title: Silencing the Metallothionein-2A gene inhibits cell cycle progression from G1- to S-phase involving ATM and cdc25A signaling in breast cancer cells.
abstract: Metallothioneins (MTs) are a group of metal-binding proteins involved in cell proliferation, differentiation and apoptosis. The MT-2A isoform is generally the most abundant isoform among the 10 known functional MT genes. In the present study, we observed that down-regulation of the MT-2A gene in MCF-7 cells via siRNA-mediated silencing inhibited cell growth by inducing cell cycle arrest in G1-phase (G1-arrest) and a marginal increase in cells in sub-G1-phase. Scanning electron microscopic examination of the cells with silenced expression of MT-2A (siMT-2A cells) revealed essentially normal cell morphology with presence of scattered apoptotic cells. To elucidate the underlying molecular mechanism, we examined the expression of cell cycle related genes in MT-2A-silenced cells and found a higher expression of the ataxia telangiectasia mutated (ATM) gene concomitant with a lower expression of the cdc25A gene. These data suggest that MT-2A could plausibly modulate cell cycle progression from G1- to S-phase via the ATM/Chk2/cdc25A pathway.
authors.affiliation: Department of Anatomy, Yong Loo Lin School of Medicine, National University of Singapore, 4 Medical Drive, Blk MD 10, S 117 597 Singapore, Singapore.
authors.forename: Daina
authors.initials: D
authors.lastname: Lim
authors.forename: Koh Mei-Xin
authors.initials: KM
authors.lastname: Jocelyn
authors.forename: George Wai-Cheong
authors.initials: GW
authors.lastname: Yip
authors.forename: Boon-Huat
authors.initials: BH
authors.lastname: Bay
mesh_terms: D064007:Ataxia Telangiectasia Mutated Proteins; D015153:Blotting, Western; D001943:Breast Neoplasms / Q000235:genetics* / Q000378:metabolism; D002453:Cell Cycle / Q000235:genetics*; D018797:Cell Cycle Proteins / Q000096:biosynthesis* / Q000235:genetics; D045744:Cell Line, Tumor; D049109:Cell Proliferation; D064447:Checkpoint Kinase 2; D004268:DNA-Binding Proteins / Q000096:biosynthesis* / Q000235:genetics; D015536:Down-Regulation; D005260:Female; D005434:Flow Cytometry; D016193:G1 Phase / Q000235:genetics; D015870:Gene Expression; D020868:Gene Silencing; D006801:Humans; D008668:Metallothionein / Q000235:genetics*; D008855:Microscopy, Electron, Scanning; D017346:Protein Serine-Threonine Kinases / Q000096:biosynthesis* / Q000235:genetics; D012333:RNA, Messenger / Q000032:analysis; D034741:RNA, Small Interfering; D020133:Reverse Transcriptase Polymerase Chain Reaction; D016196:S Phase / Q000235:genetics; D015398:Signal Transduction / Q000235:genetics*; D025521:Tumor Suppressor Proteins / Q000096:biosynthesis* / Q000235:genetics; D020687:cdc25 Phosphatases / Q000096:biosynthesis* / Q000235:genetics
chemical_list: D018797:Cell Cycle Proteins; D004268:DNA-Binding Proteins; D012333:RNA, Messenger; D034741:RNA, Small Interfering; D025521:Tumor Suppressor Proteins; D008668:Metallothionein; D064447:Checkpoint Kinase 2; C576324:ATM protein, human; D064007:Ataxia Telangiectasia Mutated Proteins; C578634:CHEK2 protein, human; D017346:Protein Serine-Threonine Kinases; C517004:CDC25A protein, human; D020687:cdc25 Phosphatases