Fig. 7. The mitotic-to-endocycle transition in Drosophila follicle cells is executed by Notch-dependent control of cell cycle regulators. (A) A proposed scheme showing that the Notch pathway induces a switch from the mitotic-to-endocycle by controlling the activity of key cell-cycle regulators; cyclin-dependent kinases that control M- and S-phase entry and the APC/ubiquitination complex that regulates degradation of cyclins. Notch activity controls these regulators by downregulating String and Dacapo, and activating Hec1/Cdh^Fzr. (B) The molecular model in which Notch activity executes the mitotic-to-endocycle switch by regulating all three major cell cycle transitions. Repression of String blocks M-phase, activation of Hec1/Cdh^Fzr allows G1 progression and repression of Dacapo assures entry into S-phase.