A COMBINATION OF RNASE H (RNH) AND RECBCD OR SBCB MUTATIONS IN ESCHERICHIA-COLI K12 ADVERSELY AFFECTS GROWTH
A COMBINATION OF RNASE H (RNH) AND RECBCD OR SBCB MUTATIONS IN ESCHERICHIA-COLI K12 ADVERSELY AFFECTS GROWTH
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DOI：
10.1007/bf00273933
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发表时间：
1991-07-01
期刊：
影响因子：
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通讯作者：
CROUCH, RJ
中科院分区：
文献类型：
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作者：
ITAYA, M;CROUCH, RJ
携带rnh-339::cat突变等位基因的大肠杆菌菌落形成能力强烈依赖于recBCD和sbcB基因。使RecBCD核酸酶或核酸外切酶I （sbcB）失活的突变足以严重限制携带rnh-339::cat突变株的电镀效率。将RecBCD核酸酶的非致死性温度敏感突变recB270 （Ts）或rec271 （Ts）与rnh-339::cat结合，使菌株对生长温度敏感，即使带有recB270 （Ts）或rec271 （Ts）等位基因的rnh+菌株在42℃下存活。根据以下观察结果，可以排除RecBCD核酸酶的重组功能作为致死性来源。在rnh-339::cat菌株中引入重组精通，外切酶缺陷的recD1009等位基因或噬菌体lambda GamS蛋白（一种抑制RecBCD外切酶活性的蛋白）会显著延迟或损害这些菌株形成菌落的能力。通过包含sbcB15突变和recB21突变来恢复重组能力，recC22突变不能恢复rnh-339::cat突变株的正常平板能力。携带rnh-339::cat和sbcB15突变的recBCD+菌株在24小时后形成很少可见的菌落，但在孵育48小时后形成正常频率的菌落。最后，在rnh-339::cat菌株中引入recA56灭活RecBCD重组途径后，菌株的电镀效率不受影响。这些结果表明，rnh-339::cat recBCD菌株的生长缺陷是由于修复缺陷，而不是由recBCD或RecF途径介导的重组。
Colony forming ability of Escherichia coli strains carrying the rnh-339::cat mutant allele is strongly dependent on the recBCD and sbcB genes. A mutation inactivating either the RecBCD nuclease or exonuclease I (sbcB) is sufficient to restrict severly the efficiency of plating of strains carrying the rnh-339::cat mutation. Combining a non-lethal temperature-sensitive mutation in the RecBCD nuclease, recB270 (Ts) or recC271 (Ts), with rnh-339::cat renders strains temperature sensitive for growth, even though rnh+ strains with the recB270 (Ts) or recC271 (Ts) alleles are viable at 42-degrees-C. The recombinational functions of the RecBCD nuclease can be excluded as the source of lethality on the basis of the following observations. Introduction of a recombination proficient, exonuclease defective recD1009 allele or production of the phage lambda GamS protein (an inhibitor of the RecBCD exonuclease activity) in an rnh-339::cat strain dramatically delays or impairs the ability of such strains to form colonies. Restoration of recombination proficiency by inclusion of an sbcB15 mutation with recB21 recC22 mutations does not restore the ability of the rnh-339::cat mutant strains to plate normally. A recBCD+ strain bearing the rnh-339::cat and sbcB15 mutations forms very few visible colonies after 24 h but forms colonies at normal frequencies after 48 h of incubation. Finally, plating efficiencies of strains are unaffected when the RecBCD recombination pathway is inactivated by introduction of recA56 into an rnh-339::cat strain. These results imply that the defective growth of rnh-339::cat recBCD strains is due to a defect in repair and not recombination mediated by either the RecBCD or the RecF pathway.