Eukaryotic Transcription

Question 1

What are the two main differences between eukaryotic and prokaryotic transcription?

Answer 1

1. Genes in prokaryotes are all transcried by a single polymerase, whereas in eukaryotes there are three types of polymerase (I, II, and III)
2. Eukaryotic RNA polymerases need to interact with a variety of additional proteins to initiate transcription, whereas in prokaryotes the polymerase binds directly to promoter sequences

Question 2

Prokaryotes contain a single RNA polymerase holoenzyme, whereas eukaryotes contain three RNA polymerases that transcribe different sets of genes. What RNAs are synthesised from each eukaryotic RNA polymerase?

Answer 2

Prokaryotes contain a single RNA polymerase holoenzyme, whereas eukaryotes contain three RNA polymerases that transcribe different sets of genes.

Question 3

RNA Poll II consists of __ subunits and cannot initiate transcription without __________ ________. The largest subunit of Pol II has a ________-________ ______ (___), which consists of multiple repeats of 7 amino acids.

The general _____________ ________ are important for initiation by Pol II at all promoters; they are identified as ___{_}_.

Answer 3

RNA Poll II consists of 12 subunits and cannot initiate transcription without transcription factors. The largest subunit of Pol II has a carboxy-terminal domain (CTD), which consists of multiple repeats of 7 amino acids.

The general transcription factors are important for initiation by Pol II at all promoters; they are identified as TF_NX.

Question 4

How many subunits does RNA Polymerase II have?

Answer 4

12

Question 5

What is a cis-acting element? What is an exapmle?

Answer 5

A region of DNA or RNA that regulates the expression of genes located on that same molecule of DNA.

e.g. TFIIB recognition element (BRE box), TATA box, Initiatior box (Inr), downstream promoter elements (DCE, DPE, MTE)

Question 6

What are the main types of regulatory elements? What do they do? [4]

Answer 6

1. General transcription factors: respond to co-activators, position RNA polymerase at the start of the gene, and then releases it to transcribe the mRNA
2. Co-activators: transmit signals from the activators to the basal factors (e.g. GTFs)
3. Activators: bind DNA at enhancers, interacts with the transcription complex to increase the rate of trancription
4. Represssors: bind to ‘silencer’ sites of DNA, prevents the binding of activators to nearby enhancers to slow transcription

Question 7

Which 6 general transcription factors are needed by RNA Pol II in order to initiate transcription? List them in order.

Answer 7

1. TFFIID (+TBP)
2. TFIIA
3. TFIIB
4. TFIIF
5. TFIIE
6. TFIIH

DABFEH!

Question 8

What are the roles of the general transcription factors for RNA Poll II?

Answer 8