Identification and characterization of Bmi-1-responding element within the human p16 promoter

J Biol Chem. 2010 Oct 22;285(43):33219-33229. doi: 10.1074/jbc.M110.133686. Epub 2010 Jun 15.

Abstract

Bmi-1, the first functionally identified polycomb gene family member, plays critical roles in cell cycle regulation, cell immortalization, and cell senescence. Bmi-1 is involved in the development and progression of carcinomas and is a potent target for cancer therapy. One important pathway regulated by Bmi-1 is that involving two cyclin-dependent kinase inhibitors, p16(Ink4a) and p19(Arf), as Bmi-1 represses the INK4a locus on which they are encoded. A close correlation between the up-regulation of Bmi-1 and down-regulation of p16 has been demonstrated in various tumors; however, how Bmi-1 regulates p16 expression is not clear. In this study, we revealed that Bmi-1 regulates the expression of p16 by binding directly to the Bmi-1-responding element (BRE) within the p16 promoter. The BRE resided at bp -821 to -732 upstream of the p16 ATG codon. BRE alone was sufficient to allow Bmi-1-mediated regulation of the CMV promoter. Bmi-1 typically functions by forming a complex with Ring2; however, regulation of p16 was independent of Ring2. Chromatin immunoprecipitation sequencing of Bmi-1-precipitated chromatin DNA revealed that 1536 genes were targeted by Bmi-1, including genes involved in tissue-specific differentiation, cell cycle, and apoptosis. By analyzing the binding sequences of these genes, we found two highly conserved Bmi-1-binding motifs, which were required for Bmi-1-mediated p16 promoter regulation. Taken together, our results revealed the molecular mechanism of Bmi-1-mediated regulation of the p16 gene, thus providing further insights into the functions of Bmi-1 as well as a sensitive high-throughput platform with which to screen Bmi-1-targeted small molecules for cancer therapy.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Cyclin-Dependent Kinase Inhibitor p16 / biosynthesis*
  • Cyclin-Dependent Kinase Inhibitor p16 / genetics
  • Gene Expression Regulation / physiology*
  • Genetic Loci / physiology*
  • HeLa Cells
  • Humans
  • Multiprotein Complexes / genetics
  • Multiprotein Complexes / metabolism
  • Neoplasms / drug therapy
  • Neoplasms / genetics
  • Neoplasms / metabolism
  • Nuclear Proteins / genetics
  • Nuclear Proteins / metabolism*
  • Polycomb Repressive Complex 1
  • Proto-Oncogene Proteins / genetics
  • Proto-Oncogene Proteins / metabolism*
  • Repressor Proteins / genetics
  • Repressor Proteins / metabolism*
  • Response Elements / physiology*
  • Tumor Suppressor Proteins / genetics
  • Tumor Suppressor Proteins / metabolism
  • Ubiquitin Thiolesterase / genetics
  • Ubiquitin Thiolesterase / metabolism

Substances

  • BAP1 protein, human
  • BMI1 protein, human
  • Cyclin-Dependent Kinase Inhibitor p16
  • Multiprotein Complexes
  • Nuclear Proteins
  • Proto-Oncogene Proteins
  • Repressor Proteins
  • Tumor Suppressor Proteins
  • Polycomb Repressive Complex 1
  • Ubiquitin Thiolesterase