Mitogenic stimulation of quiescent cells results in the expression of new gene products that play a role in monitoring the extracellular environment relative to the progression of cells through the cell cycle. We have cloned a mitogen-induced gene from T cells, GEM, that encodes a GTP-binding protein that is a novel member of the ras family. Ras proteins and their relatives function as regulatory binary switches in the cell, cycling between active and inactive states. GEM protein is transiently expressed in mid-G1 between 4 and 8 hours after activation. Several lines of evidence suggest that GEM may play a role in signal transduction during G1 progression. The biological role of GEM is being investigated by utilizing constitutively activated (low GTPase activity) or dominant negative forms of GEM.
