 The promoter is bound by a repressor molecule called the cell-cycle-responsive element (CCRE).E2F binds to an E2F binding site on the CCRE, releasing the repressor from the promoter and allowing the transcription of cyclin A. Cyclin A/CDK2 will eventually phosphorylate E2F when cyclin A reaches a certain level, completing the negative feedback loop.Phosphorylation of E2F turns the transcription factor off, providing another level of controlling the transcription of cyclin A.