Aminov R I, Tajima K, Ogata K, Nagamine T, Sugiura M, Benno Y
STAFF-Institute, 446-1 Ippaizuka, Kamiyiokoba, Tsukuba, Ibaraki 305, Japan.
Curr Microbiol. 1998 May;36(5):259-65. doi: 10.1007/s002849900306.
The regulation of the recA gene expression in the obligately anaerobic rumen bacterium Prevotella ruminicola was investigated by monitoring the recA-specific transcript level. P. ruminicola recA forms a monocistronic unit, but no SOS-box sequences resembling those of Escherichia coli or Bacillus subtilis can be identified upstream of the recA coding region. At the same time, we observed a fivefold increase in the level of recA mRNA in response to DNA damaging agents, mitomycin C and methyl methanesulfonate, as well as under conditions of oxidative stress. No induction was detected when growth of P. ruminicola was arrested by shifting to acidic (pH 4.8) conditions. Primer extension experiment revealed the three very close transcriptional start sites for recA. The putative -10 and -35 RNA polymerase binding regions were proposed on the basis of transcript mapping. These regions bear very little similarity to the E. coli (sigma70) and B. subtilis (sigmaA) consensus sequences, as well as to the recognition sites of other minor sigma-factors. Transcript mapping experiments in E. coli expressing P. ruminicola recA confirmed that the transcription machineries of these two bacteria recognize completely different regulatory sequences on the template to initiate transcription. Preliminary DNase I footprinting analysis data revealed that the region of imperfect dyad symmetry (AATTATAATCAATTATAAAT) found between the putative -10 region and the translation initiation codon may serve as an SOS-box-like regulatory sequence in P. ruminicola. This sequence bears no similarity to the known SOS-box sequences and, in particular, to that of E. coli and other Gram-negative bacteria.
通过监测recA特异性转录本水平，对专性厌氧瘤胃细菌普氏栖瘤胃菌（Prevotella ruminicola）中recA基因表达的调控进行了研究。普氏栖瘤胃菌recA形成一个单顺反子单元，但在recA编码区上游未发现类似于大肠杆菌或枯草芽孢杆菌的SOS盒序列。同时，我们观察到，在DNA损伤剂丝裂霉素C和甲基磺酸甲酯作用下以及氧化应激条件下，recA mRNA水平增加了五倍。当普氏栖瘤胃菌的生长通过转移至酸性（pH 4.8）条件而停止时，未检测到诱导作用。引物延伸实验揭示了recA的三个非常接近的转录起始位点。基于转录图谱提出了假定的-10和-35 RNA聚合酶结合区域。这些区域与大肠杆菌（sigma70）和枯草芽孢杆菌（sigmaA）的共有序列以及其他次要sigma因子的识别位点几乎没有相似性。在表达普氏栖瘤胃菌recA的大肠杆菌中进行的转录图谱实验证实，这两种细菌的转录机制识别模板上完全不同的调控序列来启动转录。初步的DNase I足迹分析数据表明，在假定的-10区域与翻译起始密码子之间发现的不完全二重对称区域（AATTATAATCAATTATAAAT）可能作为普氏栖瘤胃菌中类似SOS盒的调控序列。该序列与已知的SOS盒序列，特别是与大肠杆菌和其他革兰氏阴性菌的SOS盒序列没有相似性。
