Coactivator CBP in the regulation of conceptus IFNτ gene transcription

Studies of ovine interferon‐tau (oIFNτ) 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 oIFNτ gene were identified; however, a molecular mechanism by which these factors regulate oIFNτ 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 oIFNτ gene transcription in a transient transfection system using human choriocarcinoma JEG3 cells. The oIFNτ 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 oIFNτ‐reporter construct; however, this coactivator had no effect on the oIFNτ‐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 oIFNτ 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 (Δ2‐36), suppressed oIFNτ gene transcription. These observations suggest that c‐jun and Ets‐2 are the most probable binding partners for CBP in the potentiation of oIFNτ gene transcription. Mol. Reprod. Dev. 65: 23–29, 2003. © 2003 Wiley‐Liss, Inc.