part of RNA methyltransferase activity S-adenosylmethionine-dependent methyltransferase activity 7-methylguanosine cap hypermethylation RNA cap trimethylguanosine synthase activity https://github.com/geneontology/go-ontology/issues/25717 https://github.com/geneontology/go-ontology/issues/26934 https://github.com/geneontology/go-ontology/issues/28404 RHEA:78479 cap hypermethylase activity snRNA methyltransferase activity RHEA:78471 RHEA:78475 A 2,2,7-trimethylguanosine (TMG) cap is found on many RNA polymerase II transcribed small noncoding RNAs including small nuclear RNA (snRNA), small nucleolar RNA (snoRNA) and telomerase RNA. It is also found on nematode mRNAs that undergo trans-splicing of a 5'-capped leader sequence. RHEA:78507 mah 2009-11-19T03:23:20Z Catalysis of two successive methyl transfer reactions from AdoMet to the N-2 atom of guanosine, thereby converting 7-methylguanosine in an RNA cap to 2,2,7 trimethylguanosine. GO:0071164 RNA trimethylguanosine synthase activity molecular_function small nuclear RNA methyltransferase activity