9: How does bacterial transcription start

Question 1

What are some examples of antibiotics that specifically inhibit transcription? (3)

Answer 1

• Rifamycin
• Cordycepin
• Actinomycin

Question 2

How does Rifamycin prevent transcription

Answer 2

• It is bacteria specific

- It inhibits after a few nucleotides synthesised

Question 3

How does cordycepin prevent transcription?

Answer 3

• Adenosine analog

- Blocks elongation

Question 4

How does actinomycin D prevent transcription?

Answer 4

-Inserts between pairs of GC bases in DNA to prevent transcription

Question 5

Describe the promoter region

Answer 5

• Where RNA polymerases binds
• The alpha helices of the sigma factor bind to the DNA major groove
• Sigma factor is a protein subunit of the RNA polymerase
• There are alternative types of sigma factor

(slides)

Question 6

Describe alternative sigma factors

Answer 6

• They are active under different conditions and recognise different promoter sequences
• They coordinated distantly located operons
  (slides)

Question 7

Describe the details of RNA

Answer 7

• Beta subunits are catalytic
• Sigma(s) provide specific binding to DNA
• Similar overall structure to other RNA polymerases but there are differences such as having antibiotic targets
• DNA dependent RNA polymerase (RNAP, RNA pol) binds to a promoter in the DNA