Summary of LAQ- Regulation of Gene Expression in Eukaryotes

Key Concepts and Mechanisms of Gene Regulation in Eukaryotes

• Types of Genes:
  • Housekeeping Genes: Constitutively expressed genes necessary for basic cellular functions.
  • Inducible Genes: Genes that are regulated and expressed in response to specific stimuli.
• Levels of Regulation:
  • DNA Level:
    • Epigenetic Modifications: Chemical modifications (e.g., acetylation and methylation of histones) that alter gene expression without changing the DNA sequence.
    • Gene Amplification: Increasing the number of copies of a gene, e.g., dihydrofolate reductase in cancer therapy leading to drug resistance.
    • Gene Rearrangement: Genetic rearrangements that allow for the production of diverse antibodies (e.g., immunoglobulin genes).
  • Transcription Level:
    • Promoter and Enhancer Regions: Specific DNA sequences that facilitate the binding of RNA polymerase and Transcription Factors.
    • Transcription Factors: Proteins that bind to DNA and regulate transcription, including TATA-binding protein and various Transcription Factors (TF2A, TF2B, etc.).
    • DNA Binding Motifs: Structural motifs (e.g., zinc finger, leucine zipper, helix-turn-helix) that facilitate the interaction between Transcription Factors and DNA.
  • Post-Transcriptional Modifications:
    • Splicing: The process of removing introns and joining exons in mRNA.
    • Selective Splicing: Joining specific exons to produce different mRNA variants.
    • Alternative Splicing: Using different splice sites to create diverse mRNA products.
    • mRNA Editing: Modifications that change the coding sequence, e.g., conversion of CAA to UAA resulting in different protein products (APO B48 vs. APO B100).
    • mRNA Stability: Mechanisms that enhance the stability of mRNA, such as the iron regulatory protein's interaction with the transferrin receptor mRNA.
  • Translational Regulation:
    • Eukaryotic Initiation Factors (eIF): Proteins that play critical roles in the initiation of translation, regulated by phosphorylation.
    • Post-Translational Modifications: Changes to proteins after translation, such as proteolysis and glycosylation.

Summary of Mechanisms

• At the DNA Level:
  • Epigenetic Modifications (acetylation increases gene expression; methylation decreases it).
  • Gene Amplification (e.g., resistance to Methotrexate).
  • Gene rearrangement (e.g., antibody diversity).
• At the Transcription Level:
  • Role of promoter and enhancer regions.
  • Importance of Transcription Factors and their binding motifs.
• Post-Transcriptional Modifications:
  • Splicing, selective splicing, alternative splicing, mRNA editing, and mRNA stability.
• Translational Regulation:
  • Role of eIF2 and eIF4E in translation initiation.

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