Characterization of Genes Regulated Directly by the VirR/VirS System in Clostridium perfringens
Characterization of Genes Regulated Directly by the VirR/VirS System in Clostridium perfringens
复制标题
DOI：
10.1128/jb.01573-07
复制
发表时间：
2008-12-01
影响因子：
3.2
通讯作者：
Shimizu, Tohru
中科院分区：
文献类型：
--
作者：
Okumura, Kayo;Ohtani, Kaori;Shimizu, Tohru
对产气荚膜梭菌菌株13的基因组的完整序列的分析导致鉴定了五个基因，包括pfoA（编码θ毒素）和vrr（编码VirR/VirS调节的RNA），其具有开放阅读框（ORF）上游的共有VirR结合序列，表明这些基因的表达可能直接由双组分VirR/VirS系统调节。为了测试这种可能性，我们研究了VirR/VirS系统介导的三个基因的转录调控，virT，ccp（编码α-梭菌蛋白酶），和维鲁，与新的VirR结合序列。北方分析显示，virT、ccp和维鲁mRNA的稳态水平（RNA表达量的增加或减少）在virR突变株中低于野生型菌株，pfoA和vrr转录物的水平也是如此。一致VirR结合位点相对于virT、ccp和维鲁启动子中的转录起始位点类似地定位。virT和维鲁的突变和过表达分析显示，virT基因产物对pfoA和ccp的表达具有负面影响，而维鲁基因产物对pfoA、virT、ccp和vrr的表达具有正面影响。virT或维鲁推定ORF中的无义突变和移码突变不影响调节功能，表明virT和维鲁可能编码RNA调节因子而不是蛋白质。这些结果表明，一个复杂的调控网络，可能涉及几个调控RNA分子，支配的VirR/VirS调节子在C。产气荚膜杆菌
Analysis of the complete sequence of the genome of Clostridium perfringens strain 13 resulted in identification of five genes, including pfoA (encoding theta toxin) and vrr (encoding VirR/VirS-regulated RNA), with consensus VirR-binding sequences upstream of the open reading frame (ORF), suggesting that expression of these genes may be regulated directly by the two-component VirR/VirS system. To test this possibility, we examined VirR/VirS system-mediated transcriptional regulation of three genes, virT, ccp (encoding alpha-clostripain), and virU, with the novel VirR-binding sequences. Northern analysis revealed that the steady-state levels (increases or decreases in the amounts of RNA expressed) of virT, ccp, and virU mRNAs were lower in a virR mutant strain than in the wild-type strain, as were the levels of the pfoA and vrr transcripts. The consensus VirR-binding sites were located similarly relative to the transcription start sites in the virT, ccp, and virU promoters. Mutation and overexpression analyses with virT and virU revealed that the virT gene product has a negative effect on expression of pfoA and ccp, whereas the virU gene product positively affects expression of pfoA, virT, ccp, and vrr. Nonsense and frameshift mutations in the virT or virU putative ORF did not affect the regulatory functions, suggesting that virT and virU may encode RNA regulators rather than proteins. These results suggest that a complex regulatory network, perhaps involving several regulatory RNA molecules, governs the expression of the VirR/VirS regulon in C. perfringens.