The sequence of enzymatic reactions by which a 2,2,7-trimethylguanosine cap structure is added to the 5' end of an snRNA. The snRNA capping process includes the formation of 7-methyl-G caps found on all RNA polymerase II transcripts, followed by hypermethylation at the 2' position of the guanosine residue to convert a mono-methylated cap to a 2,2,7-trimethylguanosine cap structure. Note that the pol III transcribed U6 snRNA is also TMG capped.
snRNA 5\'-end processing