RAC1 IS REQUIRED FOR CELL-PROLIFERATION AND G2 M PROGRESSION/

We have transiently expressed a dominant negative form of rad (N17rac1 ) using adenoviral-mediated gene transfer. The level of N17rac1 expres sion is demonstrated to be proportional to the multiplicity of infecti on. Expression of N17rac1 in Rat 2 fibroblasts results in cytostatic g rowth arrest. Cell-cycle analysis demonstrates that cells expressing N 17rac1 accumulate in G2/M. These results suggest that rad is required for cell proliferation and provide the first demonstration in mammalia n cells of a role for small GTP-binding proteins in the G2/M transitio n.