title: Epigenetic silencing of Bcl-2, CEBPA and p14(ARF) by the AML1-ETO oncoprotein contributing to growth arrest and differentiation block in the U937 cell line.
abstract: The AML1-ETO fusion transcription factor generated by the t(8;21) translocation is considered to deregulate the expression of genes that are crucial for normal differentiation and proliferation of hematopoietic progenitors, resulting in acute myelogenous leukemia by recruiting co-repressor complexes to DNA. To investigate the role of AML1-ETO in leukemogenesis, we transfected the cloned AML1-ETO cDNA and expressed the AML1-ETO protein in U937 myelomonocytic leukemia cells. By focusing on the anti-apoptotic gene Bcl-2, the key regulator gene of granulocytic differentiation CCAAT/enhancer-binding protein α (CEBPA) and the tumor suppressor gene p14(ARF), we found that both AML1-ETO-expressing cell lines and t(8;21) leukemia samples displayed low levels of these three genes. Chromatin immunoprecipitation assays demonstrated that Bcl-2, CEBPA and p14(ARF) were direct transcriptional targets of AML1-ETO. The universal binding of AML1-ETO to genomic DNA resulted in recruitment of methyl-CpG binding protein 2 (MeCP2), reduction of histone H3 or H4 acetylation and increased trimethylation of histone H3 lysine 9 as well as lysine 27 indicating that AML1-ETO induced heterochromatic silencing of Bcl-2, CEBPA and p14(ARF). These results suggested that the aberrant transcription factor AML1-ETO epigenetically silenced the function of the Bcl-2, CEBPA and p14(ARF) genes by inducing repressed chromatin configurations at their promoters through histone modifications.
authors.affiliation: The First Affiliated Hospital, Soochow University, Jiangsu Institute of Hematology, Key Laboratory of Thrombosis and Hemostasis, Ministry of Health, Suzhou, Jiangsu, P.R. China.
authors.forename: Wen-Yue
authors.initials: WY
authors.lastname: Zhuang
authors.forename: Jian-Nong
authors.initials: JN
authors.lastname: Cen
authors.forename: Yun
authors.initials: Y
authors.lastname: Zhao
authors.forename: Zi-Xing
authors.initials: ZX
authors.lastname: Chen
mesh_terms: D022762:CCAAT-Enhancer-Binding Proteins / Q000235:genetics*; D002454:Cell Differentiation / Q000235:genetics; D045744:Cell Line, Tumor; D049109:Cell Proliferation; D047369:Chromatin Immunoprecipitation; D050676:Core Binding Factor Alpha 2 Subunit / Q000378:metabolism*; D004268:DNA-Binding Proteins / Q000378:metabolism; D015972:Gene Expression Regulation, Neoplastic; D006801:Humans; D015479:Leukemia, Myelomonocytic, Acute / Q000235:genetics / Q000378:metabolism*; D015514:Oncogene Proteins, Fusion / Q000378:metabolism*; D019253:Proto-Oncogene Proteins c-bcl-2 / Q000235:genetics*; D000075142:RUNX1 Translocation Partner 1 Protein; D025803:Tumor Suppressor Protein p14ARF / Q000235:genetics*; D020298:U937 Cells
chemical_list: C107844:AML1-ETO fusion protein, human; D022762:CCAAT-Enhancer-Binding Proteins; C515848:CEBPA protein, human; D050676:Core Binding Factor Alpha 2 Subunit; D004268:DNA-Binding Proteins; D015514:Oncogene Proteins, Fusion; D019253:Proto-Oncogene Proteins c-bcl-2; D000075142:RUNX1 Translocation Partner 1 Protein; D025803:Tumor Suppressor Protein p14ARF