lecture 10 recap Flashcards
if we lose cap or polyA tail mRNA wont be
circular
bulk of mRNA is degraded by
exonucleases
decapping enzymes give an end for the exonucleases to access e.g.
DCP1 and DCP2
deadenylases e.g. Ccr/Not complex remove what
polyA tail
endonucleases cut the mRNA in the
middle e.g. argonaute, Swt1 and Smg6
the exosome works from
3’ to 5’
XRN1 works from
5’ to 3’
when polyA gets to short it is signalled for
degradation
signals for premature degradation
AU rich elements in 3’ UTR
nonsense codon
c-fos major coding determinant
miRNA
deadenylation independent decay:
1. rps28B binds to mRNA and it recruits what
Edc3 which promoted decapping
- endonucleases cut mRNA in the middle allows exosome or XRN1 to degrade without removing
cap or poly a tail
NMD =
nonsense mediated decay
how can the cell recognise if the stop codon is in the right place
due to the distance bwteen it and the splice site
if the distance is greater than __ nuceltides then its an NMD target
55
what are exon junction complexes
proteins deposited onto the exons after splicing
they remain on the mRNA until the the first round of translation when they are removed by what
the ribosome
if its a premature stop codon EJCs will remain downstream which proteins from the EJC are then recruited
UPF proteins and they interact with the RNA degradation
RNAi =
RNA interference
siRNA
small inhibitory RNA
miRNA
micro RNA
RISC
RNA induced silencing complex
si RNA and miRNA are how long
21-23 nucleotides
siRNA are complimentary to the
target RNA
miRNA are
imperfectly complementayr to a
traget DNA
si RNA leads to
degradation
miRNA leads to block in
translation
drosha and dicer do what
cute the pre miRNA into miRNA
ds RNA is cut by dicer to
siRNA
they cur RNA is then
unwound into single strands
siRNA bind to
argonaute
argonaute is the
nuclease
miRNA binds to the mRNA in the
3’ UTR and blocks translation
3’ UTR length changes
longer 3’ UTR =
more regulation
what cells have shorter 3’ utr
proliferating cells
what cells have longer 3’ utr
embryonic development cells as cells get differentiated and things slow down so need more regulation
