title: Epigenetic regulation of the X-chromosomal macrosatellite repeat encoding for the cancer/testis gene CT47.
abstract: Macrosatellite repeats (MSRs) present an extreme example of copy number variation, yet their epigenetic regulation in normal and malignant cells is largely understudied. The CT47 cancer/testis antigen located on human Xq24 is organized as an array of 4.8 kb large units. CT47 is expressed in the testis and in certain types of cancer, but not in non-malignant somatic tissue. We used CT47 as a model to study a possible correlation between copy number variation, epigenetic regulation and transcription originating from MSRs in normal and malignant cells. In lymphoblastoid cell lines and primary fibroblasts, CT47 expression was absent, consistent with the observed heterochromatic structure and DNA hypermethylation of the CT47 promoter. Heterochromatinization of CT47 occurs early during development as human embryonic stem cells show high levels of DNA methylation and repressive chromatin modifications in the absence of CT47 expression. In small-cell lung carcinoma cell lines with low levels of CT47 transcripts, we observed reduced levels of histone 3 lysine 9 trimethylation (H3K9me3) and trimethylated lysine 27 of histone H3 (H3K27me3) without concomitant increase in euchromatic histone modifications. DNA methylation levels in the promoter region of CT47 are also significantly reduced in these cells. This supports a model in which during oncogenic transformation, there is a relative loss of repressive chromatin markers resulting in leaky expression of CT47. We conclude that some MSRs, like CT47 and the autosomal MSRs TAF11-Like, PRR20, ZAV and D4Z4, the latter being involved in facioscapulohumeral muscular dystrophy, seem to be governed by common regulatory mechanisms with their abundant expression mostly being restricted to the germ line.
authors.affiliation: Department of Human Genetics, Leiden University Medical Center, Leiden, The Netherlands.
authors.forename: Judit
authors.initials: J
authors.lastname: Balog
authors.forename: Dan
authors.initials: D
authors.lastname: Miller
authors.forename: Elena
authors.initials: E
authors.lastname: Sanchez-Curtailles
authors.forename: Jose
authors.initials: J
authors.lastname: Carbo-Marques
authors.forename: Gregory
authors.initials: G
authors.lastname: Block
authors.forename: Marco
authors.initials: M
authors.lastname: Potman
authors.forename: Peter
authors.initials: P
authors.lastname: de Knijff
authors.forename: Richard J L F
authors.initials: RJ
authors.lastname: Lemmers
authors.forename: Stephen J
authors.initials: SJ
authors.lastname: Tapscott
authors.forename: Silvère M
authors.initials: SM
authors.lastname: van der Maarel
mesh_terms: D000951:Antigens, Neoplasm; D002460:Cell Line; D002843:Chromatin / Q000378:metabolism; D041321:Chromosomes, Human, X; D019175:DNA Methylation; D044127:Epigenesis, Genetic; D005260:Female; D023061:Gene Order; D006570:Heterochromatin / Q000235:genetics / Q000378:metabolism; D006657:Histones / Q000378:metabolism; D006801:Humans; D008297:Male; D011401:Promoter Regions, Genetic; D011506:Proteins / Q000235:genetics*; D012333:RNA, Messenger / Q000378:metabolism; D020080:Tandem Repeat Sequences
chemical_list: D000951:Antigens, Neoplasm; C510983:CT47A11 protein, human; D002843:Chromatin; D006570:Heterochromatin; D006657:Histones; D011506:Proteins; D012333:RNA, Messenger