Center for Microbial Pathogenesis, The Research Institute at Nationwide Children's Hospital, Columbus, Ohio, USA.
Department of Medicinal Chemistry and Pharmacognosy, Center for Biomolecular Sciences, University of Illinois at Chicago, Chicago, Illinois, USA.
Sci Rep. 2018 Nov 8;8(1):16535. doi: 10.1038/s41598-018-34816-7.
Horizontal gene transfer is an important means of bacterial evolution. This includes natural genetic transformation, where bacterial cells become "competent" and DNA is acquired from the extracellular environment. Natural competence in many species of Streptococcus, is regulated by quorum sensing via the ComRS receptor-signal pair. The ComR-XIP (mature ComS peptide) complex induces expression of the alternative sigma factor SigX, which targets RNA polymerase to CIN-box promoters to activate genes involved in DNA uptake and recombination. In addition, the widely distributed Streptococcus prophage gene paratox (prx) also contains a CIN-box, and here we demonstrate it to be transcriptionally activated by XIP. In vitro experiments demonstrate that Prx binds ComR directly and prevents the ComR-XIP complex from interacting with DNA. Mutations of prx in vivo caused increased expression of the late competence gene ssb when induced with XIP as compared to wild-type, and Prx orthologues are able to inhibit ComR activation by XIP in a reporter strain which lacks an endogenous prx. Additionally, an X-ray crystal structure of Prx reveals a unique fold that implies a novel molecular mechanism to inhibit ComR. Overall, our results suggest Prx functions to inhibit the acquisition of new DNA by Streptococcus.
水平基因转移是细菌进化的重要手段。这包括自然遗传转化，其中细菌细胞变得“有能力”，并从细胞外环境中获得 DNA。许多链球菌物种的自然能力受群体感应通过 ComRS 受体-信号对调节。ComR-XIP（成熟的 ComS 肽）复合物诱导替代 sigma 因子 SigX 的表达，该因子将 RNA 聚合酶靶向 CIN-box 启动子，以激活参与 DNA 摄取和重组的基因。此外，广泛分布的链球菌噬菌体基因 paratox (prx) 也含有 CIN-box，我们在这里证明它可被 XIP 转录激活。体外实验表明，Prx 可直接结合 ComR 并阻止 ComR-XIP 复合物与 DNA 相互作用。与野生型相比，体内 prx 突变导致 XIP 诱导时晚期能力基因 ssb 的表达增加，并且 Prx 同源物能够抑制缺乏内源性 prx 的报告菌株中 XIP 对 ComR 的激活。此外，Prx 的 X 射线晶体结构揭示了一种独特的折叠，暗示了一种抑制 ComR 的新分子机制。总的来说，我们的结果表明 Prx 可抑制链球菌获取新的 DNA。
