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Enzymology of DNA Repair in the radiation‐resistant extremophile Deinococcus radiodurans
Author(s) -
Cao Zheng,
Shadrick William R,
Julin Douglas
Publication year - 2009
Publication title -
the faseb journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.709
H-Index - 277
eISSN - 1530-6860
pISSN - 0892-6638
DOI - 10.1096/fasebj.23.1_supplement.836.11
Subject(s) - deinococcus radiodurans , helicase , homologous recombination , dna repair , biology , gene , dna , genetics , deinococcus , genome , recbcd , microbiology and biotechnology , rna
The bacterium Deinococcus radiodurans exhibits extraordinary resistance to the effects of ionizing radiation, and other genotoxic agents. We are using genetic and biochemical approaches to define the enzymatic pathways by which D. radiodurans repairs DNA damage. D. radiodurans genome loci DR1902 (RecD) and DR1572 (the putative helD gene) encode DNA helicases. Cells with a helD deletion are more sensitive than wild‐type to hydrogen peroxide and methyl‐methanesulfonate, but they are not sensitive to gamma or UV irradiation. Both helicases have a protein domain that is homologous to other superfamily 1 helicases, and an additional N‐terminal domain. The N‐terminal domain of HelD is essential for DNA unwinding by this enzyme. We are attempting to purify the helicase domain of RecD as defined by limited proteolysis, and to examine the kinetics of DNA unwinding by the domain and the full‐length RecD protein. Genome locus DR1126 encodes RecJ, a single‐strand‐specific exonuclease in the RecF pathway for DNA recombination and repair in E. coli . We have deleted the gene from the D. radiodurans genome by standard homologous recombination techniques. We are unable to delete the gene from each of the ~10 chromosomal copies in the cell, suggesting that recJ may be an essential gene. Cells carrying the partial deletion are more sensitive to UV irradiation than wild‐type, suggesting an important role for RecJ in D. radiodurans .