TARBP1 Background Information Probable methyltransferase TARBP1 (TAR (HIV-1) RNA binding protein 1), also known as TAR RNA-binding protein 1, TAR RNA-binding protein of 185 kDa (TRP-185) or TRM3, belongs to the RNA methyltransferase trmH family. TARBP1 binds to the loop region of TAR RNA in the event of HIV-1 infection, a region which is also bound by RNA polymerase II (Pol II). Research suggests that TARBP1 plays a role in disengaging Pol II from HIV-1 TAR RNA and may work in conjunction with HIV-1 Tat.TRBP2, also known as TARBP2 (Trans-activation-responsive (HIV-1) RNA binding protein 2), TRBP1 or TRBP, is a nuclear protein that contains three DRBM (double-stranded RNA-binding) domains. TRBP binds between the bulge and the loop of the HIV-1 TAR RNA regulatory element and activates HIV-1 gene expression in synergy with the viral Tat protein. The third DRBM motif in the C-terminus of human TRBP2 can interact with and inhibit PKR activity, thereby increasing HIV-1 long terminal repeat (LTR) expression. In addition, TRBP2 functions as a component of a Dicer-containing complex and associates with the catalytic subunit of the RNA-induced silencing complex (RISC), namely eIF2C2. TRBP2 is essential for Dicer stability and the proper assembly of RISC. This suggests that TRBP2, in association with Dicer, plays an important role in the processing of miRNAs (microRNAs).
