Mutations Flashcards
What do SMN1 mutations cause and how can this be treated?
cause spinal muscular atrophy; alternative splicing resulting in splicing out of the mutation-containing exon (exon 7)
what is caused by abnormal splicing of CD44?
tumor metastasis (fun fact: splice variants can be used as diagnostic and prognostic markers)
APC mutations cause (and, what is APC)
colon cancer; transcriptional regulatory protein
pRB mutations cause (what is pRB)
retinoblastoma and small cell lung cancer; transcriptional regulatory protein; inhibits cell cycle, and is inactivated by CDK phosphorylation (and cell can divide)
XP-B and XP-D mutations cause (and what are these proteins)
Cockayne’s syndrome, xeroderma pigmentosum, trichothiodystrophy; they are both subunits of TF2H and are transcriptional regulatory proteins. Specifically, XP-B opens the DNA at the promoter to permit initiation of transcription
p53 mutations cause
most cancers; p53 is a transcriptional regulatory protein
c-myc mutations cause
Burkitt’s lymphoma; c-myc is a transcriptional regulatory protein
RAR mutations cause
acute promyelocytic leukaemia; RAR is a transcriptional regulatory protein
SRY mutations cause
sex reversal; SRY is a transcriptional regulatory protein
PIT-1 mutations cause
dwarfism; PIT-1 is a transcriptional regulatory protein
XH-2 mutations cause
ATR-X (X-linked mental retardation); XH-2 is a transcriptional regulatory protein
What happens if there is decreased phosphorylation of E1F-4E?
does not bind the G-cap in the cytoplasm as tightly, resulting in overall decrease of cellular translation
Which snRNA recognizes the 5’ splice site (and what is the signal?)
U1 snRNA; signal is GU
Which snRNA recognizes the A-branch point?
U2 snRNA
What is the signal for the 3’ splice site, and what protein binds it?
AG; U2AF (U2 associated factor)
Explain the 2 biochemical steps of splicing
- the 2’ OH of the A at the branch point attacks the 5’ splice site phosphate
- The 3’ OH of exon 1 attacks the 5’ phosphate at the 3’ splice site.
What are the 2 enzymatic steps of 3’ polyA tail addition
- cleavage of 3’ OH
2. polyadenylation by hydrolysis of ATP –> AMP + PPi
What is one example of the result of alternative polyA site choice?
membrane bound (B cells) vs. secreted (plasma cells) forms of IgM
What is the polyA site consensus sequence?
AAUAAA
The polyA site consensus sequence is usually how many nucleotides upstream from the 3’ terminal polyA tract?
11-30
A single nucleotide change in the polyA site consensus sequence can cause which disease? (And what is the change?)
Alpha-thalassaemia (AATAAG instead of AATAAA)
What is one hypothesis for how alternative cleavage and polyadenylation activate oncogenes in cancer cells?
Shortening of the 3’ UTR may provide fewer target sequences for regulation of mRNA degradation by miRNA
What is the function of snRNA
splicing, located in the nucleus
What is the function of snoRNA
maturation of rRNA (forms ribosome), located in the nucleolus
what is the function of telomerase RNA?
template for telomere synthesis
What is the length of miRNAs, what is the precursor and what are some of their functions?
about 21 nucleotides long; derived from hairpin precursor; they bind to sites on the 3’ UTR of mRNA; an imperfect match results in degradation of mRNA OR repression of translation; a perfect match results in degradation of mRNA; they can also target the coding region or the 5’ UTR
What is the length of siRNAs, what is the precursor and what are some of their functions?
about 22 nucleotides long; derived from long double-stranded RNA; perfect match; target transposon or virus (mRNA degradation, transposon degradation, chromatin formation, transcriptional silencing)