The C/EBPα BRM2 mutation abrogates physical interaction with E2F. Whole-cell protein lysates from K562 lines stably transfected with C/EBPα proteins shown on the left side were incubated with normal rabbit serum (NRS) or antibodies to C/EBPα. Immunoprecipitated proteins from equal number of cells were separated on SDS-PAGE and analyzed by Western analysis using an E2F4 antibody and then the same blot stripped and reprobed with an antibody recognizing C/EBPα. The third lane in each panel represents one twentieth of the amount of lysate in the absence of immunoprecipitation as a control.