B2.072 Prework 2 Functional Outcomes of mRNA Splicing

Question 1

splice signal sequence ambiguity

Answer 1

strong- match consensus sequence well

weaker- variation from consensus sequence

Question 2

SR and hnRNP

Answer 2

RNA binding proteins that regulate splicing

Question 3

how does diversity of mRNA/protein arise

Answer 3

utilization of both alternative splicing and termination/polyadenylation

Question 4

what are some function outcomes of splice variants

Answer 4

altered activity or regulation of proteins produced (mild change to complete opposite activity)
altered stability or translation of mRNA
-loss of destabilizing elements from mRNA
-loss of miRNA target sites from mRNA

Question 5

what is an example of alternative splicing changing protein function drastically

Answer 5

glucocorticoid receptor
active protein (9a)- dimerizes, activates transcription of target gene
suppressor (9b)- binds 9a form and prevents transcriptional activation
mutually exclusive

Question 6

what is an example of 2 splice isoforms having different properties

Answer 6

2 isoforms of pyruvate kinase
PKM1- non regulated
PKM2 - allosterically regulated (negatively by ATP and positively by FBP)

Question 7

how is the production of PKM2 regulated?

Answer 7

in proliferating cells: high level of specific RNA binding proteins influences use of exon 10 instead of 9 in PKM1
RNA binding proteins: PTB1 and nhRNPA

Question 8

how is the production of PKM1 regulated?

Answer 8

in most cells, there are low levels of specific RNA binding proteins
exon 9 is the default isoform

Question 9

discuss splicing and its influence on cancer

Answer 9

alternative splicing events occur in high number of tumors
deregulation of specific splicing regulatory proteins account for altered splicing
“hallmark” - shift of proteins from most common isoform to alternative

Question 10

outcome of intron retention

Answer 10

frameshift, loss of mRNA via nonsense-mediated decay (NMD)
no protein produced
(hits a premature stop codon in intron)