An autonomous cell‐cycle oscillator involved in the coordination of G1 events

In early embryonic development, the cell cycle is paced by a biochemical oscillator involving cyclins and cyclin‐dependent kinases (cdks). Essentially the same machinery operates in all eukaryotic cells, although after the first few divisions various braking mechanisms (the so‐called checkpoints) become significant. Haase and Reed have recently shown that yeast cells have a second, independent oscillator which coordinates some of the events of the G1 phase of the cell cycle.(1) Although the biochemical nature of this oscillator is not known,it seems unlikely to be a redundant cyclin/cdk system. BioEssays 22:3–5, 2000. ©2000 John Wiley & Sons, Inc.