title: Evidence for alteration of EZH2, BMI1, and KDM6A and epigenetic reprogramming in human papillomavirus type 16 E6/E7-expressing keratinocytes.
abstract: A number of epigenetic alterations occur in both the virus and host cellular genomes during human papillomavirus (HPV)-associated carcinogenesis, and investigations of such alterations, including changes in chromatin proteins and histone modifications, have the potential to lead to therapeutic epigenetic reversion. We report here that transformed HPV16 E6/E7-expressing primary human foreskin keratinocytes (HFKs) (E6/E7 cells) demonstrate increased expression of the PRC2 methyltransferase EZH2 at both the mRNA and protein levels but do not exhibit the expected increase in trimethylated H3K27 (H3K27me3) compared to normal keratinocytes. In contrast, these cells show a reduction in global H3K27me3 levels in vitro, as well as upregulation of the KDM6A demethylase. We further show for the first time that transformation with the HPV16 E6 and E7 oncogenes also results in an increase in phosphorylated EZH2 serine 21 (P-EZH2-Ser21), mediated by active Akt, and in a downregulation of the PRC1 protein BMI1 in these cells. High-grade squamous cervical intraepithelial lesions also showed a loss of H3K27me3 in the presence of increased expression of EZH2. Correlating with the loss of H3K27me3, E6/E7 cells exhibited derepression of specific EZH2-, KMD6A-, and BMI1-targeted HOX genes. These results suggest that the observed reduction in H3K27me3 may be due to a combination of reduced activities/levels of specific polycomb proteins and increases in demethylases. The dysregulation of multiple chromatin proteins resulting in the loss of global H3K27me3 and the transcriptional reprogramming in HPV16 E6/E7-infected cells could provide an epigenetic signature associated with risk and/or progression of HPV16-associated cancers, as well as the potential for epigenetic reversion in the future.
authors.affiliation: Centre for Cancer Research and Cell Biology, School of Medicine, Dentistry and Biomedical Sciences, Queen's University Belfast, 97 Lisburn Road, Belfast BT9 7BL, United Kingdom.
authors.forename: Paula L
authors.initials: PL
authors.lastname: Hyland
authors.forename: Simon S
authors.initials: SS
authors.lastname: McDade
authors.forename: Rachel
authors.initials: R
authors.lastname: McCloskey
authors.forename: Glenda J
authors.initials: GJ
authors.lastname: Dickson
authors.forename: Ken
authors.initials: K
authors.lastname: Arthur
authors.forename: Dennis J
authors.initials: DJ
authors.lastname: McCance
authors.forename: Daksha
authors.initials: D
authors.lastname: Patel
mesh_terms: D002478:Cells, Cultured; D004268:DNA-Binding Proteins / Q000378:metabolism*; D000071221:Enhancer of Zeste Homolog 2 Protein; D044127:Epigenesis, Genetic; D020869:Gene Expression Profiling; D056466:Histone Demethylases / Q000378:metabolism*; D054884:Host-Pathogen Interactions; D052162:Human papillomavirus 16 / Q000472:pathogenicity*; D006801:Humans; D015603:Keratinocytes / Q000821:virology; D009687:Nuclear Proteins / Q000378:metabolism*; D009856:Oncogene Proteins, Viral / Q000378:metabolism*; D050725:Papillomavirus E7 Proteins / Q000378:metabolism*; D063150:Polycomb Repressive Complex 1; D063151:Polycomb Repressive Complex 2; D011518:Proto-Oncogene Proteins / Q000378:metabolism*; D012097:Repressor Proteins / Q000378:metabolism*; D014157:Transcription Factors / Q000378:metabolism*
chemical_list: C069077:BMI1 protein, human; D004268:DNA-Binding Proteins; C068651:E6 protein, Human papillomavirus type 16; D009687:Nuclear Proteins; D009856:Oncogene Proteins, Viral; D050725:Papillomavirus E7 Proteins; D011518:Proto-Oncogene Proteins; D012097:Repressor Proteins; D014157:Transcription Factors; C059731:oncogene protein E7, Human papillomavirus type 16; D056466:Histone Demethylases; C523998:KDM6A protein, human; C498409:EZH2 protein, human; D000071221:Enhancer of Zeste Homolog 2 Protein; D063151:Polycomb Repressive Complex 2; D063150:Polycomb Repressive Complex 1