Physical characteristics of a factor related to the c-myc/insulin promoter binding protein ZF87/Pur-1

The ZF87/Pur-1 factor is a zinc finger containing protein that binds to sites within the c-myc and insulin promoters. The open reading frame of the mRNA predicts a 49 kd protein which migrates as a 58 kd protein by SDS-PAGE. Antiserum to ZF87/Pur-1 recognizes the 58 kd protein in western blots of Hela cell nuclear extracts. The antiserum also specifically recognizes an 87 kd protein (p87) that is distributed between cytosolic and nuclear extracts. p87 found in cytosolic extracts sediments faster in a glycerol gradient than that found in nuclear extracts. These data indicate that p87 may associate with specific factors or undergo a post-translational modification that changes its conformation.