Transcription factor C/EBPβ and 17β-estradiol promote transcription of the porcine p53 gene.

The tumor protein 53 (p53) gene played a crucial role in maternal reproduction except its classic roles in maintaining genomic stability and preventing tumorigenesis. However, little is known concerning the regulatory elements which control the expression of p53 gene. In this study, we predicted two binding sites (-490/-477 and -405/-392) of transcription factor CCAAT/enhancer binding protein beta (C/EBPβ) within the core promoter (-985/-273) determined by promoter deletion analysis, and discovered that the second site (-405/-392) was important for p53 promoter activity by site-directed mutagenesis. Then the binding of C/EBPβ to the p53 promoter was identified by electrophoretic mobility shift assays (EMSA) and chromatin immunoprecipitation (ChIP). Moreover, evidence from C/EBPβ overexpression and RNAi studies showed C/EBPβ regulated p53 promoter activity and endogenous p53 expression. Meanwhile, we observed p53 mRNA at the peak in 10(-6)mol/L 17β-estradiol treated cells for 24h via enhancing its core promoter activity. Taken together, our study indicates that C/EBPβ and 17β-estradiol are the essential regulatory factors for p53 transcription.