A serum-induced 29 Kd protein of mouse embryo fibroblasts is tightly bound to the chromatin

Abstract

Treatment of quiescent cultures of mouse embryo fibroblasts with 20% fetal calf serum (FCS) or cycloheximide (CH) resulted in the induction of a nuclear protein of molecular weight 29 000 daltons. The 29 Kd protein induced by these two agents was found to be tightly bound to the chromatin since it was not released from the chromatin by a combination of 2.5 M NaCl and 3.2 M urea. The chromatin associated CH-induced 29 Kd protein and the 29 Kd protein obtained from serum-induced cells displayed similar N-chlorosuccinimide cleavage patterns. Pulse-chase experiments indicate a half-life of an hour for the 29 Kd protein. The kinetics of induction of the 29 Kd protein in the early hours of mitogen addition, short half-life, nuclear localisation and strong association with chromatin suggest that this protein may have important roles in cell proliferation, possibly as a mediator of mitogen action.