Cyclin A repression in quiescent cells is associated with chromatin remodeling of its promoter and requires Brahma/SN172α

Cell cycle-dependent expression of cyclin A is controlled by transcriptional repression in early phase of the cell cycle. In this study, we directly examine the chromatin structure of the mouse cyclin A promoter through in vivo micrococcal nuclease footprinting. We describe here that cyclin A repression is associated with two positioned nucleosomes and that histones progressively lose DNA contact synchronously with gene activation. This particular nucleosomal organization is disrupted bit mutations of the cyclin A bipartite repressor sequence. Moreover, the same sequence recruits the chromatin remodeling factor Brahma/SNF2alpha (Brm) onto the cyclin A promoter. Accordingly, cyclin A proximal promoter is not wrapped around nucleosomes and not repressed in quiescent cells lacking Brim. These results provide molecular explanations for the transcriptional repression state of cyclin A, as well as insights into the action of Brm chromatin remodeling factor as cell cycle regulator.