What's taking so long? S-phase entry from quiescence versus proliferation

Abstract

There is a short window in the mammalian cell cycle during which cells can respond to extracellular cues by withdrawing temporarily from the cell cycle. When these cells re-enter the cell cycle, they require several extra hours in the G1 phase before they replicate their DNA compared with their cycling counterparts. More than 20 years after this initial observation, we still do not understand what is taking so long.