1. ¹Hefei National Laboratory for Physical Sciences at Microscale and School of Life Sciences, University of Science and Technology of China, Hefei, Anhui, People's Republic of China
2. ²Division of Biology, California Institute of Technology, Pasadena, CA, USA

Correspondence: Dr M Wu, Hefei National Laboratory for Physical Sciences at Microscale and School of Life science, University of Science and Technology of China, N0. 96, Huangshan Road, Hefei, Anhui 230027, People's Republic of China. E-mail: wumian@ustc.edu.cn

³These authors contributed equally to this work.

Received 6 April 2009; Revised 24 August 2009; Accepted 30 August 2009; Published online 9 November 2009.

Abstract

Although Myc-interacting zinc-finger protein-1 (Miz-1) is known to be a poxvirus and zinc-finger (POZ) transcription factor required for Myc transcriptional repression, additional regulatory function of Miz-1 is less well understood. Using a yeast two-hybrid screen, we identified human alternate reading frame (ARF) protein as a novel interaction 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, thus to diminish the binding of p53 to its target promoter and inhibit p53-mediated gene transcription. Interestingly, the 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 both in vitro binding assay and competitive chromatin immunoprecipitation assay using a bona fide p53 endogenous Bax and Puma promoters. Thus, our study reveals that Miz-1 acts as a p53 suppressor by interfering with p53 DNA-binding ability, and ARF is 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.