title: Aberrant expression of the MEL1S gene identified in association with hypomethylation in adult T-cell leukemia cells.
abstract: DNA methylation plays critical roles in the development and differentiation of mammalian cells, and its dysregulation has been implicated in oncogenesis. This study was designed to determine whether DNA hypomethylation-associated aberrant gene expression is involved in adult T-cell leukemia (ATL) leukemogenesis. We isolated hypomethylated DNA regions of ATL cells compared with peripheral blood mononuclear cells from a carrier by a methylated CpG-island amplification/representational difference analysis method. The DNA regions identified contained MEL1, CACNA1H, and Nogo receptor genes. Sequencing using sodium bisulfite-treated genomic DNAs revealed the decreased methylated CpG sites, confirming that this method detected hypomethylated DNA regions. Moreover, these hypomethylated genes were aberrantly transcribed. Among them, MEL1S, an alternatively spliced form of MEL1 lacking the PR (positive regulatory domain I binding factor 1 and retinoblastoma-interacting zinc finger protein) domain, was frequently transcribed in ATL cells, and the transcriptional initiation sites were identified upstream from exons 4 and 6. Transfection of MEL1S into CTLL-2 cells conferred resistance against transforming growth factor beta (TGF-beta), suggesting that aberrant expression of MEL1S was associated with dysregulation of TGF-beta-mediated signaling. Although Tax renders cells resistant to TGF-beta, Tax could not be produced in most fresh ATL cells, in which MEL1S might be responsible for TGF-beta resistance. Our results suggest that aberrant gene expression associated with DNA hypomethylation is implicated in leukemogenesis of ATL.
authors.affiliation: Laboratory of Virus Immunology, Institute of Virus Research, Kyoto University, Kyoto, Japan.
authors.forename: Mika
authors.initials: M
authors.lastname: Yoshida
authors.forename: Kisato
authors.initials: K
authors.lastname: Nosaka
authors.forename: Jun-ichirou
authors.initials: J
authors.lastname: Yasunaga
authors.forename: Ichiro
authors.initials: I
authors.lastname: Nishikata
authors.forename: Kazuhiro
authors.initials: K
authors.lastname: Morishita
authors.forename: Masao
authors.initials: M
authors.lastname: Matsuoka
mesh_terms: D000328:Adult; D017398:Alternative Splicing / Q000235:genetics*; D020747:Calcium Channels, T-Type / Q000235:genetics; D002461:Cell Line, Transformed; D002874:Chromosome Mapping; D017931:DNA Primers; D018076:DNA, Complementary / Q000235:genetics; D004268:DNA-Binding Proteins / Q000737:chemistry / Q000235:genetics*; D058851:GPI-Linked Proteins; D015972:Gene Expression Regulation, Neoplastic / Q000235:genetics*; D015368:Human T-lymphotropic virus 1 / Q000235:genetics; D006801:Humans; D015459:Leukemia-Lymphoma, Adult T-Cell / Q000235:genetics*; D008745:Methylation; D008958:Models, Molecular; D009185:Myelin Proteins / Q000235:genetics; D000070816:Nogo Receptor 1; D016133:Polymerase Chain Reaction; D011487:Protein Conformation; D011956:Receptors, Cell Surface / Q000235:genetics; D015183:Restriction Mapping; D020133:Reverse Transcriptase Polymerase Chain Reaction / Q000379:methods; D014157:Transcription Factors / Q000737:chemistry / Q000235:genetics*; D016335:Zinc Fingers / Q000235:genetics*
chemical_list: C479952:CACNA1H protein, human; D020747:Calcium Channels, T-Type; D017931:DNA Primers; D018076:DNA, Complementary; D004268:DNA-Binding Proteins; D058851:GPI-Linked Proteins; D009185:Myelin Proteins; D000070816:Nogo Receptor 1; C416371:PRDM16 protein, human; C486580:RTN4R protein, human; D011956:Receptors, Cell Surface; D014157:Transcription Factors