Topography of the predifferentiation GD growth arrest state relative to other growth arrest states in the G1 phase of the cell cycle.

The differentiation of 3T3 T proadipocytes is preceded by growth arrest at a state in the G1 phase of the cell cycle (GD) which is distinct from other G1 growth arrest states including those induced by serum deprivation (GS) or nutrient deprivation (GN) (Scott et al., 1982). We now report that the GD, GS, and GN arrest states are also distinct in their topography in G1. This conclusion was derived from kinetic studies which measured the time required for cells arrested at various G1 states to synthesize DNA and from studies on the ability of GD-, GS-, or GN-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 G1 phase of the cell cycle, the following arrest state topography exists: GD, GS, GN.