RNA Processing

Question 1

List the 5 types of RNA modification.

Answer 1

cleavage
splicing (removal of intron via cleavage and rejoining)
5' capping
polyadenylation
editing

Question 2

Name the three types of RNA editing.

Answer 2

base insertion
base deletion
base modification

Question 3

Functions of 5’ cap (4)

Answer 3

~ protection from degradation
~ translatability - cap stimulates translation
~ transport from nucleus to cytoplasm
~ stabilises the mRNA

Question 4

Capping

Answer 4

addition of a cap structure at 5’ end of eukaryotic mRNA

~ unusual 5’ to 5’ triphosphate link

Question 5

Polyadenylation

Answer 5

addition of a 3’-polyadenosine tail of ~200As by enzyme poly(A)polymerase

Question 6

Splicing

Answer 6

removal of introns to produce mature mRNA which can be used as a template for transcription
~ done by transesterification reactions
~ removed using a spliceosome or via self-splicing

Question 7

Spliceosome

Answer 7

~ made up of snRNPs, proteins and snRNA

~ carries out slicing (transesterification reactions) on precursor mRNA

Question 8

Lariat strutcure

Answer 8

bit like a lasso, circular

Question 9

snRNP

Answer 9

small nuclear ribonucleoproteins

~ each has its own function

Question 10

EJC complex

Answer 10

exon junction complex

~ left at splice junctions after splicing

Question 11

RNA editing

Answer 11

process that adds/delectes bases from pre-mRNA or chemically alters bases resulting in an mRNA with bases that doesn’t match the DNA sequence

Question 12

Trypanosomes

Answer 12

~ causes sleeping sickness
~ Tetsy fly = vector
~ only organism know to do RNA editing

Question 13

How is capping, slicing and polyadenylation coordinated?

Answer 13

by RNA pol II

Question 14

RNA degradation in eukaryotes

Answer 14

removal of poly(A) tail directed by AU rich elements as reduces stability

Question 15

RNAi

Answer 15

involved with mRNA degradation and down regulate mRNA levels

~ two types: siRNAs and miRNAs

Question 16

siRNA

Answer 16

~ derived from processing longer dsRNA

~ recruits siRISC

Question 17

miRNA

Answer 17

~ derived from RNA pol II transcripts

~ recruits miRISC

Question 18

siRISC

Answer 18

basepairs with mRNA causing Ago to cleave the target mRNA

~ artificial siRISC used as a tool in cell biology

Question 19

miRISC

Answer 19

binds to 3’ end of mRNA and prevents translation

Question 20

RISC

Answer 20

RNA-induced signalling complex