Topography of the predifferentiation G D growth arrest state relative to other growth arrest states in the G 1 phase of the cell cycle

The differentiation of 3T3 T proadipocytes is preceded by growth arrest at a state in the G 1 phase of the cell cycle (G D ) which is distinct from other G 1 growth arrest states including those induced by serum deprivation (G S ) or nutrient deprivation (G N ) (Scott et al., 1982). We now report that the G D , G S , and G N arrest states are also distinct in their topography in G 1 . This conclusion was derived from kinetic studies which measured the time required for cells arrested at various G 1 states to synthesize DNA and from studies on the ability of G D ‐, G S ‐, or G N ‐arrested cells to be converted from one arrest state to another in the absence of DNA synthesis. The results suggest that relative to the start of the G 1 phase of the cell cycle, the following arrest state topography exists: G D , G S , G N .