RNA Polymerases - Lecture 10

Question 1

What makes up the prokaryotic RNA polymerase?

Answer 1

○ Sigma (σ)
○ 2 x alpha (α)
○ 2 x beta (β + β’)
○ Omega (ω)

Question 2

What is the sigma unit responsible for?

Answer 2

Recognises the promoter

Question 3

What are the alpha units responsible for?

Answer 3

Activation of the polymerase and to work under certain conditions and assembly

Question 4

What are the beta units responsible for?

Answer 4

○ Catalysis
○ Termination
○ Open up DNA and make RNA copy

Question 5

What is the omega unit responsible for?

Answer 5

○ Assembly
○ Folding
○ Required for some genes
○ Doesn’t do much

Question 6

What happens when the RNA polymerase begins transcribing?

Answer 6

○ Sigma unit is ejected
○ Core enzyme is competent for elongation

Question 7

How many RNA polymerases do prokaryotes have?

Answer 7

One

Question 8

What are the RNA polymerases that eukaryotes have?

Answer 8

○ Pol I
○ Pol II
○ Pol III

Question 9

What does the Pol I transcribe?

Answer 9

Ribosomal RNA genes (rRNA)

Question 10

What does Pol II transcribe?

Answer 10

○ Protein coding genes (mRNA)
○ Small Nuclear RNA (snRNA)
○ Needs accessory proteins to bind to DNA

Question 11

What does Pol III transcribe?

Answer 11

○ transfer RNA (tRNA)
○ rRNA
○ snRNA

Question 12

What transcription factors are involved in the assembly of RNA polymerase II?

Answer 12

○ TFIID
○ TFIIA
○ TFIIB

Question 13

What is TFIID?

Answer 13

○ Transcription factor 2
○ Made up of TATA binding proteins (TBP): recognise A-T rich sequences and has a sequence similar to σ
○ Also made up of TBP-Associated Factors (TAFs)

Question 14

What is TFIIA?

Answer 14

Helps TFIID to bind

Question 15

What is TFIIB?

Answer 15

Sets distance from TATA element to start site

Question 16

What does TFIIE, F, H, J, K do?

Answer 16

○ Interacts with DAB complex and recruitment of polymerase II
○ Blocks non-specific binding of polymerase II to DNA
○ Promoter clearance
○ Helicase
○ Processivity and elongation
○ Transcription-coupled DNA repair

Question 17

How is RNA polymerase I recruited?

Answer 17

○ Upstream control element (UCE) is binded to upstream binding factor (UBF)
○ UBF binds to SL1
○ SL1 recruits RNA pol I

Question 18

What makes up SL1?

Answer 18

○ TBP
○ Pol-I specific TAFs

Question 19

How is RNA polymerase III recruited?

Answer 19

○ Promoter is withing coding region
○ Regulatory regions are after transcription start site (A box and B box)
○ TFIIIC binds to B box
○ TFIIIB is recruited upstream of start-site
○ Once transcription is initiated, TFIIIC gets displaced

Question 20

What makes up TFIIIB?

Answer 20

TBP + 2 pol III specific TAFs

Question 21

What is different about RNA polymerase III when transcribing 5S rRNA genes?

Answer 21

Use an extra factor TFIIIA to recruit TFIIIC

Question 22

What is different about RNA polymerase III when transcribing snRNA genes?

Answer 22

○ Upstream promoter
○ TATA box recognised by TBP