in eukaryotes is responsible for the transcription of ribosomal RNA?

<p>RNA polymerase I (C)</p> Signup and view all the answers

Which statements correctly describe the role of topoisomerases in transcription elongation?

<p>They release positive supercoils ahead of RNA Pol II. (A), They create negative supercoils behind RNA Pol II. (C)</p> Signup and view all the answers

Which process occurs when the 3' OH of the previous nucleotide combines with the 5' α-phosphate of an incoming nucleoside triphosphate?

<p>Release of energy during bond formation. (A)</p> Signup and view all the answers

Transcription factors function primarily to:

<p>Regulate gene expression (A)</p> Signup and view all the answers

What is the role of transcription factors like TFIIH during the pre-initiation complex formation?

<p>Phosphorylation of RNA polymerase II's CTD (D)</p> Signup and view all the answers

What is the consequence of hydrolyzing pyrophosphate (PPi) during mRNA synthesis?

<p>It serves as a source of energy for the elongation process. (C)</p> Signup and view all the answers

What is the primary function of TFIIH within the Pre-Initiation Complex?

<p>Phosphorylating sites on RNA Pol II tail to initiate elongation (B)</p> Signup and view all the answers

During the formation of the Pre-Initiation Complex, which component directly binds to the TFIIB?

<p>TFIIF (B)</p> Signup and view all the answers

Which of the following is NOT a role performed by the Pre-Initiation Complex?

<p>Facilitating DNA repair processes (D)</p> Signup and view all the answers

What is the transcription bubble formed during transcription elongation primarily composed of?

<p>Single-stranded DNA (C)</p> Signup and view all the answers

Which factor is considered necessary for the unwinding of DNA at the promoter start site during the Pre-Initiation Complex formation?

<p>TFIIH (C)</p> Signup and view all the answers

What is the primary function of the CAAT Box in the proximal promoter?

<p>Recruits transcription factors to increase RNA polymerase II binding efficiency (D)</p> Signup and view all the answers

In the context of eukaryotic transcription, what does TFIID specifically recognize?

<p>The TATA box (A)</p> Signup and view all the answers

How does TFIIA contribute to the stabilization of the Pre-Initiation Complex?

<p>By stabilizing TFIIB within the complex (D)</p> Signup and view all the answers

Which element is involved in the regulation of gene expression in response to hormones?

<p>HRE (Hormone Response Element) (D)</p> Signup and view all the answers

Enhancer regions can enhance transcription despite being located at significant distances from the promoter. What is the maximum distance disallowed for enhancer action?

<p>50,000 base pairs (D)</p> Signup and view all the answers

What is specifically defined as the initiation of transcription?

<p>The formation of a phosphodiester bond between the first two nucleotides of RNA (C)</p> Signup and view all the answers

Which component is involved in the elongation phase of transcription as part of the Pre-Initiation Complex?

<p>TFIIF (B)</p> Signup and view all the answers

Which transcription factor binds to the GC-rich sequences found in the proximal promoter?

<p>SP1 (C)</p> Signup and view all the answers

What is the approximate number of proteins that make up the Pre-Initiation Complex?

<p>100 (C)</p> Signup and view all the answers

What is the role of Specific Response Elements in gene transcription?

<p>To bind transcription factors that respond to external signals (B)</p> Signup and view all the answers

What is a unique characteristic of enhancer regions compared to proximal promoters?

<p>Enhancers can influence transcription from a significant distance away (A)</p> Signup and view all the answers

Which of the following is NOT typically a function of transcription factors binding to enhancer regions?

<p>Competing with RNA polymerase II for binding (B)</p> Signup and view all the answers

What type of genes does SP1 primarily activate?

<p>Housekeeping genes (A)</p> Signup and view all the answers

Which of the following correctly identifies a function of the CRE (cAMP Response Element)?

<p>Binds CREB, allowing regulation in response to cAMP levels (A)</p> Signup and view all the answers

Which of the following roles does TFIIH serve in relation to the Carboxyl-terminal domain (CTD) of RNA Polymerase II?

<p>Phosphorylates Serine-5 to promote elongation (B)</p> Signup and view all the answers

What biochemical change occurs to the CTD of RNA Polymerase II upon phosphorylation of Serine-5?

<p>It becomes more polar, triggering the uncoupling from the PIC (B)</p> Signup and view all the answers

Which transcription factor remains bound to the TATA box during the transcription process?

<p>TFIID (C)</p> Signup and view all the answers

How does RNA Polymerase II proceed along the DNA template during transcription elongation?

<p>It slides forward continuously while elongating the RNA (D)</p> Signup and view all the answers

What is the primary consequence of the phosphorylation of Serine-5 in the context of transcription?

<p>It promotes the continuation of elongation and mRNA capping (C)</p> Signup and view all the answers

Which amino acid sequence is characteristic of the Carboxyl-terminal domain (CTD) of RNA Polymerase II?

<p>Tyr-Ser-Pro-Thr-Ser-Pro-Ser (A)</p> Signup and view all the answers

What effect does TFIIE have during the formation of the Pre-Initiation Complex (PIC)?

<p>It helps stabilize the assembly of the transcription factors (D)</p> Signup and view all the answers

Which of the following events occurs when transcription factors dissociate from RNA Polymerase II as it elongates the RNA strand?

<p>The process of elongation takes place without interruption (D)</p> Signup and view all the answers

What is the relationship between the phosphorylation state of the CTD and the activity of RNA Polymerase II?

<p>Phosphorylation of Serine-5 activates elongation of RNA (D)</p> Signup and view all the answers

Flashcards

Gene Promoter

Region of DNA where RNA polymerase binds to start transcription, determining which DNA strand is the template.

Core Promoter

Region in DNA, ~250 base pairs upstream of the transcription start site, containing essential elements for RNA polymerase binding.

TATA box

Core promoter element with the sequence TATAWAWR, where RNA polymerase II, and transcription factors bind, crucial for transcription initiation.

Initiator element (INR)

Core promoter element overlapping with the transcription start site in mammalian RNA polymerase II-mediated transcription.

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Downstream Promoter Element (DPE)

Sequence in DNA, located downstream of the transcription start site, helping with RNA polymerase II initiation of gene transcription.

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Proximal Promoter

Sequence in DNA upstream of the core promoter, containing binding sites for specific transcription factors influencing gene expression timing and level.

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Transcription start site (TSS)

The exact location where transcription begins on a DNA strand that is converted to mRNA.

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GC Box

GC-rich sequences in the proximal promoter that are binding sites for SP1 protein, impacting the transcription of various genes.

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SP1

A transcription factor that binds to GC boxes, activating genes, especially housekeeping genes.

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Specific Response Elements

DNA sequences in the promoter region that respond to signals like hormones or growth factors, adjusting gene expression.

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Hormone Response Element (HRE)

A DNA sequence that binds hormone receptors to regulate gene expression according to hormone levels.

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cAMP Response Element (CRE)

A DNA sequence that binds CREB proteins, regulating gene expression based on cAMP levels.

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Eukaryote Transcription Enhancer

A region of DNA, often far from the start site, that increases the rate of transcription by interacting with the promoter.

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Transcription Initiation Complex

A complex of proteins assembled onto the promoter region to start transcription.

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Pre-initiation Complex (PIC)

A complex of proteins (around 100) essential for eukaryotic gene transcription.

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TFIID

A transcription factor that binds to the TATA box in the core promoter. It's composed of TBP & TAFs

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TFIIA

a transcription factor that stabilizes the PIC.

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TFIIB

a transcription factor that provides a binding site for RNA Pol II in PIC.

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RNA Pol II

The enzyme that transcribes genes to produce mRNA in eukaryotes.

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TFIIH

Helps form the PIC and contains enzymes that unwind DNA, especially using DNA helicases.

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Transcription initiation

The formation of the first phosphodiester bond in mRNA.

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Transcription Bubble

A region of unwound DNA needed for transcription. Approximately 13 base pairs in size.

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DNA-RNA Hybrid

A short, unstable double-stranded structure (8-9 base pairs) formed during transcription. This hybrid region is attached to the RNA polymerase and helps stabilize the elongation complex.

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Elongation Complex

The complete assembly of transcription machinery, including RNA polymerase, DNA, and the growing RNA transcript. It's the active unit that moves along the DNA, unwinding it and creating new RNA.

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5' --> 3' Direction

The direction in which RNA polymerase adds new nucleotides to the growing RNA transcript. RNA is synthesised by adding nucleotides to the 3' end of the RNA molecule.

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Pyrophosphate (PPi)

A molecule released during RNA synthesis when a new nucleotide is added to the growing RNA strand. It's immediately broken down into two inorganic phosphates (Pi), releasing energy which is crucial for making the RNA synthesis irreversible.

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TFIIB, TFIIE, TFIIH

Transcription factors involved in eukaryotic transcription initiation complex (PIC).

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Eukaryotic Transcription Initiation

The process of starting RNA synthesis in eukaryotes.

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RNA Polymerase II CTD

The carboxyl-terminal domain of RNA polymerase II; crucial for transcription elongation.

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Phosphorylation of CTD

The addition of a phosphate group to the CTD, a key step in promoter clearance and RNA elongation.

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Serine-5 Phosphorylation

The phosphorylation of serine-5 within the RNA polymerase II CTD.

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Transcription Factor TFIID

Transcription factor remaining bound to the promoter.

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RNA Polymerase II Elongation

Processes after transcription initiation begins.

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5' Capping of mRNA

Process of modifying mRNA after it's made, important for stability and translation.

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Carboxyl-terminal domain (CTD)

A repeating sequence of amino acids at the C-terminus of RNA polymerase II.

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Promoter clearance

The process where the transcription machinery moves away from the promoter after transcription begins.

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Central Dogma

The fundamental principle describing the flow of genetic information from DNA to RNA to protein.

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Transcription

The process of creating a messenger RNA (mRNA) copy of a gene's DNA sequence in the nucleus.

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Translation

The process of decoding the mRNA sequence to synthesize a protein in the cytoplasm.

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RNA Polymerase II

The enzyme responsible for transcribing genes into mRNA in eukaryotes.

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Promoter

A region of DNA that signals the starting point for transcription.

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Transcription Factors

Proteins that bind to the DNA sequence and help RNA polymerase II recognize the promoter and start transcription.

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HRE (Hormone Response Element)

A DNA sequence that binds hormone receptors, allowing genes to be regulated in response to hormone levels.

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CRE (cAMP Response Element)

A DNA sequence that binds CREB proteins, regulating gene expression according to cAMP levels. cAMP acts as a messenger molecule, often involved in cellular responses.

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Enhancer Region

A DNA region that can be far away from the core promoter, but still powerfully boosts the rate of transcription by interacting with the promoter.

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Transcription Factors (TFs) and Enhancers

Transcription Factors bind to enhancers, then interact with the promoter region to boost transcription by essentially facilitating the binding of the pre-initiation complex.

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What is the promoter region?

The promoter region is a specific DNA sequence where RNA polymerase binds to initiate transcription. It's like a starting point for the transcription process.

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What are core promoter elements?

Core promoter elements are DNA sequences located within 250 base pairs of the transcription start site. They're essential for binding of general transcription factors and RNA polymerase II.

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What is the TATA box?

A sequence of DNA (TATAWAWR) in the core promoter. It's the binding site for the transcription factor TBP (TATA-Binding Protein), which plays a crucial role in recruiting RNA polymerase II to initiate transcription.

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What is the INR element?

The Initiator (INR) element is a DNA sequence overlapping the transcription start site in mammalian RNA polymerase II-mediated transcription. It's recognized by TBP-Associated Factors (TAFs), which help position RNA polymerase at the start site.

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What is the DPE?

The Downstream Promoter Element (DPE) is a DNA sequence located downstream of the transcription start site. It helps RNA polymerase II initiate transcription and is recognized by TBP-Associated Factors (TAFs).

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What are proximal promoter elements?

Proximal promoter elements are DNA sequences located upstream of the core promoter, containing binding sites for specific transcription factors. These factors regulate the level and timing of gene expression.

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What are transcription factors?

Transcription factors are proteins that bind to DNA sequences in the promoter region to regulate gene expression. Some activate transcription, while others repress it.

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What is the role of BRE?

The B recognition element (BRE) is a DNA sequence adjacent to the TATA box. It's recognized by transcription factor TFIIB, which aids in stabilizing the pre-initiation complex and promoting transcription.

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What is the pre-initiation complex (PIC)?

The pre-initiation complex (PIC) is a large complex of proteins that assembles on the promoter region before transcription starts. It includes RNA polymerase II and other general transcription factors.

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TFIIH's Role

TFIIH is a transcription factor that helps assemble the pre-initiation complex (PIC) and contains enzymes that unwind DNA, particularly using DNA helicases.

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CTD's Importance

The carboxyl-terminal domain (CTD) of RNA Polymerase II is a repeating sequence of amino acids that plays a key role in transcription elongation.

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What Happens during Elongation?

During elongation, RNA Polymerase continues to slide forward along the DNA template, extending the RNA transcript, while the transcription factors from the initiation complex detach.

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What's the role of Serine-5 Phosphorylation?

Phosphorylation of serine-5 within the CTD of RNA Polymerase II makes the CTD more polar, contributing to promoter clearance and promoting RNA elongation.

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Why is 5' Capping Important?

The 5' cap is added to the mRNA molecule after it's synthesized. It's crucial for mRNA stability and efficient translation.

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What's the Function of TFIID?

TFIID is a transcription factor that binds to the TATA box in the core promoter. It's composed of TBP & TAFs.

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What does TFIID do after Transcription Initiation?

After transcription initiation, TFIID remains bound to the TATA box, allowing for the formation of additional pre-initiation complexes (PICs) to start new rounds of transcription.

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What are the 'Uncoupling' Factors?

TFIIB, TFIIE, and TFIIH are transcription factors that uncouple RNA Polymerase II from the pre-initiation complex (PIC) during elongation.

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What's the Purpose of 'Promoter Clearance'?

Promoter clearance is the process of the transcription machinery moving away from the promoter after transcription initiation, allowing for continued elongation of the RNA transcript.

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Why is Transcription Essential?

Transcription is the process by which DNA is copied into RNA. This is crucial for gene expression, as RNA is used to create proteins which carry out various functions within the cell.

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Template Strand

The DNA strand that is read by RNA polymerase to create the RNA sequence.

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General Transcription Factors

A set of proteins that are needed for RNA polymerase to initiate transcription. They bind to the core promoter region.

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Transcription Factors and Enhancers

Transcription factors bind to enhancer regions and interact with the promoter to enhance gene transcription. They essentially facilitate the binding of the pre-initiation complex.

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What does TFIID do?

TFIID is a transcription factor that binds to the TATA box in the core promoter. It is composed of TBP and TAFs, which help recruit RNA polymerase II to the promoter.

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What is TFIIH responsible for?

TFIIH is a transcription factor that helps assemble the pre-initiation complex (PIC) and contains enzymes that unwind DNA.

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What is phosphorylation of the CTD?

It's the addition of a phosphate group to the CTD of RNA polymerase II. This is crucial for promoter clearance and transcription elongation.

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What is the transcription bubble?

It's a region of unwound DNA, about 13 base pairs in size, where RNA polymerase can access the template strand to transcribe it.

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What does elongation involve?

It's the process where RNA polymerase continues to slide forward along the DNA template, extending the RNA transcript. This phase involves the removal of some of the transcription factors from the initiation complex.

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What is the function of TFIID after initiation?

After transcription initiation, TFIID remains bound to the TATA box, allowing for the formation of additional pre-initiation complexes (PICs) to start new rounds of transcription. Essentially, TFIID helps ensure that a gene can be transcribed multiple times.

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What's the role of phosphorylation of serine-5?

Phosphorylation of serine-5 within the CTD makes the CTD more polar and hydrophilic, triggering the release of RNA Polymerase II from the PIC, allowing transcription to begin.

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What is TFIID's role during elongation?

TFIID remains bound to the TATA box even after RNA Polymerase II has started transcription. This allows for new transcription initiation complexes (PICs) to form and start new transcription rounds.

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What's the importance of 5' capping?

The 5' cap is a structure added to the beginning of newly synthesized mRNA. It's essential for mRNA stability and translation (the process of turning mRNA into proteins).

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What is TFIIH's role?

TFIIH is a transcription factor that helps assemble the PIC and contains enzymes that unwind DNA (DNA helicases) to start transcription.

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What is RNA Polymerase II?

This is the enzyme responsible for transcribing genes into messenger RNA (mRNA) in eukaryotes. It reads DNA and creates a copy of the genetic code.

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Pyrophosphate (PPi) Release

During RNA synthesis, a pyrophosphate molecule is released when a new nucleotide is added to the growing RNA strand. This PPi is quickly broken down into two inorganic phosphates (Pi), releasing energy that makes the process irreversible.

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Study Notes

Molecular Mechanisms of Disease

  • The diagram displays a eukaryotic cell, highlighting its various organelles and structures.
  • Cell components like cytoskeleton (microtubules, microfilaments, intermediate filaments), centrosome, plasma membrane, secretory vesicles, lysosomes, smooth ER, peroxisomes, and mitochondria are visible.
  • The nucleus, including the nuclear pore, nuclear envelope, nucleolus, and chromatin, is also shown, along with ribosomes and the Golgi complex.

Eukaryote Gene Transcription and Translation

  • The central dogma of molecular biology describes the flow of genetic information from DNA to RNA to protein, with transcription followed by translation.
  • Transcription involves the synthesis of messenger RNA (mRNA) from a DNA template.
  • Translation is the synthesis of proteins based on the mRNA sequence.

From Genes to Proteins (Central Dogma of Molecular Biology)

  • The process is depicted as DNA undergoing transcription to create RNA, which subsequently undergoes translation into proteins.
  • DNA contains the genetic instructions for protein synthesis.
  • The process converts this information into a functional protein product.

From Genes to Proteins (Complex)

  • The illustration depicts the intricate steps of transcription and translation within a eukaryotic cell.
  • Introns are removed, and exons are joined to create mature mRNA during post-transcriptional modification.
  • The mRNA is transported out of the nucleus into the cytoplasm, where translation takes place.

From Genes to Proteins

  • Protein synthesis follows the central dogma: DNA is transcribed into RNA and then translated into proteins.
  • The process includes DNA transcription, translation, and folding.

Transcription

  • Synthesis of complementary RNA from a DNA template in the cell's nucleus.
  • Starting material is DNA.
  • Required machinery includes RNA polymerase II and transcription factors.
  • End product: messenger RNA (mRNA).

Translation

  • Synthesis of proteins in the cytoplasm, utilizing information encoded within mRNA.
  • Starting material is mRNA.
  • Required machinery includes ribosomal RNA (rRNA), ribosomal proteins, and transfer RNA (tRNA).
  • End product: polypeptide.

Sense vs Antisense DNA Strands

  • The coding strand's sequence aligns with the newly synthesized RNA sequence, except that thymine (T) is replaced by uracil (U).
  • The template strand (antisense) acts as a template for RNA synthesis.
  • Transcription creates RNA from the template strand.

Transcription (Both Strands encode genes)

  • DNA molecules comprise 3.6 x 104 base pairs (bp).
  • Both strands of DNA code for genes.
  • RNA transcripts are produced during the process.

Transcription (RNA Polymerase)

  • RNA polymerase binds to DNA, initiates transcription at the promoter region, and synthesizes RNA complementary to the DNA template.
  • Transcription factors interact with DNA to regulate transcription.
  • The promoter, a specific DNA region, is the start site for transcription.

Transcription (RNA Polymerase)

  • The process of transcription is depicted, highlighting RNA polymerase's function in transcribing DNA into RNA.
  • The crucial role of the promoter region and transcription start site (also known as +1) is highlighted.

Prokaryotes vs Eukaryotes

  • Prokaryotes have a single RNA polymerase, while eukaryotes have three (RNA polymerases I, II, and III) that perform slightly different functions in transcribing various types of RNA.
  • The three RNA polymerases in eukaryotes transcribe different types of RNA.

Eukaryote Transcription (RNA Polymerase Dependent)

  • RNA polymerase II, also called DNA-dependent RNA polymerase, synthesizes RNA in the 5'–3' direction using the 3'–5' DNA strand as the template strand.
  • Different regions, such as the core promoter, proximal elements, and enhancers, play critical roles in the regulation of gene expression.

Eukaryote Transcription (Transcription Factors)

  • Proteins combine with RNA Pol II at the promoter to create a pre-initiation complex.
  • These factors regulate gene expression.
  • General transcription factors (GTFs) assemble at the core promoter to help initiate RNA polymerase II transcription.

Eukaryote Gene Promoter

  • The promoter region on DNA is where RNA polymerase II binds before transcription starts.
  • It controls which strand is the template for mRNA.
  • Specific sequences within the promoter (core and proximal elements) regulate the rate of transcription.

Eukaryote Transcription (Core Promoter)

  • The core promoter contains crucial elements for transcription initiation, including the TATA box, initiator (Inr) sequence, and downstream promoter element (DPE).
  • This core region has specific sequences that are recognized by general transcription factors (GTFs).

Eukaryote Transcription (Core Promoter Elements)

  • The core promoter includes the initiator element (INR), which overlaps with the transcription start site.
  • It also has the downstream promoter element (DPE).
  • The core promoter's elements assist in recruiting RNA polymerase II to begin transcription.

Eukaryote Transcription (Proximal Promoter Elements)

  • Proximal promoter elements contain specific DNA sequences that bind transcription factors essential for regulating gene expression.
  • They are located near the core promoter, aiding in RNA polymerase efficiency.
  • These promoter elements are close to the core promoter, regulating the level, time, and rate of transcription initiation.

Eukaryote Transcription (Enhancer Regions)

  • Enhancer regions, located far from the promoter, play a significant role in regulating transcription.
  • They operate over long distances to modulate transcription rates.
  • Enhancer elements interact with promoter regions via protein complexes and affect transcription rates.

Eukaryote Transcription (Pre-Initiation Complex (PIC))

  • The pre-initiation complex comprises approximately 100 proteins essential for protein-coding eukaryotic gene transcription.
  • It is multifaceted, incorporating components like transcription factors, coactivators, and the RNA polymerase.
  • Basal transcription factors, like TFIIA and TFIIB, position RNA Pol II at transcription start sites and facilitate DNA denaturation essential for RNA synthesis.

Eukaryote Transcription (Formation of the Pre-Initiation Complex (PIC))

  • Formation of the PIC entails various steps, including TFIID binding to the TATA box, followed by TFIIB binding, and recruitment of RNA polymerase II.
  • All these are pivotal steps in facilitating accurate gene transcription processes

Eukaryote Transcription (Initiation)

  • Defining transcription initiation pertains to the formation of the bond between the initial nucleotides of the RNA transcript.
  • RNA polymerase continues to add nucleotides to the RNA strand in the 5' to 3' direction.
  • Factors no longer associated with the complex are released after initiation.

Eukaryote Transcription (Elongation)

  • The elongation process involves extending the RNA transcript using the DNA template.
  • RNA polymerase II incorporates nucleotides at a rate of ~20-50 per second.

Eukaryote Transcription (Elongation Factors)

  • Several transcription factors, including P-TEFb, play vital roles in the elongation phase.
  • These factors assist further in the elongation process and help in transcription control.

Eukaryote Transcription (Termination)

  • Eukaryotic transcription lacks defined termination sequences like those found in prokaryotes. Instead, termination often occurs through polyadenylation signal sequences in the RNA transcript.
  • The process involves cleavage of the RNA transcript and addition of a poly-A tail to the 3' end to finalize the mRNA molecule.

Biological Molecules (Proteins)

  • Amino acid R-groups exhibit varying charges and polarities, influencing their interactions and roles in protein function.
  • Some R-groups are polar uncharged in nature, while others are acidic or basic, significantly influencing their roles in protein function and interaction.

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HSS2305A 2024 Lecture 8 PDF

Description

Explore the intricate details of eukaryotic cells and the processes of gene transcription and translation. This quiz examines the organelles involved in these molecular mechanisms and illustrates the central dogma of molecular biology. Test your knowledge on how genetic information flows from DNA to RNA to protein.

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