Coactivator CBP in the regulation of conceptus IFNtau gene transcription

Studies of ovine interferon-tau (oIFNtau) gene regulation, an anti-luteolytic factor produced by conceptuses of the ruminant ungulates, have been carried out, but a definitive mechanism for its spatial-temporal transcription has not been elucidated. Recently, specific binding regions for transcription factors AP-1 and Ets-2 on the oIFNtau gene were identified; however, a molecular mechanism by which these factors regulate oIFNtau gene transcription has not been characterized. In the present study, we investigated the potential relationship between AP-1 and Ets-2, and their association with a coactivator, cAMP-response element binding protein-binding protein (CBP), on oIFNtau gene transcription in a transient transfection system using human choriocarcinoma JEG3 cells. The oIFNtau gene promoter/enhancer (-654 to + 1 bases, wild type)-luciferase reporter construct (pGL3-654) or its mutant at the AP-1 or Ets-2 site was cotransfected with CBP (pRc/RSV-CBP) construct along with c-jun, c-fos, and/or Ets-2 expression plasmid. CBP enhanced transcription of the wild type oIFNtau-reporter construct; however, this coactivator had no effect on the oIFNtau-reporter construct with mutated AP-1 or Ets-2 site. Cotransfection of CBP with c-jun and/or Ets-2, but not with c-fos, further increased oIFNtau gene transactivation although amounts of c-jun and c-fos expression, resulting from expression vectors, were similar. In addition, CBP inhibitor adenovirus 12S E1A (E1A), but not the mutant of E1A without CBP binding domain (Delta2-36), suppressed oIFNtau gene transcription. These observations suggest that c-jun and Ets-2 are the most probable binding partners for CBP in the potentiation of oIFNtau gene transcription. Mol. Reprod. Dev. 65: 23-29, 2003.