| Co-Investigator(Kenkyū-buntansha) |
NIKI Hironori National Institute of Genetics, Radiation Isotope Center, Associate Professor, 放射線・アイソトープセンター, 助教授 (70208122)
IKEDA Hideo Medinet Inc., Institute of Molecular Genetics, Director, 分子遺伝学研究所, 所長(研究職) (10012775)
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| Research Abstract |
Mechanisms of illegitimate recombination have been analyzed by newly developed assay systems for illegitimate, recombination in Escherichia coli, yeast and mouse. Based on the analyses of E. coli DNA gyrase mutants that confer a hyper-recombination phenotype, we showed that several (α-helix structures of DNA gyrase plays an important role in illegitimate recombination. It is also shown that E. coli DNA binding protein HU has an activity that suppress DNA gyrase-mediated illegitimate recombination, thus playing a regulatory role in the recombination. We also indicated that DnaB helicase, RecJ exonuclease, RecE exonuclease, RecT, RecO, RecR, RecF proteins, and DNA ligase are involved in DNA damage-induced illegitimate recombination in E. coli. Furthermore, many recombination and repair enzymes, RecQ helicase, UvrA, UvrB, MutM, Tag DNA glycosylase, AlkA DNA glycosylase, exonuclease I (SbcB), and H-NS play important roles for suppression of DNA damage-induced illegitimate recombination. We further indicated that when bacteria are grown under a starving condition, alkylated DNA lesions are spontaneously accumulated, thus leading to the promotion of DNA double-strand breaks and illegitimate recombination. In Saccharomyces cerevisiae, we showed that a DNA topoisomerase II inhibitor VP16 induces illegitimate recombination, suggesting that DNA topoisomerase II promotes illegitimate recombination through DNA double-strand break and end-joining. It is, on the other hand, shown that Sgs1 protein suppresses spontaneous illegitimate recombination. Human BLM and WRN proteins also suppressed illegitimate recombination in budding yeast. In addition, we showed that budding yeast Scc1 and fission yeast Dhp1 proteins are involved in DNA repair and chromosome segregation and that budding yeast Whip and fission yeast Mog1 and Hsk1 kinase interact with Sgs1 and Scc1, respectively. Based on these results, we proposed several models for illegitimate recombination in E. coli and yeast.
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