Components of DNA damage checkpoint pathway regulate UV exposure-dependent alterations of gene expression of FHIT and WWOX at chromosome fragile sites.
Common chromosome fragile sites are highly recombinogenic and susceptible to deletions during the development of environmental carcinogen-induced epithelial tumors. Previous studies showed that not only genetic but also epigenetic alterations in cancerous cells are involved in inactivation of the genes FHIT and WWOX at chromosome fragile sites, reported to be potential tumor suppressor genes. Here we investigated the effect of UV light on the gene expression. After exposure to UV, the mRNA and protein of the two genes in murine embryonic fibroblasts (MEF) were unstable, apparently at the G1-S phase of the cell cycle, which was consistent with nuclear run-on assay. A study of MEFs synchronized via a double thymidine block indicated that, after the exposure, the expression of Fhit and Wwox was reduced in E2f-1-deficient cells and markedly in wild-type cells, whereas the reduction was partially inhibited in Trp53-deficient cells; cells at the S phase seemed to be sensitive to exogenous FHIT, suggesting a role of the checkpoint at the G1-S phase in the stability of gene expression and a possible involvement of FHIT function at the S phase. The transfection experiment showed that the UV-induced decrease in expression was partially inhibited by transfection of kinase-dead Atr (ataxia telangiectasia mutated and Rad3 related), which is a sensor of UV-induced damage. Taken together, the present study showed that UV-induced alterations of the fragile site gene expression are involved at least partially in the checkpoint function, suggesting the role in the process of carcinogenesis after exposure to UV.
Ishii
Hideshi
H
Center for Molecular Medicine, Jichi Medical School, Tochigi 329-0498, Japan. hishii@ms.jichi.ac.jp
Mimori
Koshi
K
Inageta
Taeko
T
Murakumo
Yoshiki
Y
Vecchione
Andrea
A
Mori
Masaki
M
Furukawa
Yusuke
Y
D017766:Acid Anhydride Hydrolases / Q000096:biosynthesis*; D000818:Animals; D015152:Blotting, Northern; D002453:Cell Cycle; D002460:Cell Line; D002471:Cell Transformation, Neoplastic; D043283:Chromosome Fragile Sites / Q000528:radiation effects*; D002873:Chromosome Fragility; D004247:DNA / Q000528:radiation effects*; D004249:DNA Damage; D004307:Dose-Response Relationship, Radiation; D005347:Fibroblasts / Q000378:metabolism; D005434:Flow Cytometry; D016193:G1 Phase; D005786:Gene Expression Regulation / Q000528:radiation effects*; D015972:Gene Expression Regulation, Neoplastic; D016147:Genes, Tumor Suppressor; D006801:Humans; D051379:Mice; D009363:Neoplasm Proteins / Q000096:biosynthesis*; D009369:Neoplasms / Q000209:etiology; D010088:Oxidoreductases / Q000096:biosynthesis*; D012313:RNA / Q000378:metabolism; D016196:S Phase; D013997:Time Factors; D014162:Transfection; D025521:Tumor Suppressor Proteins; D014466:Ultraviolet Rays; D000074584:WW Domain-Containing Oxidoreductase; D000099170:Bis(5'-adenosyl)triphosphatase
D017766:Acid Anhydride Hydrolases; D004247:DNA; D009363:Neoplasm Proteins; D010088:Oxidoreductases; D012313:RNA; D025521:Tumor Suppressor Proteins; D000074584:WW Domain-Containing Oxidoreductase; D000099170:Bis(5'-adenosyl)triphosphatase; C486071:WWOX protein, human