| Budget Amount *help |
¥2,400,000 (Direct Cost: ¥2,400,000)
Fiscal Year 1999: ¥1,100,000 (Direct Cost: ¥1,100,000)
Fiscal Year 1998: ¥1,300,000 (Direct Cost: ¥1,300,000)
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| Research Abstract |
Kobayashi saw Radman and Kowalczykowski in France in 1998. Kobayashi saw Radman in USA in 1998. In 1999, Radman visited Japan and gave a lecture in the annual meeting of Biochemistry society of Japan. In 1999, Kowalczykowski visited Japan and gave a talk in 3R symposium. The following lists achievements, primarily from Kobayashi laboratory, which are most related to this collaboration.
(1) Bacterial homologous recombination in fight and collaboration with selfish restriction modification genes. Several rec genes --- recA, recBC, ruvAB, ruvC, recG --- were found to defend bacteria against the RM gene complexes by repairing cleaved chromosomes, as detected by pulsed-field gel electrophoresis. Genetic analysis indicates that the interaction of Chi sequence with RecBCD enzyme, plays an important role. In a paper published together with Kowalczykowski lab, a mutant RecBCD enzyme was shown be altered in sequence recognition in vitro.
(2) Alleviation and enhancement of type III restriction by b
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acteriophage and host homologous recombination functions. recET genes of Rac prophage and red genes of bacteriophage lambda were shown to alleviate type III restriction by EcoP1 and EcoP15. In contrast, RecBCD pathway stimulated type III restriction.
(3) Spontaneous accumulation of huge linear chromosomes in recombination-defective mutants of Escherichia coli. Huge linear forms of E.coli chromosome that are produced by spontaneous breakage of its circular forms were detected by pulsed-field gel electrophoresis in various recombination-related mutants.
(4) Why is a mismatch repair gene present? Some bacteria carry"orphan"DNA methyltransferase that is not paired with a restriction enzyme. Dcm in some strains of E.coli K-12 recognizing CC(A/T)GG provides one example. Its role has not been clear. We demonstrated that Dcm serves as molecular vaccine protecting the genome from post-segregational killing programmed by EcoRII, an RM system recognizing the same sequence.
(5) Mismatch and homologous recombination. The"random walk"model was extended to explain the effects of sequence divergence and mismatch repair system. Less
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