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Bacteriophage λ RexA and RexB functions assist the transition from lysogeny to lytic growth
Molecular Microbiology ( IF 2.6 ) Pub Date : 2021-08-11 , DOI: 10.1111/mmi.14792
Lynn C Thomason 1, 2 , Carl J Schiltz 3 , Carolyn Court 2 , Christopher J Hosford 3 , Myfanwy C Adams 3 , Joshua S Chappie 3 , Donald L Court 2
Affiliation  

The CI and Cro repressors of bacteriophage λ create a bistable switch between lysogenic and lytic growth. In λ lysogens, CI repressor expressed from the PRM promoter blocks expression of the lytic promoters PL and PR to allow stable maintenance of the lysogenic state. When lysogens are induced, CI repressor is inactivated and Cro repressor is expressed from the lytic PR promoter. Cro repressor blocks PRM transcription and CI repressor synthesis to ensure that the lytic state proceeds. RexA and RexB proteins, like CI, are expressed from the PRM promoter in λ lysogens; RexB is also expressed from a second promoter, PLIT, embedded in rexA. Here we show that RexA binds CI repressor and assists the transition from lysogenic to lytic growth, using both intact lysogens and defective prophages with reporter genes under the control of the lytic PL and PR promoters. Once lytic growth begins, if the bistable switch does return to the immune state, RexA expression lessens the probability that it will remain there, thus stabilizing the lytic state and activation of the lytic PL and PR promoters. RexB modulates the effect of RexA and may also help establish phage DNA replication as lytic growth ensues.

中文翻译:

噬菌体 λ RexA 和 RexB 的功能有助于从溶原性向裂解性生长的转变

噬菌体 λ 的 CI 和 Cro 阻遏物在溶原性和裂解性生长之间产生双稳态转换。在 λ 溶原菌中,从P RM启动子表达的CI 阻遏物阻断裂解启动子P LP R的表达,以稳定维持溶原状态。当溶原菌被诱导时,CI 阻遏物失活,Cro 阻遏物从裂解的 PR启动中表达出来。Cro 阻遏物阻断P RM转录和 CI 阻遏物合成,以确保裂解状态继续进行。RexA 和 RexB 蛋白,如 CI,由P RM表达λ溶原菌中的启动子;RexB 也由嵌入rexA的第二个启动子P LIT表达。在这里,我们显示 RexA 结合 CI 阻遏物并协助从溶原性向裂解生长的转变,使用完整的溶原菌和缺陷前噬菌体以及在裂解P LP R启动子控制下的报告基因。一旦裂解生长开始,如果双稳态开关确实返回到免疫状态,RexA 表达就会降低它保持在那里的可能性,从而稳定裂解状态和裂解 P L 和 P R的激活 发起人。RexB 调节 RexA 的作用,并且随着裂解生长的发生,还可能有助于建立噬菌体 DNA 复制。
更新日期:2021-08-11
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