title: Mel-18, a polycomb group protein, regulates cell proliferation and senescence via transcriptional repression of Bmi-1 and c-Myc oncoproteins.
abstract: Polycomb group (PcG) protein Bmi-1 is an important regulator of cell proliferation. It regulates cellular senescence and proliferation of cells via the transcriptional repression of INK4a/ARF locus and other target genes. Here, we report that Mel-18, a PcG ring finger protein (PCGF) transcriptionally down-regulates Bmi-1. Furthermore, the expression of Bmi-1 and Mel-18 inversely correlates in proliferating and senescent human fibroblasts. Bmi-1 down-regulation by Mel-18 results in accelerated senescence and shortening of the replicative life span in normal human cells. Importantly, using promoter-reporter, chromatin immunoprecipitation, and quantitative real-time primary transcript RT-PCR assays, and an RNA interference approach, we demonstrate that Bmi-1 is a bona fide target of c-Myc oncoprotein. Finally, our data suggest that Mel-18 regulates Bmi-1 expression during senescence via down-regulation of c-Myc. These studies link c-Myc and polycomb function in cell proliferation and senescence.
authors.affiliation: Division of Cancer Biology and Department of Medicine, Evanston Northwestern Healthcare Research Institute, Evanston, IL 60201, USA.
authors.forename: Wei-Jian
authors.initials: WJ
authors.lastname: Guo
authors.forename: Sonal
authors.initials: S
authors.lastname: Datta
authors.forename: Vimla
authors.initials: V
authors.lastname: Band
authors.forename: Goberdhan P
authors.initials: GP
authors.lastname: Dimri
mesh_terms: D001665:Binding Sites; D049109:Cell Proliferation; D002478:Cells, Cultured; D016922:Cellular Senescence / Q000235:genetics*; D047369:Chromatin Immunoprecipitation; D015536:Down-Regulation; D005786:Gene Expression Regulation; D017930:Genes, Reporter; D006801:Humans; D009687:Nuclear Proteins / Q000037:antagonists & inhibitors / Q000235:genetics* / Q000378:metabolism; D063150:Polycomb Repressive Complex 1; D011401:Promoter Regions, Genetic; D011518:Proto-Oncogene Proteins / Q000037:antagonists & inhibitors / Q000235:genetics* / Q000378:metabolism; D016271:Proto-Oncogene Proteins c-myc / Q000235:genetics* / Q000378:metabolism; D034622:RNA Interference; D012097:Repressor Proteins / Q000037:antagonists & inhibitors / Q000235:genetics* / Q000378:metabolism*
chemical_list: C069077:BMI1 protein, human; C489427:MYC protein, human; D009687:Nuclear Proteins; C472312:PCGF6 protein, human; D011518:Proto-Oncogene Proteins; D016271:Proto-Oncogene Proteins c-myc; D012097:Repressor Proteins; D063150:Polycomb Repressive Complex 1