title: Gene silencing of MIR22 in acute lymphoblastic leukaemia involves histone modifications independent of promoter DNA methylation.
abstract: Aberrant epigenetic regulation has recently been implicated in the downregulation of tumour suppressor microRNAs (miRNAs). Histone modification and DNA methylation can have different roles in gene silencing in cancer. To investigate whether histone modifications would contribute to the dysregulation of miRNAs in acute lymphoblastic leukaemia (ALL), the effect of a histone deacetylase inhibitor, trichostatin A (TSA), on miRNA expression profile was analysed by microarray assay in a precursor B-cell ALL cell line NALM-6. A total of 10 miRNAs were downregulated and 31 were upregulated significantly following TSA treatment. Among TSA-upregulated miRNAs, MIR22 is an extronic miRNA and resides in the second exon of the non-coding transcript MGC14376. Upregulation of MIR22 transcription was found in both NALM-6 cells and primary human ALL malignant cells treated with TSA. Whereas a CpG island was identified within the promoter element of MIR22, no promoter DNA methylation was detected in these cells. In contrast, accumulation of the repressive histone marker H3K27 trimethylation (H3K27triM) was identified around the transcriptional start point of the gene, which was reduced by TSA treatment. Thus, accumulation of H3K27triM independent of promoter DNA methylation may be a novel epigenetic mechanism for MIR22 silencing in ALL.
authors.affiliation: Institute of Hematology, Union Hospital, Wuhan, China.
authors.forename: Xiaoqing
authors.initials: X
authors.lastname: Li
authors.forename: Jun
authors.initials: J
authors.lastname: Liu
authors.forename: Rui
authors.initials: R
authors.lastname: Zhou
authors.forename: Shi
authors.initials: S
authors.lastname: Huang
authors.forename: Shiang
authors.initials: S
authors.lastname: Huang
authors.forename: Xian-Ming
authors.initials: XM
authors.lastname: Chen
mesh_terms: D001374:Azacitidine / Q000031:analogs & derivatives / Q000494:pharmacology; D018899:CpG Islands / Q000235:genetics; D019175:DNA Methylation / Q000235:genetics*; D004273:DNA, Neoplasm / Q000235:genetics; D000077209:Decitabine; D044127:Epigenesis, Genetic; D020869:Gene Expression Profiling / Q000379:methods; D015972:Gene Expression Regulation, Neoplastic / Q000187:drug effects; D020868:Gene Silencing; D052138:Genes, Neoplasm / Q000235:genetics; D056572:Histone Deacetylase Inhibitors / Q000494:pharmacology; D006657:Histones / Q000235:genetics*; D006801:Humans; D006877:Hydroxamic Acids / Q000494:pharmacology; D035683:MicroRNAs / Q000235:genetics*; D016133:Polymerase Chain Reaction / Q000379:methods; D054198:Precursor Cell Lymphoblastic Leukemia-Lymphoma / Q000235:genetics* / Q000378:metabolism; D011401:Promoter Regions, Genetic / Q000235:genetics*; D014407:Tumor Cells, Cultured
chemical_list: D004273:DNA, Neoplasm; D056572:Histone Deacetylase Inhibitors; D006657:Histones; D006877:Hydroxamic Acids; C548375:MIRN22 microRNA, human; D035683:MicroRNAs; C012589:trichostatin A; D000077209:Decitabine; D001374:Azacitidine