Anti-2,2,7-trimethylguanosine (m3G/TMG) mAb

Small nuclear RNA (snRNA) is known to be involved in pre-mRNA splicing as an RNA component of snRNP. 2,2,7-trimethylated guanosine (m₃G/TMG) is a modified nucleoside at the 5’-cap site of U snRNAs except for U6 snRNA. Shortly after transcription, 7-methylguanosine (m⁷G), called cap structure, is added to 5’-end of newly synthesized U snRNA and m⁷G-capped U snRNA is exported to the cytoplasm. The m⁷G-cap is converted to m₃G-cap, which is a hypermethylated structure of 5’-end, by cytoplasmic catalytic protein TSG1 and the m₃G-capped U snRNA forms snRNP with Sm proteins in the cytoplasm, followed by entry into the nucleus. The m₃G-capped snRNP plays a role in regulation of pre-mRNA splicing as a part of spliceosome in nucleus. It is also reported that U3 and U8 snoRNA, localized to Cajal body during RNP biogenesis, possess m₃G-cap structure.