Horino Atsuko, Kenri Tsuyoshi, Sasaki Yuko, Okamura Noboru, Sasaki Tsuguo
Laboratory of Microbiology and Immunology, Graduate School of Health Sciences, Tokyo Medical and Dental University, Tokyo 113-8519, Japan.
Department of Bacterial Pathogenesis and Infection Control, National Institute of Infectious Diseases, Musashimurayama, Tokyo 208-0011, Japan.
Microbiology (Reading). 2009 Apr;155(Pt 4):1241-1249. doi: 10.1099/mic.0.025437-0.
Mycoplasma penetrans has the ability to change its surface lipoprotein profiles frequently. The P35 family lipoproteins encoded by the mpl genes are key players in this profile variation. The M. penetrans HF-2 genome has 38 mpl genes that form three gene clusters. Most of these mpl genes have an invertible promoter sequence that is responsible for the ON/OFF switching of individual mpl gene expression. Here, we identified the recombinase that catalyses inversions of the mpl gene promoters. We focused on two open reading frames of the M. penetrans HF-2 genome, namely MYPE2900 and MYPE8180, which show significant homology to the tyrosine site-specific recombinase (Tsr) family proteins. Since genetic tools for M. penetrans are still not developed, we cloned the MYPE2900 and MYPE8180 genes and expressed them in Mycoplasma pneumoniae and Escherichia coli. The promoter regions of the mpl genes [p35 (MYPE6810) or p42 (MYPE6630) genes] were also introduced into M. pneumoniae and E. coli cells expressing MYPE2900 or MYPE8180. Inversion of these promoters occurred in the presence of the MYPE2900 gene but not in the presence of the MYPE8180 gene, indicating that the MYPE2900 gene product is the recombinase that catalyses mpl gene promoter inversions. We used a PCR-based method to detect mpl promoter inversion. This method also enabled us to detect inversions of 10 mpl gene promoters in M. penetrans HF-2 cells. All these promoter inversions occurred at the 12 bp inverted repeat (IR) sequences flanking the promoter sequence. The consensus sequence of these IRs was proposed as TAAYNNNDATTA (Y=C or T; D=A, G or T).
穿透支原体具有频繁改变其表面脂蛋白谱的能力。由mpl基因编码的P35家族脂蛋白是这种谱变化的关键因素。穿透支原体HF-2基因组有38个mpl基因，形成三个基因簇。这些mpl基因中的大多数都有一个可逆启动子序列，负责单个mpl基因表达的开/关切换。在这里，我们鉴定了催化mpl基因启动子倒位的重组酶。我们关注穿透支原体HF-2基因组的两个开放阅读框，即MYPE2900和MYPE8180，它们与酪氨酸位点特异性重组酶（Tsr）家族蛋白具有显著同源性。由于穿透支原体的遗传工具尚未开发出来，我们克隆了MYPE2900和MYPE8180基因，并在肺炎支原体和大肠杆菌中表达。mpl基因的启动子区域[p35（MYPE6810）或p42（MYPE6630）基因]也被引入表达MYPE2900或MYPE8180的肺炎支原体和大肠杆菌细胞中。这些启动子的倒位在MYPE2900基因存在的情况下发生，但在MYPE8180基因存在的情况下不发生，表明MYPE2900基因产物是催化mpl基因启动子倒位的重组酶。我们使用基于PCR的方法检测mpl启动子倒位。该方法还使我们能够检测穿透支原体HF-2细胞中10个mpl基因启动子的倒位。所有这些启动子倒位都发生在启动子序列两侧的12 bp反向重复（IR）序列处。这些IR的共有序列被提议为TAAYNNNDATTA（Y = C或T；D = A、G或T）。
