RNA Metabolism

Question 1

RNA has an extra OH where?

Answer 1

2’C

Question 2

Is a primer needed for RNA synthesis?

Answer 2

No

Question 3

Purines are which nucleotides?

Answer 3

A & G

Question 4

Pyrimidines are which nucleotides?

Answer 4

T & C

Question 5

Sigma cycle occurs in what type of organisms?

Answer 5

Prokaryotes

Question 6

What is sigma replaced with in the transcription cycle?

Answer 6

NusA protein

Question 7

When is the sigma subunit released?

Answer 7

as soon as elongation begins

Question 8

What does RNA pol I synthesize?

Answer 8

Pre-rRNA

Question 9

What does RNA pol II synthesize?

Answer 9

mRNA, specialized RNA

Question 10

What does RNA pol III synthesize?

Answer 10

tRNA, 5sRNA, specialized RNA

Question 11

Describe the assembly of the transcription complex in eukaryotes

Answer 11

1. TBP binds to TATA
2. TFIIA and TFIIB bind to stabilizes TBP and DNA
3. TFIIF and pol II come to bind
4. TFIIF targets pol II to promoters
5. TFIIE and TFIIH bind = closed complex

Question 12

Describe initiation of transcription in eukaryotes

Answer 12

1. TFIIH has helicase activity-creates transcription bubble

2. CTD is phosphorylated-pol complex escapes promoter

Question 13

Describe termination of transcription in eukaryotes

Answer 13

1. Elongation factors dissociate
2. CTD is dephosphorylated
3. Termination facilitated by termination factors

Question 14

What is the CTD?

Answer 14

Carboxy terminal domain, contains heptad AA repeats (52 in humans)

Question 15

Describe the process of 5’ capping

Answer 15

Occurs after 20-30bp
condensation of GTP w triphosphate at 5’ carried out by enzymes on CTD
Cap remains bound to CTD using cap binding complex (CBC)

Question 16

Which classes of introns are capable of self splicing?

Answer 16

1 and 2

Question 17

Which introns use splicing by splicosome?

Answer 17

3 & 4

Question 18

What are the 5 snRNPs?

Answer 18

U1 U2 U3 U5 U6

Question 19

How to snRNPs work?

Answer 19

form lariat, release intron

Question 20

Does building the poly A tail require ATP?

Answer 20

yes

Question 21

What is the cleavage signal for poly A tail?

Answer 21

AAUAAA

Question 22

How is the poly A tail formed?

Answer 22

1. Cleavage seq on RNA bound by endonuclease bound by CTD
2. RNA is cleaved at 10-30 bp past AAUAAA
3. Polyadenylate polymerase synthesizes a poly A tail 80-250 bp long

Question 23

What is the function of the Poly A tail?

Answer 23

Binding site for proteins, helps protect mRNA from enzymatic destruction.

Question 24

5’-5’ triphosphate linkage occurs where?

Answer 24

In 5’ RNA capping, between 5’ terminal residue and 7 methyl guanosine

Question 25

Where is the CTD?

Answer 25

on RNA pol2