POST TRANSLATIONAL PROCESSING II

Question 1

What is RNA editing?

What seq is usually changed?

Answer 1

A point change in RNA seq.

Cytosine - Uridine

Adenosine - Inosine

Question 2

What are the factors req for mRNA transport?

Answer 2

Cap, PolyA tail, hnRNP proteins, RNA processing (particularly the 3’ end processing)

Question 3

Is transportation undirectional or multi-directional?

Answer 3

Unidirectional

Question 4

What is the function of hnRNP?

Answer 4

It allows the unidirectionality of mRNA transport by binding to mRNA and facilitates its transport into the cytoplasm and once in the cytoplasm, it disconnects thereby preventing the mRNA going back

Question 5

Can the transport step regulate gene expression? Why and why not?

Answer 5

Yes, it can.

It the synthesized mRNA is not transported to the cytoplasm, there can not be a gene expression.

Question 6

What are the types of RNA decay?

Answer 6

1) Degradation from 3’ end (removal of the polyA tail)
2) Degradation from 5’ end (does not depend on removing polyA tail)
3) Endonuclease-mediated (cut within the molecule and degradation in the middle)

Question 7

What are the factors that can affect stability?

Answer 7

AU-rich regions in the 3’ end as well as factors binding the RNA

Question 8

What is the importance of intron/exons

Answer 8

Genetic diversity

Some introns have additional functions in RNA metabolism

Question 9

True / False

About 10% of human genes are naturally intronless

Answer 9

True

Question 10

List the contributions of intron/splicing

Answer 10

3’ end processing

nuclear mRNA stability

mRNA transport

mRNA capping

Some cases transcription

Question 11

Name some naturally intronless genes and what they do

Answer 11

Herpes simplex virus thymidine kinase (TK)

Human c-JUN gene

Histone genes

They contain seq that mimic the effects of introns, allowing for mRNA accumulation and gene expression in the absence of introns and splicing

Question 12

What are the factors that contributes to RNA instability?

Answer 12

AU-rich seq in the 3’ UTR

Factors binding RNA

Question 13

What is the difference btw intro-dependent and naturally intronless mRNAs?

Answer 13

Intro-dependent mRNAs are genes that absolutely need introns for there to be mRNA accumulation and gene expression

Naturally intronless mRNAs are genes that contain seq that can mimic the effects of introns. They are used to rescue mRNA genes w/out introns.

Question 14

What are the considerations that must be observed when inserting naturally intronless gene for beta-globin?

Answer 14

1) It must be inserted at the UTR seq
2) Must be at the 5’ UTR for optimal accumulation

Question 15

What is the strong evidence for co-transcriptional RNA processing?

Answer 15

The insertion of naturally intronless gene (TK) at the 5’ UTR

Question 16

Why must TK seq be at the 5’ end?

Answer 16

Because…

RNA processing is co-transcriptional and directional (5’ - 3’). Therefore, TK should be inserted at the begining (where it is stabilized) because inserting at the end (3’ end) would result in the degradation of the gene even before it reaches the end

Question 17

Why is RNA polymerase critical to integrating transcription and splicing?

Answer 17

It contains a domain that can assoc with processing factors which allows for co-transcriptional processing.

Question 18

siRNA is used for what?

Answer 18

Targets mRNA for degradation

Question 19

What is the name of the factor used to create siRNA?

Answer 19

Dicer

Question 20

siRNA works with a complex and an assoc, what are they

Answer 20

RISC complex and Argonaute

Question 21

The siRNA, RISC and Argonaute complex can be used in two ways

Answer 21

Naturally to degrade viruses and experimentally to downregulate gene expression.

Question 22

Why is Endo-siRNA an exception to the rule?

Answer 22

It is produced from endofenous RNA

Question 23

What are Ribozymes?

Answer 23

RNA emzymes that can catalyze reactions on their own w/out protein

Question 24

Ribozymes are found where?

Answer 24

In cells that sunthesize proteins

Question 25

What can be used as an alternative to siRNA and how?

Answer 25

Ribozymes. They can be designed to specifically target and cleave RNAs to knockdown gene expression