TGS1
Function
Catalyzes the 2 serial methylation steps for the conversion of the 7-monomethylguanosine (m(7)G) caps of snRNAs and snoRNAs to a 2,2,7-trimethylguanosine (m(2,2,7)G) cap structure. The enzyme is specific for guanine, and N7 methylation must precede N2 methylation. Hypermethylation of the m7G cap of U snRNAs leads to their concentration in nuclear foci, their colocalization with coilin and the formation of canonical Cajal bodies (CBs). Plays a role in transcriptional regulation.
Sequence Similarities
Belongs to the methyltransferase superfamily. Trimethylguanosine synthase family.
Tissue Specificity
Ubiquitously expressed. High expression in heart, skeletal muscle, kidney, liver and placenta.
Cellular localization
- Cytoplasm
- Nucleus
- Cajal body
- Nucleus
- Nucleolus
- A 90 kDa isoform is found in the nucleus while a 55 kDa isoform is found in the cytoplasm and colocalizes with the tubulin network.
Alternative names
HCA137, NCOA6IP, PIMT, TGS1, Trimethylguanosine synthase, CLL-associated antigen KW-2, Cap-specific guanine-N(2) methyltransferase, Hepatocellular carcinoma-associated antigen 137, Nuclear receptor coactivator 6-interacting protein, PRIP-interacting protein with methyltransferase motif, PIPMT