Hello everyone, I recently came across something very peculiar called internal ribosome entry sites (IRES). These secondary structures are present at the 5' end of many viral as well as mamallian mRNAs and are required for cap-independent translation (ex- at the time of apoptosis). Can somebody explain how the mRNAs are folded into such complex secondary structures? Are there any factors involved that regulate this folding or the mRNA itself catalyses this reaction?
It seems that many viral IRES will fold spontaneously into their 3-D structure without the need for proteins.
https://jvi.asm.org/content/77/11/6574
This results from base pairing of complementary sequences within the IRES.
Thanks @Adam B Shapiro, but there are various examples of cellular IRESes as well, which participate in both cap dependent and IRES mediated translation. What is stopping them from folding into IRES during cap dependent translation?
I don't know about this, but here is a review of the subject:
http://genesdev.cshlp.org/content/15/13/1593.full
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