BIOL 366 Lecture 15: Gene Expression in Eukaryotes I
22 Questions
1 Views

Choose a study mode

Play Quiz
Study Flashcards
Spaced Repetition
Chat to lesson

Podcast

Play an AI-generated podcast conversation about this lesson

Questions and Answers

What role does the Gal4 protein play in the activation of eukaryotic genes?

  • It serves as a transcription activator by recruiting the Pol II complex to regulatory sites. (correct)
  • It functions as a coactivator by interacting directly with RNA Polymerase.
  • It represses transcription by blocking access to the promoter.
  • It binds directly to the promoter region and initiates transcription.

    • Which type of proteins are required at every Pol II promoter in eukaryotic gene transcription?

  • Repressors
  • Activators
  • General transcription factors (correct)
  • HMG proteins

    • HMG proteins play a critical role in eukaryotic gene expression by:

  • Inhibiting the function of coactivators.
  • Bringing distant DNA regulatory elements near the promoter. (correct)
  • Encoding the components of the RNA Polymerase II complex.
  • Binding directly to the promoter region to enhance transcription.

    • Which of the following statements correctly describes a function of coactivators in eukaryotic transcription?

    <p>They act as a bridge between activators and the RNA Polymerase complex.</p> Signup and view all the answers

    In the context of gene repression mechanisms in eukaryotes, which of the following roles do repressors typically perform?

    <p>Block the binding of activators to enhancer regions.</p> Signup and view all the answers

    What is the role of GAL80 protein in the regulation of GAL gene expression without galactose?

    <p>It binds to Gal4p, inhibiting its activation of Pol II.</p> Signup and view all the answers

    During the presence of galactose, what is the function of Gal3p in the regulation of GAL genes?

    <p>It alters the conformation of Gal80p to inactivate it.</p> Signup and view all the answers

    Which of the following accurately describes the DNA-binding domain of HMG proteins?

    <p>It consists of a helix-loop-helix type structure known as HMG-box.</p> Signup and view all the answers

    What is the primary role of transcription repressors in eukaryotic gene regulation?

    <p>To bind specific sequences and inhibit transcription or disrupt activator interactions.</p> Signup and view all the answers

    Which of the following structural GAL genes are responsible for the metabolism of galactose in yeast?

    <p>GAL1, GAL10, GAL2, and GAL7</p> Signup and view all the answers

    What is the significance of the TATA box in the promoters of GAL genes?

    <p>It is essential for the recruitment of RNA polymerase II.</p> Signup and view all the answers

    What happens to Gal4p when Gal80p is inactivated by Gal3p upon galactose presence?

    <p>Gal4p can bind Pol II and activate transcription.</p> Signup and view all the answers

    What is the key feature of the Mobility Shift Assay when assessing the binding of TF-x to the promoter region of Gene-Y?

    <p>It detects changes in DNA mobility in the presence of TF-x.</p> Signup and view all the answers

    What is the underlying mechanism that allows genetic imprinting to affect gene expression?

    <p>It involves the methylation of cytosine residues on one of the parental alleles.</p> Signup and view all the answers

    Which mechanism describes the inactivation of one X chromosome in female mammals?

    <p>Barr body formation via chromatin condensation.</p> Signup and view all the answers

    How does traditional Mendelian inheritance differ from genetic imprinting?

    <p>Imprinting showcases inheritance independent of the Mendelian rules of segregation.</p> Signup and view all the answers

    What is the role of CTCF in the regulation of the IGF2 gene?

    <p>CTCF's binding to the insulator prevents the transcription of IGF2.</p> Signup and view all the answers

    What occurs in the yeast two-hybrid assay?

    <p>Interaction between proteins is detected through reporter gene activation.</p> Signup and view all the answers

    What is a common outcome of dosage compensation in organisms with sex chromosomes?

    <p>Complete silencing of one X chromosome in females leading to a Barr body.</p> Signup and view all the answers

    Which statement accurately reflects the concept of dosage compensation?

    <p>It regulates the expression of genes on sex chromosomes to prevent imbalance.</p> Signup and view all the answers

    What is the significance of the Yeast GAL Expression System in gene regulation?

    <p>It allows for the study of transcriptional activation through galactose utilization.</p> Signup and view all the answers

    Which regulatory mechanism is characterized as being epigenetic in nature?

    <p>Genetic imprinting involving methylation of cytosine residues.</p> Signup and view all the answers

    Study Notes

    BIOL 366 Lecture 15: Gene Expression in Eukaryotes I

    • Lecture covers the yeast Gal operon and its applications, plus regulatory mechanisms unique to eukaryotes.
    • Text section is 21.1.1–21.3.
    • Slides will be updated before the Tuesday lecture.

    Announcements

    • Exam III is on November 22nd, with a review/questions on November 20th.
    • Exam is cumulative, covering lectures 1–15.
    • Exam format is like midterm II, including multiple-choice and written questions.
    • Exam is 60 minutes long, similar to midterm II.
    • Review will be next Tuesday.
    • Two to three more assignments will be given on remaining lectures.
    • Final exam is cumulative, with 50% of the final grade based on material after Exam II and 50% before Exam II, weighting each lecture equally.

    Eukaryotic Promoters

    • Eukaryotic promoters vary in complexity.
    • More complex organisms have more complex promoters and control elements.
    • Changes in gene expression occur during development, intercellular communication, and interaction with the environment.
    • Mammalian gene promoters range from -50 to -10 kilobases (-kbp) to +10 to +50 kbp.
    • Yeast gene promoters range from -250 to +1.

    Eukaryotic RNA Polymerases

    • All three eukaryotic RNA polymerases have little to no affinity for their promoters.
    • They almost always require activator and coactivator proteins.

    Regulatory Proteins

    • General transcription factors are always required.
    • DNA-binding transcription activators (transactivators) are important.
    • DNA-binding transcription coactivators also play a role.
    • Repressors are used in some cases.
    • TFIID is a crucial general transcription factor.

    Activation of Eukaryotic Genes

    • General (basal) transcription factors are proteins required for every Pol II promoter.
    • They bind the promoter region near the gene.
    • Example: TATA binding Protein (TBP).
    • Upstream Activating Sequences (UAS) are regulatory sites in yeast.
    • Activators bind distant regulatory sites (enhancers in higher eukaryotes), recruiting Pol II complex to the promoter.
    • Example: Gal4 in yeast.
    • Coactivators function as bridges between activators and RNA Pol II.
    • They do not directly interact with DNA.
    • Example: Mediator and TFIID.
    • High-Mobility Group (HMG) proteins bend DNA, leading to looping between enhancers and promoters, their binding is non-specific.

    Repression of Eukaryotic Genes

    • Repressors bind specific DNA sequences and inhibit transcription.
    • They may disrupt contacts between Pol II and activators or coactivators.

    Yeast GAL Expression System

    • GAL genes allow yeast to take in and metabolize galactose.
    • There are four structural Gal genes (GAL1, GAL10, GAL2, and GAL7) located in different genome loci, controlled by the same regulatory proteins.
    • There are three regulatory genes:
      • GAL4: DNA-binding transcription activator (transactivator)
      • GAL80: Repressor
      • GAL3: Ligand (galactose) sensor
    • GAL gene promoters consist of a TATA box and one or more upstream activator sequences (UASGAL).
    • UASGAL site is recognized by the Gal4 protein, a DNA-binding transactivator.

    Roles of Gal3p, Gal4p, and Gal80p

    • Gal4p binds UASGAL; Gal80p prevents Gal4p's activation of Pol II in the absence of galactose.
    • Gal3p, activated by galactose, binds Gal80p, changing its conformation, and inactivating it.
    • This releases Gal4p, allowing it to bind Pol II, activating transcription.

    Yeast Two-hybrid Assay

    • A method to detect protein-protein interactions using Gal4 protein and yeast GAL genes.
    • A reporter gene is placed under GAL promoter control.
    • DNA-binding domain of Gal4 is fused to protein X; RNA polymerase-activating domain fused to protein Y.
    • If proteins X and Y interact, DNA-binding and activation domains of Gal4 come together, activating the GAL promoter.

    Other Transcription Factors

    • Some transcription factors (TFs) form functional heterodimers.
    • Most eukaryotic TFs bind DNA as homodimers.
    • However, structurally related eukaryotic transcription factors can form heterodimers.
    • Hypothetical family of four different but related proteins could form up to 10 different dimeric species.
    • Each dimeric species may have unique activity.
    • Example: mammalian AP-1 TFs (e.g., Fos, Jun) control cell proliferation and differentiation.
    • AP-1 family members have basic leucine zipper types for protein dimerization and DNA binding.

    Mobility Shift Assay

    • Used to determine if a transcription factor (TF-x) binds to a promoter region of a gene (gene-Y).
    • Purified TF-x is mixed with labeled genomic DNA fragment from gene-Y, run on a polyacrylamide gel, and visualized.
    • Changes in DNA mobility indicate TF-x binding.

    Two Regulatory Mechanisms Unique to Eukaryotes

    • Genetic Imprinting: Some eukaryotes turn expression of specific alleles from one parent on and off. It is an epigenetic process based on methylation of cytosine residues and is independent from Mendelian inheritance.
    • Dosage Compensation: Maintaining equal gene expression levels between sexes with different sized chromosomes (XX females and XY males). Three mechanisms exist that deal with this regulation.

    Studying That Suits You

    Use AI to generate personalized quizzes and flashcards to suit your learning preferences.

    Quiz Team

    Related Documents

    Lecture 15 - Gene Exp in Eukaryotes I PDF

    Description

    This lecture focuses on the yeast Gal operon and highlights the unique regulatory mechanisms of gene expression in eukaryotes. It encompasses sections 21.1.1 to 21.3, providing insights into eukaryotic promoters and their complexities. Prepare for Exam III with a cumulative review of lectures 1–15 leading up to the final.

    More Like This

    Use Quizgecko on...
    Browser
    Open
    Browser
    Browser