This family includes TAR RNA-binding protein 1 (TARBP1), which is a probable S-adenosyl-L-methionine-dependent methyltransferase that methylates RNA molecules such as tRNAs. During infection by HIV-1, it binds to the loop region of TAR RNA, a region also bound by RNA polymerase II [, , ].
This entry represents the C-terminal methyltransferase domain of TARBP1 and Trm3 [].Yeast tRNA (guanosine(18)-2'-O)-methyltransferase Trm3 catalyses the formation of 2'-O-methylguanosine at position 18 (Gm18) in various tRNAs []. Trm3 is similar to C-terminal domain of TAR (HIV-1) RNA binding protein 1 (TARBP1), a protein binding to TAR, which functions as a RNA regulatory signal by forming a stable stem-loop structure to which transactivator protein Tat binds. The role of TARBP1 is believed to be to disengage RNA polymerase II from TAR during transcriptional elongation [, ].
This entry includes a group of putative methyltransferases, including TARBP1 from humans and Trm3 from Saccharomyces cerevisiae. TARBP1 (TAR RNA-binding protein 1) plays a role in HIV-1 infection by binding to the loop region of TAR RNA, a region also bound by RNA polymerase II [, , ]. Its dimerization may have a critical role in its activity []. Trm3 catalyses a specific methylation of the guanosine nucleotide at position 18 of the tRNAs. It is involved in the cellular response to oxidative stress, and its activity may play a role on innate response [, ].