1996 Fiscal Year Final Research Report Summary
Analysis of transcriptional activation of the replication origin of Escherichia coli for initation of chromosome replication
| Project/Area Number |
07640826
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| Research Category |
Grant-in-Aid for Scientific Research (C)
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| Allocation Type | Single-year Grants |
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| Section | 一般 |
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| Research Field |
遺伝
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| Research Institution | National Insitute of Health |
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Principal Investigator |
SAKAKIBARA Yoshimasa National Institute of Health, Department of Biochemistry and Cellular Biology, Section chief., 細胞化学部, 室長 (10072927)
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| Co-Investigator(Kenkyū-buntansha) |
YAMAKAWA Yoshio National Institute of Health, Department of Biochemistry and Cellular Biology, S, 細胞化学部, 室長 (50100102)
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| Project Period (FY) |
1995 – 1996
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| Keywords | Escherichia coli / Replication initiation / RNA polymerase / Rifampicin / dnaR / dnaA / rpe / Phosphoribosylpyrophosphate synthetase |
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| Research Abstract |
Initiation of replication of Escherichia coli chromosome is rendered tempertre-sensitive by the dnaR130 mutation in the prs gene that encodes phosphoribosylpyrophosphate synthetase. The thermosensitivity of the danR mtant is supperssed by some rifampicin resistance mutations in rpoB,the gene for the beta subunit of RNA polymerase. Some of the rpoB mutations can suppress the thermosensitivity of ecrtain dnaA mutants in initiation of replication. The rpoB-mediated suppression of the dnaA or dnaR defect requires the dnaA or dnaR product to be functional in response to the rpoB mutation. Taking together with the previous finding that the dnaR defect can be suppressed by some dnaA mutations, it is likey that the dnaR product functions cooperatively with the dnaA product in a transcriptional event required for initiation of chromosome replication. The dnaR mutant exposed to the nonpermissive temperature is capable ofthermoresistant DNA synthesis in the presence of rifampicin (Rif), which inh
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ibits initiation of replication in dnaR^+ cells. The DNA synthesis elicited by Rif is initiated from oriC in a dnaA-dependent manner. It has been shown that RNA polymerase bound to Rif before attaching to template DNA loses the transcription activity while the transcibing polymerase bound to the drug continues transcription beyond some attenuators or terminators. Therefore, Rif-induced replication in the dnaR mutant seems to be mediated by particular RNA polymerase molecules that could contine transcription after Rif binding, probably through read-through transcription within or around the oriC region. As an extragenic suppressor for the dnaR mutant, the rpe gene that encodes ribulose-5-phosphate epimerase has been identified. This gene is dispensable for cell growth. Disruption of the rpe gene reverses the thermosensitivity of the dnaR mutant in DNA synthesis and cell growth. On the other hand, the rpe mutation abolishes or diminishes the abilities of certain dnaA and dnaR mutant alleles to complement dnaA and dnaR defects by different alleles, respectively. Thus, the rpe product is involved in the functions of both dnaA and dnaR products for initiation of replication of the bacterial chromosome. Less
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