Zac1 functional interactions mediate AP-1 transcriptional activity

► Zac1 enhanced PMA-induced AP-1 activity in HeLa and HeLa/p53 shRNA cells. ► Zac1 physically and functionally interacted with AP-1 (c-Jun, c-Fos, or both) proteins. ► Zac1 functioned as a selective coactivator for AP-1-dependent transcription. ► Zac1 interplayed with PMA on the sub-G1 phase via the phosphorylation of H2A.X.