Lecture 23: RNA processing part II

Question 1

Alternative Splicing in Drosophila

Answer 1

Mechanism for the sex determination (XY Male) (XX Female)

Question 2

Sex-Lethal

Answer 2

Gene that is under transcriptional control and alternative splicing

-Only gets turned on in female in embryogenesis
- Later the late promoter is activated in male and female

Question 3

Alternative splicing sex lethal

Answer 3

Sxl protein binds to a splicing silencer upstream of exon 3 and for males sine there is a premature stop codon in Exon 3 the protein is truncated on non functional

Question 4

Sxl protein cascade

Answer 4

Regulates splicing of Tra so male does not have a functional transfer protein despite having a longer mRNA
dsx: Tra activates alternative splicing of the dsx protein by identifying the exon 4 5’
Polyadenylated Exon 4 recognizes promoters for female specific traits

Question 5

RNA Splicing and Genetic Disease

Answer 5

15% of single nucleotide mutations affect exon definition (alternative splicing)

Question 6

DMD

Answer 6

Mutation in X chromosome so commonly in males with small deletions from 47-50 causing frameshift and truncation

Question 7

DMD treatment

Answer 7

Eterlepsin Base pairs and blocks exon splicing enhancer at exon 51 restores partial gene function

Question 8

Exon splicing for DMD

Answer 8

Blocking splicing from 51 restores function because there is no longer a frameshift but will still lack the 47 48 49 50 and 51 exon (BLOCK ESE)

Question 9

RNA Editing

Answer 9

Enzyme in cytoplasm changes its sequence
Deamination A to I
or C to U

Question 10

Apolipoprotein B

Answer 10

Two isoforms caused by the deamination of C to U thus causing a premature stop codon of UAA

Question 11

Coupling of Polyadenylation and Export to Termination

Answer 11

Ser2 that recruits export factors

Question 12

Nuclear Pore Complexes

Answer 12

Openings in the nucleus that is highly ordered
It is huge
Molecules up to kDa can move through it

Question 13

NPC Transport Dependance

Answer 13

Dependance on hydrophobic protein interactions (reversible)

Question 14

Protein import by NPC

Answer 14

Protein synthesis in cytoplasm and imported because proteins have a NLS

Question 15

Nuclear Transport Receptors

Answer 15

Importunes bind to NLS domain and associate to FG repeats on nucleoporins

Question 16

Ran

Answer 16

protein that exists in two conformations (GTP or GDP)
GEF in nucleus converts RanGDP to GTP and binds inportin then moves back to cytoplasm. Then GAP hydrolyzes RanGTP to GDP then sequence repeats

Question 17

Exportin

Answer 17

(NES)

Exportin/cargo/ranGTP move to cytoplasm then GAP dissasociates protein complex

Question 18

RNA transporter

Answer 18

NXF1 and NXT1 recognize SR proteins and form a domain that interacts with the FG repeats in nucleoporins

Question 19

When RNA exported to cytoplasm

Answer 19

All nuclear proteins must be kicked off imported in the nucleus and the cytoplasmic proteins are added instead.

Question 20

Npl3

Answer 20

SR protein

Question 21

Glc7

Answer 21

phosphatase

Question 22

Function of Npl3

Answer 22

it becomes dephosphorylated and promotes binding of NFX1 and NXT1 exporter

Question 23

Sky1

Answer 23

kinase that phosphorylates NpI3 for recycling