lec 30

Eukaryotic Gene Regulation Overview

  • Terminology:

    • Enhancer

    • Silencer

    • Promoter

    • Activator

  • Learning Objectives:

    • LO63: Create a model for eukaryotic gene expression using knowledge of chromatin, promoters, and enhancers. Identify protein expression regulation steps.

    • LO64: Explain how transcription factor gradients create gene expression stripes in embryos.

Gene Regulation Mechanisms

  • Gene Expression Steps in Eukaryotes:

    1. Gene location in nucleus

    2. Chromatin remodeling

    3. Transcription

    4. mRNA splicing

    5. mRNA export to cytoplasm

    6. mRNA stability & localization

    7. Translation

    8. Protein modification

  • Chromatin and Gene Regulation:

    • Nucleosomes restrict transcription factor access.

    • Promoters often are nucleosome-free regions (NFR).

    • Chromatin remodeling is energy-dependent and exposes regulatory DNA.

  • Histone Modifications Influence:

    • Acetylation facilitates transcription by neutralizing histones' positive charges, reducing DNA binding affinity.

Cis-Regulatory Elements

  • Types:

    • Promoters: near genes; contain core & proximal elements.

    • Enhancers: can be distal, function regardless of orientation; activate gene expression.

    • Silencers: repress expression like enhancers.

  • Transcription Factors:

    • Interact with cis-acting sequences; can be activators or repressors.

    • Contain DNA-binding and regulatory domains.

Example: Drosophila Even-Skipped Gene

  • Expressed in stripes regulated by specific enhancers.

  • Utilizes a combination of positive and negative regulators for spatial expression.

  • Cis-Regulatory Codes:

    • Direct gene expression in different developmental contexts (CNS, muscle, gut).

Suggested Practice Problems

  • Chapter 17: 4, 6, 7, 10, 11, 12

  • Chapter 17: 21, 22, 25

  • Midterm Exam: Covering Lectures 22-33. Due November 20-23.