Hi all,
I know that acetylation relaxes chromatin wrapped about histones to allow for greater transcription but is the function of acetylation on the N terminus of proteins known? It should have been co-transcriptional modification my bad.
El Curandero
Which proteins, histones? Didn't you just say the function? Also, why are you talking about the N-terminus? Side chains are modified. Never really heard of any notable N-terminus modifications, myself.
Methylation can either activate/repress transcription, depending on the specific lys/arg residue that is methylated/how much methylation occurs. Might be good to know what happens with H3K4, H3K9, H3K36, H3K79.
^Sorry, misread your post there (although going to leave this just in case histone methylation is what you meant).
The biggest instance of post-transcriptional methylation I can think of is the 5' cap structure. After the 5'-5' triphosphate linkage, the N7 of guanosine is methylated, the 2' O(H) of the second nt (after the guanosine cap) is methylated, and sometimes the 2' O(H) of the third nt is methylated as well. I'm not sure if this suffices for what you are asking about. Let me know.
As an aside, I'm not sure if they call what you're referring to co-transcriptional modification. You're talking about histone modifications. Co-transcriptional modifications are things like 5' capping and splicing, which happen
while the transcript is being made (hence
co-transcriptional modification). Poly A tail then comes once the transcript is finished. I do, however, see how histone modifications could occur in tandem with transcription (i.e. something was being transcribed and all of a sudden a methylation occurs on the histone tail, causing immediate repression), but I don't think histone modifications are grouped that way -- because it could be either or. Probably, histone modifications happen very often
before transcription, because those modifications are working to
activate transcription in the first place. This is why you couldn't specifically call histone modifications co-transcriptional modifications - at least I think.
