Induction of AP-2alpha expression by adenoviral infection involves inactivation of the AP-2rep transcriptional corepressor CtBP1.

AP-2 transcription factors execute important functions during embryonic development and malignant transformation. Recently, we have isolated a transcriptional repressor of AP-2alpha expression, the novel Krüppel-related zinc finger protein AP-2rep (Klf12). Here, we show that repression of AP-2alpha transcription by AP-2rep is dependent on an N-terminal PVDLS motif that interacts specifically with the corepressor CtBP1 both in vivo and in vitro. This interaction motif was previously identified in the C-terminal region of the adenoviral oncoprotein E1A. Infection of both HeLa and PA-1 cells with adenovirus type 5 strongly induced AP-2alpha mRNA. Consistently, E1A was necessary and sufficient to mediate up-regulation of AP-2alpha. Transiently transfected wild-type E1A protein activated an AP-2rep sensitive cis-regulatory element of the AP-2alpha promoter, but E1A protein harboring a mutation in the PVDLS motif failed to activate. In summary, we conclude that the adenoviral oncoprotein E1A activates transcription from the endogenous AP-2alpha gene, an effect that involves transcriptional derepression of the AP-2alpha promoter by interaction of E1A with the AP-2rep corepressor CtBP1.