THE PUTATIVE TUMOR-SUPPRESSOR BIN1 IS A SHORT-LIVED NUCLEAR PHOSPHOPROTEIN, THE LOCALIZATION OF WHICH IS ALTERED IN MALIGNANT-CELLS

BIN1 is a putative tumor suppressor that was identified in a genetic s creen for polypeptides that interact with the MYC oncoprotein. Using a set of six monoclonal antibodies, we identified and examined biochemi cal features and localization of cellular BIN1, Epitope mapping indica ted that a putative nuclear localization motif and the MYC-binding dom ain were among the regions recognized by five antibodies, In immunopre cipitation and Western analyses, cellular BIN1 was identified in human and rodent cells as a monomeric phosphoprotein of M-r similar to 70,0 00, Pulse-chase experiments showed that BIN1 was short-lived, with a h alf-life of similar to 2 h, Cell immunofluorescence experiments reveal ed overlapping but unique nuclear localization patterns distinguished by two different antibodies, In normal cells, BIN1 was predominantly n ucleoplasmic but was also present in a subnuclear compartment, Convers ely, in a panel of tumor cells that expressed BIN1, the predominant lo calization was the subnuclear compartment. Taken together, the results suggested that the antibodies recognized different isoforms or confor mations of BIN1, the localization of which varied between normal and t umor cells, This study will facilitate further analysis of the structu re and regulation of BIN1 in normal and malignant cells.