L2 Transcription of Eukaryotic Genes
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Questions and Answers

Which RNA polymerase is responsible for the transcription of mRNA?

  • RNA polymerase I
  • RNA polymerase II (correct)
  • RNA polymerase III
  • None of the above

    • All genes are transcribed in every cell.

    False

    What is the central dogma of molecular biology?

    DNA -> RNA -> Protein

    Transcription proceeds at _____ nt/sec.

    <p>33-50</p> Signup and view all the answers

    Match the following RNA polymerases with their primary function:

    <p>RNA polymerase I = Ribosomal RNA RNA polymerase II = Messenger RNA RNA polymerase III = Transfer RNA RNA polymerase IV = Non-coding RNA</p> Signup and view all the answers

    What is the role of the polyA signal in transcription?

    <p>Terminates transcription</p> Signup and view all the answers

    Transcription requires a primer to begin.

    <p>False</p> Signup and view all the answers

    What is the role of transcription factors in the transcription initiation complex?

    <p>They help RNA polymerase bind to the promoter.</p> Signup and view all the answers

    Which transcription factors are involved in preventing TFIID rebinding?

    <p>TFIIH and TFIIE</p> Signup and view all the answers

    TFIIH XPB facilitates the closing of DNA during transcription initiation.

    <p>False</p> Signup and view all the answers

    What event causes abortive initiation to turn into productive elongation?

    <p>CTD-S5 phosphorylation</p> Signup and view all the answers

    Capping is performed by three enzymatic steps, including removal of phosphate, addition of GTP, and __________ of Guanosine.

    <p>methylation</p> Signup and view all the answers

    Match the following transcription factors with their functions:

    <p>TFIIH = Translocates to help open DNA TFIIE = Recruits other transcription factors TFIIB = Increases bending and supercoiling CTD = Coordinates binding of transcription factors</p> Signup and view all the answers

    What influences the speed of transcription elongation?

    <p>Fast trigger loops</p> Signup and view all the answers

    Kinases can alter CTD phosphorylation patterns in a way that affects which proteins can recognize and bind to it.

    <p>True</p> Signup and view all the answers

    What is the range of transcription elongation speed?

    <p>1500-2700 bp/min</p> Signup and view all the answers

    What is the role of TATA binding protein in transcription initiation?

    <p>It binds and kinks DNA, facilitating polymerase access.</p> Signup and view all the answers

    The major groove of DNA provides fewer interactions for proteins than the minor groove.

    <p>False</p> Signup and view all the answers

    Name the common element required for the expression of a structural gene in eukaryotes.

    <p>promoter</p> Signup and view all the answers

    The distance between TBP and TFIID is approximately ______ bp.

    <p>32</p> Signup and view all the answers

    Match the following components with their functions:

    <p>BRE = Binds to TFIIB INR = Delivers TBP to DNA DPE = Part of TFIID TFIID = Establishes sequence specificity</p> Signup and view all the answers

    What sequences signal the beginning and end of an intron?

    <p>GU at the beginning and AG at the end</p> Signup and view all the answers

    Which protein complex is recruited to bind the BRE during transcription initiation?

    <p>TFIIB</p> Signup and view all the answers

    Capping of mRNA occurs at the 3' end to prevent degradation.

    <p>False</p> Signup and view all the answers

    Transcription initiation does not require any protein binding to DNA.

    <p>False</p> Signup and view all the answers

    What stabilizes the tight binding of DNA binding proteins during transcription initiation?

    <p>Weak interactions such as hydrogen-bonds, hydrophobic, or electrostatic interactions.</p> Signup and view all the answers

    What is the role of untranslated regions (UTRs) in mRNA?

    <p>UTRs help regulate export and other processes.</p> Signup and view all the answers

    The process of __________ involves cleavage and polyadenylation at the 3' end of mRNA.

    <p>termination</p> Signup and view all the answers

    Match the following terms with their descriptions:

    <p>Capping = Prevents degradation from 5' to 3' Splicing = Removes non-coding intronic sequences Xrn2 = Exonuclease that degrades RNA Pol II = Transcribes protein-coding and non-coding RNA</p> Signup and view all the answers

    What effect does the Spt5 elongation factor have on RNA Polymerase II?

    <p>It slows down the transcription process</p> Signup and view all the answers

    Study Notes

    Overview of Eukaryotic Gene Transcription and Processing

    • RNA plays a critical role in gene expression, serving as a messenger that transmits information from DNA in the nucleus to the cytoplasm.
    • Central dogma of molecular biology: DNA → RNA → Protein.
    • Transcription involves copying DNA sequence information into RNA, facilitated by DNA-dependent RNA polymerases.

    RNA Polymerases in Eukaryotes

    • RNA Polymerase I: Transcribes ribosomal RNA (rRNA), accounting for about 50% of total RNA; essential for ribosome structure.
    • RNA Polymerase II: Responsible for synthesizing messenger RNA (mRNA) and non-coding RNAs, comprising roughly 3% of RNA.
    • RNA Polymerase III: Transcribes transfer RNA (tRNA) and some catalytic RNAs, constituting about 15% of RNA.

    Transcription Initiation

    • Initiation occurs at a specific promoter region and ends at a polyA signal.
    • Eukaryotic cells only express a small subset of the 21,300 protein-coding genes, typically around 5,000 per cell.

    Components of the Transcription Initiation Complex

    • Transcription factors bind to DNA to enable RNA Polymerase II (Pol II) binding.
    • Consensus sequences are specific nucleotide patterns that enhance transcription efficiency.
    • Key elements include:
      • TATA Binding Protein (TBP): Bends DNA to facilitate binding of Pol II.
      • TFIID: A protein complex that includes TBP and various associated factors, vital for recognizing promoter elements.

    Steps of Preinitiation Complex Assembly

    • TBP binds to the promoter and kinks DNA, allowing access for other transcription factors.
    • Other factors, such as TFIIB and Pol II-TFIIF, are recruited sequentially.
    • The assembly of the preinitiation complex is tightly regulated to avoid premature transcription.

    Transcription Elongation

    • Initiation turns into productive elongation after phosphorylation of the C-terminal domain (CTD) of RNA polymerase.
    • Elongation rates range from 1,500 to 2,700 nucleotides per minute.
    • CTD phosphorylation regulates the binding of transcription factors and facilitates RNA processing.

    RNA Processing Post-Transcription

    • Capping involves:
      • Removal of phosphate from the 5' end of the RNA.
      • Addition of guanosine triphosphate (GTP).
      • Methylation of guanosine to protect against degradation.
    • Splicing removes non-coding introns, characterized by specific GU-AG sequences.
    • Mature mRNA contains a coding sequence and 5' and 3' untranslated regions (UTRs) that assist in export and regulation.

    Transcription Termination

    • Termination requires processing of the 3' end, including cleavage and polyadenylation.
    • The cleavage/polyadenylation complex assembles on the RNA to ensure proper termination.
    • Exonuclease Xrn2 degrades residual RNA post-termination, while Pol II can modulate elongation rates through various factors.

    Important Notes

    • Not all transcription factors are needed for transcribing chromatin-associated DNA, whereas naked DNA requires more general transcription factors.
    • Transcription is a highly coordinated and regulated process, integrating multiple signals for efficiency and fidelity.

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    Related Documents

    L2 Transcription and Processing of Eukaryotic Genes

    Description

    This quiz explores the transcription process of eukaryotic genes, focusing on the role of RNA in gene expression and the components of the transcription initiation complex. It delves into the mechanisms of mRNA processing and the order of transcription initiation in eukaryotes. Test your understanding of these key concepts in molecular biology!

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