ARF Antagonizes The Ability Of Miz-1 To Inhibit P53-mediated Transactivation

Although Miz-1 is known to be a POZ-zinc finger transcription factor required for Myc transcriptional repression, additional regulatory role of Miz-1 has remained less understood. Here we report that by yeast two-hybrid screen, p14ARF was found to be a novel interacting partner of Miz-1. The zinc finger domain of Miz-1 is involved in its binding to ARF. In addition, we found that Miz-1 was able to interact with p53 through its DNA binding domain (DBD), thus to diminish the binding of p53 to its target promoter and inhibit p53-mediated gene transcription. This Miz-1-regulated p53 transcriptional suppression does not require the presence of ARF or Mdm2. Importantly, ARF and p53 were found to competitively bind to Miz-1 in regulating p53-mediated transcription, and this conclusion was verified by competitive ChIP assay using a bona fide p53 endogenous Bax promoter. Thus our study reveals that Miz-1 is a p53 suppressor by interfering with p53 DNA-binding ability, and ARF was able to counteract the suppression of Miz-1 on p53 by direct binding to Miz-1, suggesting that Miz-1 is a novel mediator in the ARF-p53 pathway.