[annotation] RNA trimethylguanosine cap binding query

[Harold Drabkin]

Valerie Wood wrote:
> I recently used the term RNA trimethylguanosine cap binding  to 
> annotate pombe telomerase RNA and represent the fact that this is 
> trimethylguanosine capped, but on re-reading the definition  I'm not 
> sure if this is correct?
> Can I use this for the modification itself?  or is it for gene 
> products which interact with a capped product?
It represents some gene product that binds to the triMeG cap present on 
an mRNA. Not the gene product that makes the cap. A binding term should 
never be used for a covalent bond. Binding implies a reversible reaction 
at STP, with a Ka and Kd.

GPI anchor binding it meant to be used for something that binds the the 
GPI anchor and not covalently linked to it.

>
> There do not appear to be any other annotations to this term despite  
> the fact that many RNAs are capped which is another reason which made 
> me suspect my usage may be wrong.
>
> Should  the binding terms should only be used for non-covalent 
> modifications (although this is only in some of the binding defs?), 
> and  does not represent the use of some terms. For instance GPI anchor 
> binding is used for a number of proteins which are GPI anchored, in 
> addition to proteins which bins the GPI moiety during GPI anchor 
> biosynthesis.
>
> Cheers
>
> Val
>
> Def:
> Interacting selectively with the trimethylguanosine (m(3)(2,2,7)-GTP) 
> moiety located at the 5' end of some RNA molecules. Such trimethylated 
> cap structures, generally produced by posttranscriptional modification 
> of a 7-methylguanosine cap, are often found on snRNAs and snoRNAs 
> transcribed by RNA polymerase II, but have also be found on snRNAs 
> transcribed by RNA polymerase III. They have also been found on a 
> subset of the mRNA population in some species, e.g. C. elegans.
>
>