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First published online June 14, 2004
In this issue |
Usually, each step in the cell cycle depends on the completion of the previous stage. But some cells for example, cardiomyocytes, Drosophila egg follicle cells and many cancer cells can endocycle, where DNA synthesis continues without mitosis. On p. 3169, Shcherbata and colleagues investigate how Notch signalling controls the mitotic-to-endocytic transition in Drosophila follicle cells at mid-oogenesis. By identifying genes whose transcription is responsive to Notch at this transition, the researchers show that Notch activity: (1) blocks the mitotic (M) phase of the cycle by downregulating the G2/M regulator String; (2) allows G1 entry by activating Hec/CdhFrz, a regulator of the APC ubiquitination complex; and (3) ensures S-phase entry by repressing Dacapo, a cyclinE/CDK complex inhibitor. As the researchers discuss, a better understanding of how external signalling pathways control physiological cell-cycle transitions could identify how abnormal cell-cycle control occurs in cancer cells.
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