Morikawa Kazuya, Inose Yumiko, Okamura Hideyuki, Maruyama Atsushi, Hayashi Hideo, Takeyasu Kunio, Ohta Toshiko
Institute of Basic Medical Sciences, University of Tsukuba, Tsukuba, 305-8577 Japan.
Genes Cells. 2003 Aug;8(8):699-712. doi: 10.1046/j.1365-2443.2003.00668.x.
Staphylococcus aureus is a major human pathogen and causes a serious hospital infection due to the acquired multidrug resistance. Unlike the well-studied bacteria such as Escherichia coli and Bacillus subtilis, which have seven and 18 sigma factors, respectively, only two sigma factors have been known for S. aureus. We searched for possible sigma factor genes by examining the S. aureus genome with a special attention to the gene arrangement around the sigma factor genes of a close relative, B. subtilis.
A new sigma factor gene was identified in Staphylococcus. The gene constituted a conserved gene cluster with other genes including translation- and transcription-related genes. Phylogenetic analysis and comparison of the gene sequences among species indicated that the staphylococcal sigma factor originated from a common ancestor of B. subtilis SigH. An over-expression of this sigma factor in S. aureus resulted in a drastic induction of the expression of the com operons that encode proteins required for the natural genetic competence.
We demonstrated that the newly identified staphylococcal sigma factor participated in a regulatory network of transcription that controlled the genetic competence genes. In our phylogenetic tree, the factor was classified as a single group with a common function.
金黄色葡萄球菌是一种主要的人类病原体，由于获得性多重耐药性而导致严重的医院感染。与研究充分的细菌如大肠杆菌和枯草芽孢杆菌不同，它们分别有7个和18个σ因子，而金黄色葡萄球菌仅已知有两个σ因子。我们通过检查金黄色葡萄球菌基因组来寻找可能的σ因子基因，特别关注其近亲枯草芽孢杆菌的σ因子基因周围的基因排列。
在葡萄球菌中鉴定出一个新的σ因子基因。该基因与包括翻译和转录相关基因在内的其他基因构成一个保守的基因簇。系统发育分析和物种间基因序列比较表明，葡萄球菌的σ因子起源于枯草芽孢杆菌SigH的共同祖先。该σ因子在金黄色葡萄球菌中的过表达导致编码自然遗传转化所需蛋白质的com操纵子的表达急剧诱导。
我们证明新鉴定的葡萄球菌σ因子参与了控制遗传转化基因的转录调控网络。在我们的系统发育树中，该因子被归类为具有共同功能的单一组。
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