WD Repeat Containing Domain Protein 77 (WDR77)

WDR77 is a component of the 20S PRMT5-containing methyltransferase complex, which modifies specific arginines to dimethylarginines in several spliceosomal Sm proteins . This modification targets Sm proteins to the survival of motor neurons (SMN) complex for assembly into small nuclear ribonucleoprotein core particles .

The deduced 342-amino acid protein has 6 WD repeats and has a calculated molecular mass of 36.7 kD. MEP50 had an apparent molecular mass of 50 kD.Protein pull-down assays revealed that MEP50 specifically interacted with SmB (SNRPB) and SmD2 (SNRPD2) and more weakly with SmD3 (SNRPD3) and SmE (SNRPE). Antibodies directed against MEP50 significantly reduced the arginine methyltransferase activity of the immunopurified complex toward Sm substrates.