p53 negatively regulates cdc2 transcription via the CCAAT-binding NF-Y transcription factor

The p53 tumor suppressor protein regulates the transcription of regulatory genes involved in cell cycle arrest and apoptosis. We have reported previou sly that inducible expression of the p53 gene leads to the cell cycle arres t both at G(1) and G(2)/M in association with induction of p21 and reductio n of mitotic cyclins (cyclin A and B) and cdc2 mRNA. In this study, we inve stigated the mechanism by which p53 regulates transcription of the cdc2 gen e. Transient transfection analysis showed that wild type p53 represses wher eas various dominant negative mutants of p53 increase cdc2 transcription; T he cdc2 promoter activity is not repressed in cells transfected with a tran sactivation mutant, p53(22/23). An adenovirus oncoprotein, E1B-55K inhibits the p53-mediated repression of the cdc2 promoter, while E1B-19K does not. Since the cdc2 promoter does not contain a TATA sequence, we performed dele tion and point mutation analyses and identified the inverted CCAAT sequence located at -76 as a cis-acting element for the p53-mediated regulation. We found that a specific DNA-protein complex is formed at the CCAAT sequence and that this complex contains the NF-Y transcription factor. Consistently, a dominant negative mutant of the NF-YA subunit, NF-YAm29, decreases the c dc2 promoter, and p53 does not further decrease! the promoter activity in t he presence of NF-YAm29. These results suggest that p53 negatively regulate s cdc2 transcription and that the NF-Y transcription factor is required for the p53-mediated regulation.