MLL processing occurs within a few hours of its translation.
BOSC23 cells were transfected with empty vector (vector) or a construct encoding full-length MLL tagged with HA at its C-terminus [MLL(H)]. The cells were metabolically labeled with [35S]-methionine for 3 hours. After labeling, the cells were cultured in nonradioactive medium for the indicated time periods and then lysed in lysis buffer. MLL proteins were immunoprecipitated with anti-MLL antibody, separated in denaturing gels, and visualized by autoradiography (A and B) or immunoblotted with anti-HA (C and D) or anti-MLL N-terminal (E and F) antibodies. In the left panels (A, C, and E), the cells were harvested at 0, 3, and 9 hours after labeling. In the right panels (B, D, and F), the cells were harvested at 0, 1, and 2 days after labeling. Unprocessed MLL, the N-terminal fragment, and the C-terminal fragment are indicated by arrows.
