title: Targeted deletion of Rad9 in mouse skin keratinocytes enhances genotoxin-induced tumor development.
abstract: The Rad9 gene is evolutionarily conserved from yeast to humans and plays crucial roles in genomic maintenance, DNA repair, and cell cycle checkpoint controls. However, the function of this gene with respect to tumorigenesis is not well-understood. A Rad9-null mutation in mice causes embryonic lethality. In this study, we created mice in which mouse Rad9, Mrad9, was deleted only in keratinocytes to permit examination of the potential function of the gene in tumor development. Mice with Mrad9(+/-) or Mrad9(-/-) keratinocytes showed no overt, spontaneous morphologic defects and seemed similar to wild-type controls. Painting the carcinogen 7,12-dimethylbenzanthracene (DMBA) onto the skin of the animals caused earlier onset and more frequent formation of tumors and senile skin plaques in Mrad9(-/-) mice, compared with Mrad9(+/-) and Mrad9(+/+) littermates. DNA damage response genes p21, p53, and Mrad9B were expressed at higher levels in Mrad9(-/-) relative to Mrad9(+/+) skin. Keratinocytes isolated from Mrad9(-/-) skin had more spontaneous and DMBA-induced DNA double strand breaks than Mrad9(+/+) keratinocytes, and the levels were reduced by incubation with the antioxidant epigallocatechin gallate. These data suggest that Mrad9 plays an important role in maintaining genomic stability and preventing tumor development in keratinocytes.
authors.affiliation: National Laboratory of Biomacromolecules, Chinese Academy of Sciences, Beijing, China.
authors.forename: Zhishang
authors.initials: Z
authors.lastname: Hu
authors.forename: Yuheng
authors.initials: Y
authors.lastname: Liu
authors.forename: Chunbo
authors.initials: C
authors.lastname: Zhang
authors.forename: Yun
authors.initials: Y
authors.lastname: Zhao
authors.forename: Wei
authors.initials: W
authors.lastname: He
authors.forename: Lu
authors.initials: L
authors.lastname: Han
authors.forename: Leilei
authors.initials: L
authors.lastname: Yang
authors.forename: Kevin M
authors.initials: KM
authors.lastname: Hopkins
authors.forename: Xiao
authors.initials: X
authors.lastname: Yang
authors.forename: Howard B
authors.initials: HB
authors.lastname: Lieberman
authors.forename: Haiying
authors.initials: H
authors.lastname: Hang
mesh_terms: D015127:9,10-Dimethyl-1,2-benzanthracene; D000818:Animals; D002273:Carcinogens; D002453:Cell Cycle; D018797:Cell Cycle Proteins / Q000235:genetics* / Q000502:physiology*; D049109:Cell Proliferation; D002471:Cell Transformation, Neoplastic; D004249:DNA Damage; D017353:Gene Deletion; D015972:Gene Expression Regulation, Neoplastic; D020022:Genetic Predisposition to Disease; D015603:Keratinocytes / Q000166:cytology* / Q000378:metabolism; D051379:Mice; D009153:Mutagens / Q000378:metabolism*; D012867:Skin / Q000378:metabolism
chemical_list: D002273:Carcinogens; D018797:Cell Cycle Proteins; D009153:Mutagens; C069930:rad9 protein; D015127:9,10-Dimethyl-1,2-benzanthracene