Transcriptional Regulation in Eukaryotes
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Questions and Answers

Which component plays a crucial role in the activation of transcription in eukaryotes?

  • Ribosomes
  • Introns
  • Exons
  • Transcription factors (correct)

    • How does chromatin structure influence gene transcription?

  • It allows the transcription apparatus to easily access genes. (correct)
  • It converts genes into RNA.
  • It has no impact on transcription.
  • It restricts transcription factors from accessing the DNA.

    • What is the role of histone acetyltransferase (HAT) in transcriptional regulation?

  • To directly transcribe DNA into mRNA.
  • To inhibit transcription by tightening chromatin structure.
  • To modify histones and loosen chromatin for transcription activation. (correct)
  • To promote the binding of non-coding RNA.

    • What is indicated by DNase hypersensitivity in chromatin?

    <p>Nucleosomes are cleared, indicating active chromatin.</p> Signup and view all the answers

    Which mechanism is NOT involved in transcription activation?

    <p>RNA degradation</p> Signup and view all the answers

    What effect do extracellular stimuli typically have on gene transcription?

    <p>They can enhance or suppress transcription.</p> Signup and view all the answers

    How do intermolecular interactions contribute to gene regulation?

    <p>They can stabilize or destabilize the transcription apparatus.</p> Signup and view all the answers

    What defines the role of an adaptor protein in transcriptional regulation?

    <p>It serves as a mediator linking transcription factors and the transcription machinery.</p> Signup and view all the answers

    What role does acetylation play in histone modification?

    <p>Promotion of gene activation</p> Signup and view all the answers

    Which post-translational modification is associated with transcription and cell division?

    <p>Phosphorylation of lysines</p> Signup and view all the answers

    What is a characteristic feature of a class II regulatory region enhancer?

    <p>Can interact with polymerase regardless of orientation</p> Signup and view all the answers

    Which complex is involved in recruiting histone acetylase during transcriptional activation?

    <p>Mediator complex</p> Signup and view all the answers

    What is the effect of methylation on histones?

    <p>Can lead to gene repression</p> Signup and view all the answers

    Which of the following describes the general role of transcription factors in eukaryotic transcription activation?

    <p>They can co-operate with RNA polymerase and interact with distal elements</p> Signup and view all the answers

    What is a critical function of signal transduction pathways in relation to transcription?

    <p>They phosphorylate transcription factors to alter transcription activity</p> Signup and view all the answers

    Which of the following is true regarding the interaction of DNA with transcription factors?

    <p>Multiple binding sites for transcription factors can exist in enhancers and promoters</p> Signup and view all the answers

    What role does cAMP play in transcription activation?

    <p>It activates protein kinases which regulate gene activation.</p> Signup and view all the answers

    Which mechanism allows steroid hormones to influence gene expression?

    <p>They diffuse through the plasma membrane and bind specific receptors.</p> Signup and view all the answers

    How do enhancers affect transcription?

    <p>They recruit transcription factors that enhance gene activation.</p> Signup and view all the answers

    What is the bipartite nature of transcription factors?

    <p>They consist of a DNA-binding domain and an activation domain.</p> Signup and view all the answers

    What must happen to chromatin for transcription factors to access DNA?

    <p>Chromatin must be modified to become more accessible.</p> Signup and view all the answers

    Which subfamily of nuclear hormone receptors is characterized by their ability to form heterodimers?

    <p>Thyroid hormone receptors</p> Signup and view all the answers

    How do signal transduction pathways typically influence gene transcription?

    <p>By modulating the activity of transcription factors through phosphorylation.</p> Signup and view all the answers

    What is the function of co-activators in transcription regulation?

    <p>They assist transcription factors in recruiting RNA polymerase.</p> Signup and view all the answers

    Which of the following statements is accurate regarding the role of chromatin structure in transcription?

    <p>Transcription requires chromatin to be in a more relaxed state.</p> Signup and view all the answers

    What effect does ligand binding have on nuclear hormone receptors?

    <p>It facilitates the translocation of the receptor to the nucleus.</p> Signup and view all the answers

    What is the primary purpose of the 5' capping process in mRNA?

    <p>To increase stability and assist in translation initiation</p> Signup and view all the answers

    What is the role of polyadenylation in mRNA processing?

    <p>To enhance nuclear export and translational efficiency</p> Signup and view all the answers

    Which of the following is a necessary step during the splicing of pre-mRNA?

    <p>Cleavage at specific sites</p> Signup and view all the answers

    Which sequence is recognized as a signal for cleavage and polyadenylation in eukaryotic mRNA?

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

    Which mechanism allows for multiple functions to be derived from a single gene?

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

    What is the result of methylation at the 2' position of the first two nucleotides during mRNA capping?

    <p>Enhances translation efficiency</p> Signup and view all the answers

    What is the relationship between transcription initiation and mRNA capping?

    <p>Capping is linked to the initiation of transcription</p> Signup and view all the answers

    Which factor is involved in the cleavage of pre-mRNA during polyadenylation?

    <p>PolyA polymerase</p> Signup and view all the answers

    What is the role of U2, U5, and U6 in the spliceosome?

    <p>They form the active site of the spliceosome.</p> Signup and view all the answers

    What is the significance of alternative splicing?

    <p>It generates diverse protein isoforms from a single gene.</p> Signup and view all the answers

    What processing event involves the addition of a poly(A) tail?

    <p>3' cleavage</p> Signup and view all the answers

    What is the main function of the spliceosome during RNA processing?

    <p>To excise introns and ligate exons.</p> Signup and view all the answers

    What are snRNPs primarily composed of?

    <p>Small nuclear RNA and proteins.</p> Signup and view all the answers

    How does splicing affect gene expression?

    <p>It allows for the formation of multiple protein variants.</p> Signup and view all the answers

    What role does catalytic RNA play in RNA splicing?

    <p>It facilitates the splicing reaction.</p> Signup and view all the answers

    Which component is considered a splice donor during spliceosome assembly?

    <p>U1</p> Signup and view all the answers

    What is the primary role of the cleavage stimulatory factor (CstF) in the pre-mRNA processing?

    <p>It recruits cleaving factors and poly-A polymerase.</p> Signup and view all the answers

    In the splicing mechanism, what is the purpose of the lariat formation?

    <p>To allow the intron to be removed efficiently.</p> Signup and view all the answers

    Which of the following describes a key feature of 5' and 3' splice sites?

    <p>They possess unique conserved sequences that are recognized by spliceosomal components.</p> Signup and view all the answers

    What is the function of small nuclear ribonucleoprotein particles (snRNPs) in the splicing process?

    <p>They catalyze the cleavage and joining of RNA sections.</p> Signup and view all the answers

    Which factor is crucial during the first step of splicing?

    <p>Cleavage at the 5' splice site.</p> Signup and view all the answers

    What is the significance of the poly-A tail linked to transcription?

    <p>It plays a major role in the stability of mRNA.</p> Signup and view all the answers

    During splicing, how do conserved sequences affect the intron removal process?

    <p>They facilitate the binding of spliceosomal proteins.</p> Signup and view all the answers

    Which sequence is recognized as the branch point in splicing?

    <p>A specific sequence of adenine followed by pyrimidines.</p> Signup and view all the answers

    Study Notes

    Aims of the Lecture

    • Describe mechanisms of transcription activation
    • Explain the role of chromatin in transcription activation
    • Demonstrate how intermolecular interactions regulate gene expression
    • Describe how external stimuli alter gene transcription

    Transcriptional Regulation in Eukaryotes

    • Chromatin structure is crucial
    • Transcription factors are key elements in activation processes
    • Activation mechanisms are important aspects for a detailed understanding
    • Key terms include histone, nucleosome, chromatin, histone acetyltransferase (HAT), adaptor, and mediator proteins

    Eukaryotic DNA Organization

    • Eukaryotic DNA is highly organized into chromatin
    • The transcription apparatus needs access to genes

    DNase Hypersensitivity and Gene Activation

    • Nucleosomes are removed from active chromatin, either by sliding or eviction
    • This process is crucial for gene expression

    Histone Structure

    • Highly conserved within eukaryotes
    • Rich in basic amino acids like lysine and arginine
    • General structure is similar across different organisms

    Nucleosome Structure

    • Detailed visual representations of nucleosome structure are provided

    Post-translational Modification of Histones

    • Methylation, acetylation, and phosphorylation alter histone function and influence gene expression:
      • Methylation: Gene activation/repression, DNA replication, nucleosome assembly
      • Acetylation : Gene activation, DNA replication, nucleosome assembly
      • Phosphorylation: Cell division, transcription, chromatin structure

    Class II Regulatory Region

    • Regulatory regions such as enhancers and promoters
    • Regions contain specific binding sites for transcription factors which interact with polymerase
    • Position and orientation of these components are important

    Transcriptional Stimulation in Eukaryotes

    • Long-distance interactions involving DNA bending/looping
    • General (basal) factors and polymerase recruitment is crucial along with recruitment/co-recruitment of HATs and chromatin modifier complexes

    Signal Transduction Pathways

    • Ligand-receptor interactions at the plasma membrane
    • Generation of second messenger molecules (e.g., cAMP)
    • Activation of protein kinases leading to regulation of transcription factor activity and resultant protein-protein interactions
      • Transcription factor activity and interactions regulated by Charge, structure, protein-protein interactions
      • Nuclear localization, degradation, DNA binding, and activation are controlled to influence gene expression

    Activation of Transcription by Signal Transduction

    • Examples of signal transduction pathways relevant to gene activation such as activation in response to viral infection or cyclic AMP mediated responses, including specific examples such as CREB and its regulation by cyclic AMP.

    Nuclear Hormone Receptors

    • Large superfamily of ligand-dependent transcription factors
    • Subfamilies include homodimers, heterodimers, and monomers
    • Examples of hormones such as estrogens, androgens, corticosteroids, retinoids, thyroid hormone, vitamin D, ecdysone, fatty acids, prostaglandins
    • Key aspects include ligand binding, receptor translocation to the nucleus, and activation of transcription

    C4 Zinc Fingers

    • Protein domains in nuclear hormone receptor family
    • Exhibit key DNA-binding function

    Keywords and Concepts

    • Chromatin structure modification for transcription factor access
    • Promoters and enhancers binding transcription factors
    • Recruiting polymerases and modifying chromatin
    • Signaling pathways and transcriptional factor/gene activation

    Learning Outcomes

    • Define and describe the components of a eukaryotic transcriptional regulatory sequence
    • Understand structure and bipartite nature of sequence-specific transcription factors
    • Understand the role of chromatin and the basal transcription apparatus in transcription activation
    • Understand how signal transduction pathways influence gene transcription
    • Understanding of nuclear hormone receptors, their regulation by phosphorylation and their function in gene activation

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    Description

    Explore the mechanisms of transcription activation and the critical role of chromatin in gene expression. This quiz covers concepts such as nucleosome organization, the action of transcription factors, and how external stimuli impact transcription processes. Test your understanding of histones, chromatin structure, and gene regulation.

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