Eukaryotic Transcription (Lec8)

Question 1

Eukaryotic RNA Polymerase

Answer 1

large
certain subunits are shared
polymerase-specific subunits defines specific functions

RNA Pol I, II, III

Question 2

RNA Polymerase I

• location
• genes

Answer 2

location: Nucleolus

Ribosomal genes

Question 3

RNA Polymerase II
location
genes

Answer 3

Nucleoplasm

all other genes

• heterogeneous nuclear RNA (hnRNA)
• spliced = mature mRNA
• small nuclear RNA (snRNA)

Question 4

RNA Polymerase III

• location
• genes

Answer 4

nucleoplasm

• small RNA
• 5S rRNA
• tRNA

Question 5

Promoters

Answer 5

Conserved sequences
cis-elements

recognized by RNA polymerase and/or Transcription factors (TFs)

Question 6

Euk vs Prok

Euk - initition and mode of regulation

Answer 6

Inititation
- euk promoters involves a large number of transcription factors that bind at cis-elements

Common mode of regulation of euk genes
- positive

Question 7

Eukaryotic Promoters

-RNA Polymerases I, II, III

Answer 7

RNA polymerase I and III

• restricted set of promoters
  
  • can be downstream - within ORF
• small number of accessory protein factors (TFs)

RNA Polymerase II

• diverse in sequence composition
• modular in design - various domains
• recognized by multiple transcription factors
• some Tfs common bind to many promoters
• others very specific for certain classes of genes

Question 8

RNA Pol II Transcription factors

Answer 8

Basal Factors

• initiate RNA synthesis at all promoters
• determines initiation site
• forms complex with RNA pol ii at start point

Upstream Factors

• specific binding elements
• recognize specific short consensus elements upstream of start point
• not regulated
• increases initiation efficiency

Inducible Factors

• binds to response elements
• similar to upstream factors BUT regulatory role
• regulates transcription patterns
• synthesized/ activated at specific time or in specific tissues

Question 9

Eukaryotic Transcription Process

Answer 9

Notes

Question 10

Eukaryote
Transcription Initiation (ELEMENT)
- stimulate initiation and influence promoters

Answer 10

Enhancer elements 
- up or down stream
tissues specific / regulation 
- stimulate (enhances) transcription initiation
- can function in either orientation 

• only influence promoters when present on the same DNA duplex

Question 11

Eukaryote: TATA Box

Answer 11

RNA Pol I initiation

- similar to -10 bp in prok but at -25 bp

Question 12

RNA Polymerase III ( Initiation and termination)

Answer 12

INITIATION ______________________________
Promoters
1. 5S and tRNA promoters
- internal within gene

2. snRNA promoters
   - Upstream
   - contain
   * TATA site
   * PSE (Proximal sequence element) site
   * Oct site

*some snRNA are transcriped by RNA Pol II (2)

• initiation occurs at TATA site
• bindingof factors at PSE and Oct sites = enhances transcription - TBP also involved in this complex (TB-TATA Box complex)

Transcription Factors

1. TFIIIA and TFIIIC
   - help positioning RNA Pol III
2. TFIIIB
   - essential for trabcscription
   * together with TBP (TATA binidng proteins)

Termination ______________________________
Discrete sites
- U sequence embedded in GC rich region
- similar to Rho-independent termination

Question 13

RNA Polymerase II (2) \

• INITIATION
• TERMINATION

Answer 13

Initiation_________________________________

several TFs involved
basal Tfs associate with RNA Pol II to form basal transcription apparatus

Promoters
- TATA box (-25)

larger subunits contains carboxy-terminal domain (CTD)
- phosphorylation tales place via TFIIH kinase activity = release RNA pol II from initiation complex
= allows transcription to elongate