Upregulation of ATBF1 by progesterone-PR signaling and its functional implication in mammary epithelial cells

► Progesterone increases ATBF1 expression in vitro and in vivo. ► The induction of ATBF1 by progesterone is PR-dependent. ► Pg-activated PR directly binds to the ATBF1 promoter to induce its transcription. ► ATBF1 is necessary for Pg to induce the expansion of progenitor cells.