title: Damage-inducible intragenic demethylation of the human TP53 tumor suppressor gene is associated with transcription from an alternative intronic promoter.
abstract: Wild-type TP53 exons 5-8 contain CpG dinucleotides that are prone to methylation-dependent mutation during carcinogenesis, but the regulatory effects of methylation affecting these CpG sites are unclear. To clarify this, we first assessed site-specific TP53 CpG methylation in normal and transformed cells. Both DNA damage and cell ageing were associated with site-specific CpG demethylation in exon 5 accompanied by induction of a truncated TP53 isoform regulated by an adjacent intronic promoter (P2). We then synthesized novel synonymous TP53 alleles with divergent CpG content but stable encodement of the wild-type polypeptide. Expression of CpG-enriched TP53 constructs selectively reduced production of the full-length transcript (P1), consistent with a causal relationship between intragenic demethylation and transcription. 450K methylation comparison of normal (TP53-wildtype) and cancerous (TP53-mutant) human cells and tissues revealed focal cancer-associated declines in CpG methylation near the P1 transcription start site, accompanied by rises near the alternate exon 5 start site. These data confirm that site-specific changes of intragenic TP53 CpG methylation are extrinsically inducible, and suggest that human cancer progression is mediated in part by dysregulation of damage-inducible intragenic CpG demethylation that alters TP53 P1/P2 isoform expression. © 2015 The Authors. Molecular Carcinogenesis Published by Wiley Periodicals, Inc.
authors.affiliation: Laboratory of Genome Evolution, The Kinghorn Cancer Centre, Garvan Institute for Medical Research, Sydney, Australia.|UNSW Medicine, St. Vincent's Clinical School, Darlinghurst, Sydney, Australia.
authors.forename: James
authors.initials: J
authors.lastname: Blackburn
authors.affiliation: Laboratory of Cancer Biology, The Kinghorn Cancer Centre, Garvan Institute for Medical Research, Sydney, Australia.
authors.forename: Daniel L
authors.initials: DL
authors.lastname: Roden
authors.affiliation: Laboratory of Genome Evolution, The Kinghorn Cancer Centre, Garvan Institute for Medical Research, Sydney, Australia.|UNSW Medicine, St. Vincent's Clinical School, Darlinghurst, Sydney, Australia.
authors.forename: Robert
authors.initials: R
authors.lastname: Ng
authors.affiliation: Laboratory of Cancer Bioinformatics, The Kinghorn Cancer Centre, Garvan Institute for Medical Research, Sydney, Australia.
authors.forename: Jianmin
authors.initials: J
authors.lastname: Wu
authors.affiliation: Laboratory of Developmental and Stem Cell Biology, Victor Chang Cardiac Research Institute, Sydney, Australia.
authors.forename: Alexis
authors.initials: A
authors.lastname: Bosman
authors.affiliation: Laboratory of Genome Evolution, The Kinghorn Cancer Centre, Garvan Institute for Medical Research, Sydney, Australia.|UNSW Medicine, St. Vincent's Clinical School, Darlinghurst, Sydney, Australia.|Clinical Informatics & Research Centre, Department of Oncology, St. Vincent's Hospital, Sydney, Australia.
authors.forename: Richard J
authors.initials: RJ
authors.lastname: Epstein
mesh_terms: D000818:Animals; D001483:Base Sequence; D018938:Caco-2 Cells; D002460:Cell Line; D045744:Cell Line, Tumor; D018899:CpG Islands; D004249:DNA Damage; D019175:DNA Methylation; D005091:Exons; D015972:Gene Expression Regulation, Neoplastic; D016158:Genes, p53; D006801:Humans; D007438:Introns; D051379:Mice; D009369:Neoplasms / Q000235:genetics*; D011401:Promoter Regions, Genetic; D015533:Transcriptional Activation; D016159:Tumor Suppressor Protein p53 / Q000235:genetics*
chemical_list: D016159:Tumor Suppressor Protein p53
keywords: DNA methylation; TP53; cancer; epigenetics; transcriptional regulation; tumor suppressor gene