Gene Regulation in Eukaryotes

Lecture 2 Overview

• Eukaryotic gene expression overview
• Eukaryotic RNA polymerases and gene promoters are discussed
• The lecture utilizes material from Molecular Cell Biology, Eighth Edition, Chapter 9.

SLGS (Supported Learning Groups) Sessions

• Amara's sessions are Tuesdays and Thursdays, 1:00 PM - 2:30 PM in LIB 246A.
• Leah's sessions are Tuesdays and Thursdays, 4:00 PM - 5:30 PM in LIB 246A.
• Jack's sessions are Mondays and Wednesdays, 3:00 PM - 4:30 PM in LIB 109.
• Sena's sessions are Mondays and Wednesdays, 1:30 PM - 3:00 PM in LIB 109.

Eukaryotic Gene Control

• The primary function of eukaryote gene regulation is for precise developmental and tissue-specific programs to execute the proper genes at the proper times during development and cell differentiation.
• Students should watch an animation called 'Eukaryotic Transcriptional Control' before coming to class.
• The animation will cover the factors that regulate eukaryotic gene transcription.

Chromatin Condensation Inactivating Gene Transcription

• Chromatin condensation inactivates gene transcription.

RNA Polymerases

• Eukaryotic cells have three RNA polymerases.
• RNA polymerase I synthesizes pre-rRNA.
• RNA polymerase II synthesizes mRNAs, some small nuclear RNAs (involved in mRNA splicing), microRNAs and siRNAs (regulate mRNA translation and stability).
• RNA polymerase III synthesizes tRNAs, 5S rRNA, and other small stable RNAs.

Eukaryotic RNA Polymerases Table

• A table details the RNA transcribed by each RNA polymerase and their functions.

Similarities of RNA Polymerases

• The crystal structure of yeast RNA polymerase II has been resolved at high resolution (Nobel Prize).
• All eukaryotic RNA polymerases are very homologous to yeast RNA polymerase II.
• A clamp domain in the polymerase (RPB1) accommodates DNA within the enzyme.
• RNA synthesis occurs in the catalytic center with Mg++.
• Synthesized RNA exits through a channel and is immediately capped by 7-methylguanosine.
• Bacterial RNA polymerase and eukaryotic RNA polymerase II have similar, recognizable structural components like beta, beta prime subunits (prokaryotic) and RPB1, RPB2 (eukaryotic); diagrams are provided.

RNA Polymerases Are Complex Molecular Machines

• The clamp and bridge, DNA position within the transcribing polymerase, RNA channel, and nascent RNA processing are important details.

RNA Polymerase II Contains a Unique Carboxyl-Terminal Domain

• RNA polymerase II has a unique carboxyl-terminal domain (CTD).
• The CTD is not shown in previous figures due to its lack of structure.

CTD Phosphorylation During Transcription

• CTD phosphorylation of RNA pol II is significant during transcription in vivo.

RNA Polymerase II Promoters and General Transcription Factors

• RNA pol II-transcribed genes are regulated by conserved basal promoter sequences (CORE PROMOTER SEQUENCES).

Core Promoter Sequences and Elements

• Core promoter elements include TATA box, initiator (Inr), BRE (TFIIB recognition element), and DPE (downstream promoter element).

Core Promoter Sequences and Recognition

• Transcription starts at the initiation site (typically an A on the coding strand).
• Four elements position the polymerase to specific promoters:
  • TATA box - a tight consensus sequence present in many highly transcribed genes
  • Initiator (Inr) - less conserved region
  • BRE (TFIIB Recognition Element) - influencing the activity of the promoter
  • DPE (Downstream Promoter Element) - influencing the activity of the promoter.

RNA Polymerases and Promoter Recognition

• RNA polymerases need general transcription factors (GTFs) to recognize and initiate transcription at specific positions. This complex is called the preinitiation complex.

General Transcription Factors

• General transcription factors (GTFs) (eukaryotic) are essential for RNA polymerase function, with different groups for RNA pol I, II, and III.

Future Lectures

• Lecture 4 will cover the interaction between promoter elements and basal transcription factors during recruitment and loading of RNA polymerases at promoters.
• Lecture 3 will focus on techniques to study these interactions.

This quiz explores the mechanisms and principles of gene control in multicellular eukaryotic organisms. It covers topics including transcription differences between eukaryotes and prokaryotes, chromatin regulation, and the roles of various transcription factors. Test your understanding of these crucial biological processes.