HLA-E is the only class I gene that escapes CpG methylation and is transcriptionally active in the trophoblast-derived human cell line JAR.
Polymorphic as well as HLA-F and -G genes are repressed in the human cell line JAR, derived from a tumor of trophoblast origin. By contrast, the HLA-E gene as well as the non-HLA novel coding-sequence, R1, located 5' to HLA-E, both remain transcriptionally active. We first demonstrated the role of DNA methylation in the repression of class I genes (except HLA-E) in JAR by the use of the 5-Azacytidine demethylating agent. Following treatment, JAR clones reexpressed polymorphic class I transcripts and cell surface alpha chains. Using methylation-sensitive rare cutter enzymes on JAR genomic DNA, followed by classical or pulse field gel electrophoresis and hybridization with HLA locus-specific probes, we found methylated CpG islands in the 5' region of all class I genes, except for HLA-E. These results, establishing an inverse relationship between states of methylation and transcriptional activity within the MHC class I chromosomal region in JAR, and the observations that the HLA-E and R1 genes were ubiquitously expressed, suggest that the HLA-E chromosomal domain might have functional importance including the presence of housekeeping genes.
Boucraut
J
J
Laboratoire d'Immunologie, Faculté de Médecine de la Timone, Marseille, France.
Guillaudeux
T
T
Alizadeh
M
M
Boretto
J
J
Chimini
G
G
Malecaze
F
F
Semana
G
G
Fauchet
R
R
Pontarotti
P
P
Le Bouteiller
P
P
D001374:Azacitidine / Q000494:pharmacology; D001483:Base Sequence; D002822:Choriocarcinoma / Q000235:genetics*; D016521:Electrophoresis, Gel, Pulsed-Field; D005786:Gene Expression Regulation; D005796:Genes; D005805:Genes, MHC Class I; D006680:HLA Antigens / Q000235:genetics*; D015395:Histocompatibility Antigens Class I / Q000235:genetics*; D066298:In Vitro Techniques; D008745:Methylation; D008969:Molecular Sequence Data; D009838:Oligodeoxyribonucleotides / Q000737:chemistry; D011110:Polymorphism, Genetic; D012150:Polymorphism, Restriction Fragment Length; D012333:RNA, Messenger / Q000235:genetics; D015183:Restriction Mapping; D014158:Transcription, Genetic; D014407:Tumor Cells, Cultured; D000097625:HLA-E Antigens
D001374:Azacitidine; D006680:HLA Antigens; D015395:Histocompatibility Antigens Class I; D009838:Oligodeoxyribonucleotides; D012333:RNA, Messenger; D000097625:HLA-E Antigens