Figure 5.

Model for diminished replicative lifespan of mother cells that have reentered the cell cycle after stationary phase. In control (nonstarved) cells, replicative aging of mother cells (solid time line) is caused by the sum of two processes, the accumulation of ERCs and the parallel accumulation of something else, termed X. These signals are summed and at some threshold elicit the aging phenotypes of sterility, nucleolar fragmentation, and growth arrest. Stationary-phase cells (starved) accumulate X while in stationary phase (dotted time line), so that their aging is advanced when they commence replicative growth (solid time line).