CELL-CYCLE-REGULATED EXPRESSION OF RAP1 IN REGENERATING LIVER

Rap1 proteins are capable of competing with Ras p21 for binding to eff ecters, and of antagonizing some Ras-induced effects, but their partic ipation in normal growth regulation has not been established The level of Rap1 protein and the expression of the rap1A gene were examined by immunoblotting and Northern analysis during the regenerative growth r esponse in rat Liver following partial hepatectomy. Protein and mRNA w ere significantly down-regulated prior to and during the onset of DNA synthesis. The timing of this effect is consistent with a model in whi ch expression of Rap1 is turned off or down to allow the initiation of proliferation. (C) 1997 Academic Press