FG Synthetic Microbiology, Institute for Biotechnology, BTU Cottbus-Senftenberg, Senftenberg, Germany.
FG Molecular Microbiology, Institute for Biology, University of Hohenheim, Stuttgart, Germany.
Nucleic Acids Res. 2023 Sep 22;51(17):9452-9474. doi: 10.1093/nar/gkad675.
Prophages control their lifestyle to either be maintained within the host genome or enter the lytic cycle. Bacillus subtilis contains the SPβ prophage whose lysogenic state depends on the MrpR (YopR) protein, a key component of the lysis-lysogeny decision system. Using a historic B. subtilis strain harboring the heat-sensitive SPβ c2 mutant, we demonstrate that the lytic cycle of SPβ c2 can be induced by heat due to a single nucleotide exchange in the mrpR gene, rendering the encoded MrpRG136E protein temperature-sensitive. Structural characterization revealed that MrpR is a DNA-binding protein resembling the overall fold of tyrosine recombinases. MrpR has lost its recombinase function and the G136E exchange impairs its higher-order structure and DNA binding activity. Genome-wide profiling of MrpR binding revealed its association with the previously identified SPbeta repeated element (SPBRE) in the SPβ genome. MrpR functions as a master repressor of SPβ that binds to this conserved element to maintain lysogeny. The heat-inducible excision of the SPβ c2 mutant remains reliant on the serine recombinase SprA. A suppressor mutant analysis identified a previously unknown component of the lysis-lysogeny management system that is crucial for the induction of the lytic cycle of SPβ.
噬菌体控制其生活方式，要么在宿主基因组中维持，要么进入裂解周期。枯草芽孢杆菌含有 SPβ 噬菌体，其溶原状态取决于 MrpR（YopR）蛋白，这是裂解-溶原决策系统的关键组成部分。使用含有热敏性 SPβ c2 突变体的历史枯草芽孢杆菌菌株，我们证明 SPβ c2 的裂解周期可以通过热诱导，这是由于 mrpR 基因中的单个核苷酸交换，使编码的 MrpRG136E 蛋白对温度敏感。结构特征表明 MrpR 是一种 DNA 结合蛋白，类似于酪氨酸重组酶的整体折叠。MrpR 已经失去了其重组酶功能，G136E 交换损害了其高级结构和 DNA 结合活性。对 MrpR 结合的全基因组分析揭示了它与 SPβ 基因组中先前鉴定的 SPbeta 重复元件（SPBRE）的关联。MrpR 作为 SPβ 的主阻遏物发挥作用，与该保守元件结合以维持溶原性。SPβ c2 突变体的热诱导切除仍然依赖丝氨酸重组酶 SprA。抑制突变体分析确定了裂解-溶原管理系统中以前未知的成分，这对于诱导 SPβ 的裂解周期至关重要。
