Characterization of the hamster FancG/Xrcc9 gene and mutations in CHO UV40 and NM3.
The human FANCG/XRCC9 gene, which is defective in Fanconi anemia complementation group G (FA-G) cells, was first cloned by genetic complementation of the mitomycin C (MMC) sensitivity of CHO mutant UV40. The CHO NM3 mutant was subsequently assigned to the same complementation group. The parental AA8 CHO cells are hemizygous at the FancG locus, and we identified frameshift mutations that result in N-terminal truncations of the protein in both UV40 and NM3. Hypersensitivity to DNA cross-linking agents, such as MMC, typically characterizes FA cells. By introducing the native CHO FancG gene into mutant NM3, we demonstrate that hamster FancG fully corrects the 3-fold sensitivity to methyl methanesulfonate (MMS) as well as the 10-fold sensitivity to MMC, whereas resistance to ionizing radiation did not increase appreciably. In contrast, hamster cDNA transformants showed incomplete correction for both MMC and MMS sensitivity. The constitutively expressed FancG protein is present in the cytoplasmic, nuclear and chromatin fractions. FancG protein levels and subcellular localization do not change appreciably as a function of cell cycle position. Our results are consistent with roles of FancG in both the nuclear and cytoplasmic compartments to maintain genomic stability in response to various genotoxic agents.
Lamerdin
Jane E
JE
BBR Program, L441, Lawrence Livermore National Laboratory, PO Box 808, Livermore, CA 94550-0808, USA.
Yamada
Nazumi A
NA
George
James W
JW
Souza
Brian
B
Christian
Allen T
AT
Jones
Nigel J
NJ
Thompson
Larry H
LH
D000477:Alkylating Agents / Q000494:pharmacology; D000595:Amino Acid Sequence; D000818:Animals; D016466:CHO Cells; D006224:Cricetinae; D004268:DNA-Binding Proteins / Q000235:genetics*; D005199:Fanconi Anemia / Q000235:genetics; D052241:Fanconi Anemia Complementation Group G Protein; D008741:Methyl Methanesulfonate / Q000494:pharmacology; D016685:Mitomycin / Q000494:pharmacology; D008969:Molecular Sequence Data; D009153:Mutagens / Q000494:pharmacology; D009154:Mutation
D000477:Alkylating Agents; D004268:DNA-Binding Proteins; D052241:Fanconi Anemia Complementation Group G Protein; D009153:Mutagens; D016685:Mitomycin; D008741:Methyl Methanesulfonate