Prokaryotic RNA Polymerase

Question 1

What are the substrates of prokaryotic RNA polymerase?

Answer 1

ATP, UTP, GTP, CTP

Question 2

Why is thymine used in DNA and uracil used in RNA?

Answer 2

Thymine is a methylated version of Uracil
* Methylation typically protects DNA from
enzymes which break-down DNA (nucleases)
* Uracil prefers to pair with adenine, but can
pair with other bases too
* Additional methyl group causes steric
hindrance in the DNA double helix to make
thymine only capable of pairing with adenine. This reduces the risk of mutation as mistakes in RNA do not get fed back into DNA.

Question 3

Label this diagram.

Answer 3

Question 4

What are the five subunits of the RNA polymerase core? Of the RNA polymerase holo enzyme?

Answer 4

Core: alpha + alpha + beta + beta’ + omega
Holo: core + sigma factor

Question 5

Label all parts of the RNA pol Core

Answer 5

Question 6

What do the two alpha subunits do in the RNA pol core in prokaryotes?

Answer 6

Recognizes promoter UP elements

Question 7

What does the beta subunit do in the RNA pol core in prokaryotes?

Answer 7

COntains polymerase activity

Question 8

What does the beta’ subunit do in the RNA pol core in prokaryotes?

Answer 8

Binds and holds on to DNA

Question 9

What does the omega subunit do in the RNA pol core in prokaryotes?

Answer 9

Enhances polymerase stability

Question 10

What do sigma factors do in prokaryotic transcription?

Answer 10

Recognize and assist RNA pol core to bind to specific promoters.

Question 11

What is the sigma factor we are most concerned with for prokaryotic transcription? Why

Answer 11

sigma 70 recognize -35 and -10

Question 12

Can RNA polymerase still transcribe without sigma factors?

Answer 12

Yes, but at a lower frequency and specificty.