Transcriptional regulation of the AP-2 alpha promoter by BTEB-1 and AP-2rep, a novel wt-1/egr-related zinc finger repressor

AP-2 transcription factors have been suggested to exert key regulatory func tions in vertebrate embryonic development, in tumorigenicity of various can cer cell types, and in controlling cell cycle and apoptotic effector genes. In this study, we investigated transcriptional regulation of the AP-2 alph a gene promoter mediated by an autoregulatory element (referred to as A32) with a core consensus AP-2 binding site at position -336 relative to the mR NA initiation site. AP-2 and multiple different nuclear proteins in HeLa an d Neuro2A cell extracts form specific bandshifts with the A32 element. By s creening a mouse brain cDNA expression library, we isolated two different c DNAs encoding the transcription factor BTEB-1 and a novel zinc finger prote in, AP-2rep. AP-2rep reveals a modular structure with homology to transcrip tion factors of the wt-1/egr-1-family. AP-2rep, BTEB-1, and AP-2 interact i n a mutually exclusive manner with overlapping binding sites in the A32 ele ment. Transfection studies revealed that BTEB-1 is a strong activator of AP -2 alpha promoter activity, whereas cotransfected AP-2 alpha resulted in mo derate autoactivation of promoter activity. In contrast, AP-2rep confers st rong transcriptional repression to the AP-2 alpha gene, and we observed an excellent correlation between induction of AP-2rep mRNA expression and down regulation of AP-2 alpha mRNA during development of the kidney. In summary, we have identified multiple transcription factors and cloned from an expre ssion library a novel zinc finger silencing factor, AP-2rep, mediating posi tive and negative regulation of AP-2 alpha expression through a set of over lapping cis-regulatory promoter elements.