Post transcriptional control II

Question 1

Name three types of RNA editing

Answer 1

Base insertion
Cytosine to uracil
Adenine to inosine

Question 2

How do base insertions work?

Answer 2

Guide RNA molecules find complementary regions.

They donate U’s from poly U tail to the mismatched regions.

Question 3

Explain how cytosine -> uracil

Answer 3

Via deamination

Usually involves a factor to anchor editing zone in place so is highly specific.

Question 4

Explain how adenine -> inosine

Answer 4

Via deamination

Question 5

What are ribozymes and what do they do?

Answer 5

Small molecules with catalytic activities.
There are complementary base pairs between ribozyme and substrate
Substrate is cleaved
Product is release (cleaved RNA)

Question 6

How is rRNA processed?

Answer 6

Mature mRNA transcript is heavily coated in proteins which are useful for transport out of nucleus pore complex, which only lets macromolecules through unless they have a ‘ticket’ signal.

Question 7

What does miRNA do?

Answer 7

Small single stranded non coding sections of RNA that can regulate eukaryotic expression.

Question 8

How are miRNA’s processed?

Answer 8

In the nucleus a Drisha-DGCR8 cleaves the ‘legs’ off pri-miRNA.
It then leaves nucleus, the loop is cleaved by Dicer.
Dicer then pairs up with Argonaute forming RISC.
RISC blocks the translation.