Abstract
The female sex steroid hormone oestrogen stimulates both cell proliferation and cell differentiation in target tissues. These biological actions are mediated primarily through nuclear oestrogen receptors (ERs). The ligand-dependent transactivation of ERs requires several nuclear co-regulator complexes; however, the cell-cycle-dependent associations of these complexes are poorly understood. By using a synchronization system, we found that the transactivation function of ERalpha at G2/M was lowered. Biochemical approaches showed that ERalpha associated with two discrete classes of ATP-dependent chromatin-remodelling complex in a cell-cycle-dependent manner. The components of the NuRD-type complex were identified as G2/M-phase-specific ERalpha co-repressors. Thus, our results indicate that the transactivation function of ERalpha is cell-cycle dependent and is coupled with a cell-cycle-dependent association of chromatin-remodelling complexes.