Epigenetic silencing of the immunoglobulin heavy-chain gene in classical Hodgkin lymphoma-derived cell lines contributes to the loss of immunoglobulin expression.
Immunoglobulin production is impaired in Hodgkin and Reed-Sternberg (HRS) cells of classical Hodgkin lymphoma (cHL) in spite of functional clonal rearrangements. The presence of "crippling" mutations in coding and regulatory regions, as well as down-regulation of B-cell-specific transcription factors, has been suggested as a potential reason for the lack of immunoglobulin (Ig) chain gene transcription. We have investigated the impact of epigenetic silencing in suppressing Ig heavy (H)-chain expression. Chromatin immunoprecipitation (ChIP) was used to analyze transcription factor binding to octamer motifs present in the IgH regulatory regions. Transcription factors were bound to these motifs in control cell lines, however, they were absent in the cHL-derived cell lines KMH2, L1236, and L428. Ectopic expression of octamer-binding transcription factor (Oct2) and/or B-cell Oct binding protein/Oct-binding factor (BOB.1/OBF.1) did not result in any measurable binding to these sites. Increased histone 3 Lysine 9 (H3-K9) methylation was observed in the promoter region of the IgH locus in L428 and L1236 cells. This is a typical feature of heterochromatic, transcriptionally silent regions. Treatment of cHL-derived cell lines with the DNA demethylating agent 5-aza-2'-deoxycytidine (5-aza-dC) partially reactivated IgH transcription and affected chromatin modifications. Our results suggest an important role of epigenetic silencing in the inhibition of IgH transcription in HRS cells.
Department of Physiological Chemistry, University of Ulm, D-89069, Ulm, Germany.
Alexey
A
Ushmorov
Olga
O
Ritz
Michael
M
Hummel
Frank
F
Leithäuser
Peter
P
Möller
Harald
H
Stein
Thomas
T
Wirth
D000964:Antimetabolites, Antineoplastic / Q000494:pharmacology; D001374:Azacitidine / Q000031:analogs & derivatives* / Q000494:pharmacology; D002051:Burkitt Lymphoma; D045744:Cell Line, Tumor; D019175:DNA Methylation; D000077209:Decitabine; D015536:Down-Regulation / Q000276:immunology; D044127:Epigenesis, Genetic / Q000276:immunology*; D015972:Gene Expression Regulation, Neoplastic / Q000276:immunology; D020868:Gene Silencing / Q000276:immunology*; D006689:Hodgkin Disease / Q000276:immunology* / Q000503:physiopathology*; D006801:Humans; D007143:Immunoglobulin Heavy Chains / Q000235:genetics*; D050813:Octamer Transcription Factor-2 / Q000378:metabolism; D011401:Promoter Regions, Genetic; D015534:Trans-Activators / Q000235:genetics / Q000378:metabolism; D014157:Transcription Factors / Q000378:metabolism; D014158:Transcription, Genetic / Q000187:drug effects / Q000276:immunology
D000964:Antimetabolites, Antineoplastic; D007143:Immunoglobulin Heavy Chains; D050813:Octamer Transcription Factor-2; C091546:POU2AF1 protein, human; D015534:Trans-Activators; D014157:Transcription Factors; D000077209:Decitabine; D001374:Azacitidine