| Project/Area Number |
62580216
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| Research Category |
Grant-in-Aid for General Scientific Research (C)
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| Allocation Type | Single-year Grants |
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| Research Field |
分子遺伝学・分子生理学
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| Research Institution | National Institute of Health |
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Principal Investigator |
SAKAKIBARA Yoshimasa National Institute of Health, Section Chief., 化学部, 室長 (10072927)
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| Project Period (FY) |
1987 – 1988
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| Project Status |
Completed (Fiscal Year 1988)
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| Budget Amount *help |
¥1,400,000 (Direct Cost: ¥1,400,000)
Fiscal Year 1988: ¥500,000 (Direct Cost: ¥500,000)
Fiscal Year 1987: ¥900,000 (Direct Cost: ¥900,000)
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| Keywords | Escherichia coli / Initiation of DNA replication / dnaR gene / DNA複製の開始 / 大腸菌のDNA複製 / dnaK遺伝子の機能 / dnaR遺伝子の機能 |
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| Research Abstract |
A novel mutation affecting DNA replication of Escherichia coli was identified at 26.3 min on the genetic map from the analysis of newly isolated temperature-sensitive mutants. Because such an allele in this locus has not been reported, the gene was designated as dnaR. The mutant was defective in both of the initiation and chain elongation at high temperature. The defect in the elongation was resumed shortly after temperature downshift if concomitant protein synthesis was permitted. However, the restoration of the initiation was rate-limiting in spite of the existence of the dnaR gene function for DNA chain elongation. The initiation subsequently took place in a synchronous manner on the cells that had been on different stages of replication cycle before temperature upshift. It could be that the dnaR gene was involved in determination of the timing of the initiation of DNA replication in cell cycle.
A newly isolated dnaK mutant was unable to initiate a new round of DNA replication at high temperature after termination of the round in progress. The cells exposed to high temperature was subsequently capable of initiating DNA replication at low temperature in a synchronous manner. In an in vitro system of oriC plasmid DNA replication, the cell extract prepared from the dnaK mutant exposed to high temperature did not display the replication activity unless purified dnaK protein was supplemented. Since the defect of the dnaK mutant in initiation of DNA replication was suppressed by the inactivation of the rnh gene as that of dnaA mutants, DnaK protein presumably functions in an early step of the initiation where DnaA protein is acting.
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