STIMULATION OF CELL-PROLIFERATION BY CHROMOSOMAL NONHISTONE PROTEINS PP23

Chromatographically individual fractions (pp23) of chromosonal nonhist one proteins (NHP) of the rat and bovine kidney as well as of rat hepa tocellular tumors have been shown to be capable of inducing DNA synthe sis in the resting culture of the murine fibroblast line Swiss 3T3, i. e. these NHP fractions are able to take cells from G(0) to S phase and stimulate proliferation. at the same time, between the rat and bovine pp25 preparations there was a substantial difference in immunological properties and capability of initiating expression of a membrane anti gen of the kidney origin in the surviving rat hepatocyte culture. Thus , whereas all pp23 preparations have a common ability to stimulate cel l proliferation in culture, these preparations, at the same time, pres erve their functional species individuality.