Kozak and IRES sequnces same thing?

gj at nospampobox4.stanford.edu gj at nospampobox4.stanford.edu
Fri Nov 7 16:45:27 EST 1997


John Smith wrote:
> 
> gj at nospampobox4.stanford.edu wrote:
> 
> > Hi, I work on IRESes the major difference between kozak consensus, i.e.
> > cap-dependent initiation, and an IRES, i.e. cap independent initiation
> > is that the former required eif4e and a cap while cap independent
> > initiaion does require either.
> 
> This may not be entirely true.  While it is clear that cap-independent
> initiation of translation does occur in picornavirus infected cells, which
> inactivate the p220 component of eIF4E, that does not mean that the
> components themselves play no role in the initiation event.
> 
> > Interesting IRES mediated initiation
> > requires all the other initatiation factors.  they cannot substitute for
> > one another as a previous poster states kozak sequence is the sequence
> > around the AUG while an IRES is more like a cap.
> >
Hi , this is gregg from peters lab. Yea you are right but you mean eif4f
not eif4e which is the cap binding  protein. eIF4F refers to the
cap-binding complex. unless I am confused I don' want to go check right
now. The idea is that when p220 is cleaved the eif4e binding site which
is N-ternm on eIF4G is seperated from the eif3 and 4A binding sites
which are c-term on eif4G.  This allows the c-term of
eif4G(p220)associated with eif3 and eif4a to associate with the IRES and
recruit the ribosome. Funny running into you here. Hope things are
well.  

OTher IRES containing cellular RNA's of the top of my head are eif4G 
and basic fibroblast growth factor mRNAs. Among others I think to dat
there ar e 6 IRES containing cellular RNAs all but one(antennapedia) are
from mammalian cells. I don't have the references handy bu there are
several good reviews out. If 
JD want's more info let me know.   Gregg   email no good



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