Volume 148, Issue 1 pp. 69-79

Gene silencing of MIR22 in acute lymphoblastic leukaemia involves histone modifications independent of promoter DNA methylation

Xiaoqing Li

Xiaoqing Li

Institute of Hematology, Union Hospital, Wuhan, China

Department of Medical Microbiology and Immunology, Creighton University Medical Center, Omaha, NE

Equal contribution to this study.

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Jun Liu

Jun Liu

Institute of Hematology, Union Hospital, Wuhan, China

Department of Medical Microbiology and Immunology, Creighton University Medical Center, Omaha, NE

Equal contribution to this study.

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Rui Zhou

Rui Zhou

Department of Medical Microbiology and Immunology, Creighton University Medical Center, Omaha, NE

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Shi Huang

Shi Huang

Burnham Institute for Medical Research, La Jolla, CA, USA

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Shiang Huang

Shiang Huang

Institute of Hematology, Union Hospital, Wuhan, China

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Xian-Ming Chen

Xian-Ming Chen

Department of Medical Microbiology and Immunology, Creighton University Medical Center, Omaha, NE

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First published: 14 December 2009
Citations: 36
Shiang Huang, Institute of Hematology, Union Hospital, Wuhan, China. E-mail: [email protected];
Xian-Ming Chen, Department of Medical Microbiology and Immunology, Creighton University Medical Center, Omaha, NE 68178, USA. E-mail: [email protected]

Summary

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 indentified 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.

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