Ryder L, Sharples G J, Lloyd R G
Department of Genetics, University of Nottingham, Queens Medical Centre, United Kingdom.
Genetics. 1996 Jul;143(3):1101-14. doi: 10.1093/genetics/143.3.1101.
Analysis of the aroLM-sbcCD interval of the Escherichia coli K-12 chromosome revealed a new gene (rdgC) encoding a function required for growth in recombination-deficient recBC sbcBC strains. Deletion of rdgC does not reduce viability, conjugational recombination, or DNA repair in rec+, recA, recB, recF, or recJ mutants. However, it makes the growth of recBC sbcBC strains reliant on the RecA, RecF, and RuvC proteins and, to a large extent, on RuvAB. The recBC sbcBC delta rdgC ruvAB construct forms colonies, but cell viability is reduced to < 5%. A recBC sbcBC delta rdgC derivative carrying the temperature-sensitive recA200 allele grows at 32 degrees but not 42 degrees. Multicopy rdgC+ plasmids reduce the growth rate of recBC sbcBC strains, while multicopy sbcC+ plasmids that reactivate SbcCD nuclease cannot be maintained without RdgC protein. The data presented are interpreted to suggest that exonuclease-depleted recBC sbcBC strains have difficulty removing the displaced arm of a collapsed replication fork and that this problem is compounded in the absence of RdgC. Recombination then becomes necessary to repair the fork and allow chromosome duplication to be completed. The possibility that RdgC is an exonuclease is discussed.
对大肠杆菌K-12染色体的aroLM-sbcCD区间进行分析，发现了一个新基因（rdgC），其编码在重组缺陷型recBC sbcBC菌株中生长所需的一种功能。在rec⁺、recA、recB、recF或recJ突变体中，rdgC的缺失不会降低生存能力、接合重组或DNA修复能力。然而，它使recBC sbcBC菌株的生长依赖于RecA、RecF和RuvC蛋白，并且在很大程度上依赖于RuvAB。recBC sbcBC ΔrdgC ruvAB构建体能够形成菌落，但细胞生存能力降至<5%。携带温度敏感型recA200等位基因的recBC sbcBC ΔrdgC衍生物在32℃时生长，但在42℃时不生长。多拷贝的rdgC⁺质粒会降低recBC sbcBC菌株的生长速率，而重新激活SbcCD核酸酶的多拷贝sbcC⁺质粒在没有RdgC蛋白的情况下无法维持。所呈现的数据被解释为表明核酸外切酶缺失的recBC sbcBC菌株在去除坍塌复制叉的置换臂时存在困难，并且在没有RdgC的情况下这个问题会更加严重。然后重组对于修复复制叉并完成染色体复制变得必要。文中还讨论了RdgC是一种核酸外切酶的可能性。
