Tumor Suppressor p16INK4A Regulates Polycomb-mediated DNA Hypermethylation in Human Mammary Epithelial Cells

• Published in: The Journal of biological chemistry Vol. 281; no. 34; pp. 24790 - 24802
• Main Authors: Reynolds, Paul A., Sigaroudinia, Mahvash, Zardo, Giuseppe, Wilson, Matthew B., Benton, Geoffrey M., Miller, Caroline J., Hong, Chibo, Fridlyand, Jane, Costello, Joseph F., Tlsty, Thea D.
• Format: Journal Article
• Language: English
• Published: United States Elsevier Inc 25.08.2006; American Society for Biochemistry and Molecular Biology
• Subjects: Carrier Proteins - genetics; Carrier Proteins - metabolism; Cell Line, Tumor; Cyclin-Dependent Kinase Inhibitor p16 - genetics; Cyclin-Dependent Kinase Inhibitor p16 - metabolism; DNA Methylation; DNA-Binding Proteins - genetics; DNA-Binding Proteins - metabolism; Enhancer of Zeste Homolog 2 Protein; Female; Gene Expression Regulation, Neoplastic; Gene Silencing; Homeodomain Proteins - genetics; Homeodomain Proteins - metabolism; Humans; Nuclear Proteins; Polycomb Repressive Complex 2; Polycomb-Group Proteins; Repressor Proteins - genetics; Repressor Proteins - metabolism; Transcription Factors - genetics; Transcription Factors - metabolism
• ISSN: 0021-9258; 1083-351X
• DOI: 10.1074/jbc.M604175200

Alterations in DNA methylation are important in cancer, but the acquisition of these alterations is poorly understood. Using an unbiased global screen for CpG island methylation events, we have identified a non-random pattern of DNA hypermethylation acquired in p16-repressed cells. Interestingly, this pattern included loci located upstream of a number of homeobox genes. Upon removal of p16INK4A activity in primary human mammary epithelial cells, polycomb repressors, EZH2 and SUZ12, are up-regulated and recruited to HOXA9, a locus expressed during normal breast development and epigenetically silenced in breast cancer. We demonstrate that at this targeted locus, the up-regulation of polycomb repressors is accompanied by the recruitment of DNA methyltransferases and the hypermethylation of DNA, an endpoint, which we show to be dependent on SUZ12 expression. These results demonstrate a causal role of p16INK4A disruption in modulating DNA hypermethylation, and identify a dynamic and active process whereby epigenetic modulation of gene expression is activated as an early event in breast tumor progression.