title: Role of hMLH1 in sterigmatocystin-induced G₂ phase arrest in human esophageal epithelial Het-1A cells in vitro.
abstract: Sterigmatocystin (ST), a common environmental contaminant found across the world, is generally recognized as a potential carcinogen, mutagen and teratogen. Our previous epidemiological studies suggested that ST exposure might be a risk factor for esophageal cancer. However, the direct effects of ST on human esophageal epithelial cells are currently unknown. In the present study, we examined the effect of treating a human esophageal epithelial cell line (Het-1A) with ST on DNA damage, DNA repair mechanisms, and cell cycle distribution. We found that ST treatment could induce DNA damage and lead to a G₂ phase arrest, associated with a marked up-regulation of G₂/M regulatory proteins, including Cyclin B1, Cdc2/p-Cdc2, and Cdc25C/p-Cdc25C. Additionally, we found that the expression of two mismatch repair (MMR) proteins, hMLH1 and hMSH2, was up-regulated at both the mRNA and protein levels after ST treatment, suggesting that ST could induce the MMR system in Het-1A cells. Interestingly, ST-induced G₂ phase arrest was mediated by hMLH1 up-regulation, but was independent of hMSH2. Treatment with hMLH1-siRNA prevented the up-regulation of Cyclin B1, Cdc2/p-Cdc2 and Cdc25C/p-Cdc25C in ST-treated cells, thereby inhibiting the subsequent G₂ phase arrest of Het-1A cells. Moreover, we found that hMLH1 may act as a direct sensor of ST-mediated DNA damage. In conclusion, the study demonstrated that ST caused DNA damage and triggered G₂ phase arrest in Het-1A cells, and hMLH1 participated in the ST-induced G₂ phase arrest by up-regulating G₂/M regulatory proteins.
authors.affiliation: Department of Pathology, The Second Hospital, Hebei Medical University, Shijiazhuang, China.
authors.forename: Juan
authors.initials: J
authors.lastname: Wang
authors.forename: Shujuan
authors.initials: S
authors.lastname: Huang
authors.forename: Lingxiao
authors.initials: L
authors.lastname: Xing
authors.forename: Haitao
authors.initials: H
authors.lastname: Shen
authors.forename: Xia
authors.initials: X
authors.lastname: Yan
authors.forename: Junling
authors.initials: J
authors.lastname: Wang
authors.forename: Xianghong
authors.initials: X
authors.lastname: Zhang
mesh_terms: D048868:Adaptor Proteins, Signal Transducing / Q000096:biosynthesis* / Q000235:genetics / Q000378:metabolism; D015153:Blotting, Western; D016203:CDC2 Protein Kinase; D002460:Cell Line; D020552:Comet Assay; D019926:Cyclin B / Q000096:biosynthesis / Q000235:genetics / Q000378:metabolism; D056744:Cyclin B1 / Q000096:biosynthesis / Q000235:genetics / Q000378:metabolism; D018844:Cyclin-Dependent Kinases; D004249:DNA Damage; D053843:DNA Mismatch Repair / Q000187:drug effects; D004847:Epithelial Cells / Q000187:drug effects* / Q000378:metabolism / Q000473:pathology; D004938:Esophageal Neoplasms / Q000139:chemically induced* / Q000235:genetics / Q000378:metabolism / Q000473:pathology; D005434:Flow Cytometry; D059565:G2 Phase Cell Cycle Checkpoints / Q000187:drug effects* / Q000235:genetics; D006801:Humans; D000070957:MutL Protein Homolog 1; D000070956:MutL Proteins; D009363:Neoplasm Proteins / Q000096:biosynthesis / Q000235:genetics / Q000378:metabolism; D009687:Nuclear Proteins / Q000096:biosynthesis* / Q000235:genetics / Q000378:metabolism; D034741:RNA, Small Interfering / Q000008:administration & dosage / Q000235:genetics; D060888:Real-Time Polymerase Chain Reaction; D013241:Sterigmatocystin / Q000633:toxicity*; D020687:cdc25 Phosphatases / Q000096:biosynthesis / Q000235:genetics / Q000378:metabolism
chemical_list: D048868:Adaptor Proteins, Signal Transducing; D019926:Cyclin B; D056744:Cyclin B1; C501486:MLH1 protein, human; D009363:Neoplasm Proteins; D009687:Nuclear Proteins; C088996:PMS1 protein, human; D034741:RNA, Small Interfering; D013241:Sterigmatocystin; D016203:CDC2 Protein Kinase; C528899:CDK1 protein, human; D018844:Cyclin-Dependent Kinases; C517009:CDC25C protein, human; D020687:cdc25 Phosphatases; D000070957:MutL Protein Homolog 1; D000070956:MutL Proteins