Endogenous E2F-1 promotes timely G(0) exit of resting mouse embryo fibroblasts

Much evidence strongly suggests a positive role for one or more E2F species in the control of exit from G(0)/G(1). Results described here provide direct evidence that endogenous E2F-1, as predicted, contributes to progression from G(0) to S. By contrast, cycling cells lacking an intact E2F-1 gene demonstrated normal cell cycle distribution. Therefore, E2F-1 exerts a unique function leading to timely G(0) exit of resting cultured primary cells, while at the same time being unnecessary for normal G(1) to S phase progression of cycling cells.