TXN II: RNA Processing

Question 1

3 Steps of RNA Processing

Answer 1

1. Capping (cotranscriptionally) and polyadenylation

3. Splicing

Question 2

mRNA Capping

Answer 2

5’ to 5’ TRIphosphate bond. methyl cap marks RNA

• gives stability
• directs to cytoplasm
• required for translation
• marks as nonviral

Question 3

Cleavage and Polyadenylation

Answer 3

AAUAAA marks for cleavage
Poly (a) polymerase poops out long chain of A residues (no template needed)
This:
-marks mRNA as special
-speeds up translation
-stabilizes

Question 4

Protein Diversity and Polyadenylation?

Answer 4

Variations on where transcribed RNA is polyadenylated = different translation (different proteins)

Question 5

Spinal Muscular Atrophy

Answer 5

Motor Neuron degeneration. caused by mutation in SMN1 protein that inhibits snRNP assembly by splicing defects

Question 6

snRNP in RNA splicing

Answer 6

Recognize Splicing Signals (conserved nucleotide sequence) and holds RNA in place while splicing occurs, catalyzing the process

If there are insufficient numbers of snRNPs inefficient/incorrect splicing occurs which results in different proteins. This equals different function.

Question 7

Lariat Structure

Answer 7

1. snRNP + branchpoint A form complex U2 which binds with 5’ G of INTRON + snRNP (complex U1).
2. 3’-G at end of EXON 1 attacks 5’G of EXON 2
3. Introns become lariat to be degraded while exons condensed. This is catalyzed by snRNPs U3 4 5

Question 8

Splice Variants

Answer 8

variants in proteins caused by variants in splicing can create crappy function. Associated with SNP.

Question 9

Auxillary Splicing Regulatory Elements

Answer 9

bind to places within intron/exon to promote or repress choice of splice site

Question 10

Beta-Thalassemia

Answer 10

Reduced beta globin

Caused by abnormal splicing because of mutation in normal splicing acceptor site and binds to cryptic splice site

B0 mutation:

• exon 2 binds to cryptic site on intron instead of normal acceptor site on exon3
• severe

1 B+:

• Not as severe
• exon 1 sometimes binds to cryptic site btwn. ex1 and ex2 but sometimes binds to acceptor site on ex2

1 B Hb E:
-new donor site in ex1