Identification of a new regulator in Streptococcus pneumoniae linking quorum sensing to competence for genetic transformation
Identification of a new regulator in Streptococcus pneumoniae linking quorum sensing to competence for genetic transformation
复制标题
DOI：
10.1128/jb.181.16.5004-5016.1999
复制
发表时间：
1999-08-01
影响因子：
3.2
通讯作者：
Morrison, DA
中科院分区：
文献类型：
--
作者：
Lee, MS;Morrison, DA
肺炎链球菌的遗传转化能力受两个基因座comCDE和comAB编码的群体感应系统调控。参与DNA摄取过程和重组的另外的能力特异性操纵子cilA、cilB、cilC、cilD、cilE、cinA-recA、coiA和cfl在启动子中的-10和-25处共享不寻常的共有序列，其在comAB和comCDE的启动子中不存在。这种模式表明，一个因子调节这些转化机制基因的转录，但不参与，与comCDE和comAB的表达可能是一个替代σ因子。通过纯化肺炎球菌RNA聚合酶全酶开始了对这种全局转录调节因子的研究。在来自感受态肺炎球菌培养物的制备物中，鉴定了似乎负责cilA体外转录的蛋白质，鉴定了相应的基因tvas，并发现其以两个拷贝存在，命名为comX 1和comX 2，位于两个重复rRNA操纵子附近，转化机制操纵子的表达，如cilA，cilD，cilE和cfl，但不是群体感应操纵子comAB和comCDE的表达，被证明依赖于comX，而comX表达依赖于ComE，但不依赖于ComX本身。我们的结论是，该因子是一个能力特异性的全球转录调节剂，它将群体感应信息转导到ComE的能力，并提出它作为一个替代西格玛因素，我们还报告说，comAB和comCDE是不足以关闭的能力刺激肽诱导的基因表达，也不为随后的不应期，这表明这些现象取决于一个或多个ComX依赖的基因。
Competence for genetic transformation in Streptococcus pneumoniae is regulated by a quorum-sensing system encoded by two genetic loci, comCDE and comAB. Additional competence-specific operons, cilA, cilB, cilC, cilD, cilE, cinA-recA, coiA, and cfl involved in the DNA uptake process and recombination, share an unusual consensus sequence at -10 and -25 in the promoter, which is absent from the promoters of comAB and comCDE. This pattern suggests that a factor regulating transcription of these transformation machinery genes but not involved,vith comCDE and comAB expression might be an alternative sigma factor. A search for such a global transcriptional regulator was begun by purifying pneumococcal RNA polymerase holoenzyme, In preparations from competent pneumococcal cultures a protein which seemed to be responsible for cilA transcription in vitro was identified, The corresponding gene tvas identified and found to be present in two copies, designated comX1 and comX2, located adjacent to two of the repeated rRNA operons, Expression of transformation machinery operons, such as cilA, cilD, cilE, and cfl, but not that of the quorum-sensing operons comAB and comCDE, was shown to depend on comX, while comX expression depended on ComE but not on ComX itself. We conclude that the factor is a competence specific global transcription modulator which links quorum-sensing information transduced to ComE to competence and propose that it acts as an alternate sigma factor, We also report that comAB and comCDE are not sufficient for shutoff of competence-stimulating peptide-induced gene expression nor for the subsequent refractory period, suggesting that these phenomena depend on one or more ComX-dependent genes.