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首页> 外文期刊>Infection and immunity >cis Elements and trans factors are both important in strain-specific regulation of the leukotoxin gene in Actinobacillus actinomycetemcomitans.
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cis Elements and trans factors are both important in strain-specific regulation of the leukotoxin gene in Actinobacillus actinomycetemcomitans.

机译：在放线放线杆菌中白细胞毒素基因的菌株特异性调节中，顺式元素和反式因子均重要。

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Actinobacillus actinomycetemcomitans, the etiologic agent of localized juvenile periodontitis, produces a potent leukotoxin that kills human neutrophils. The production of leukotoxin RNA can vary more than 50-fold among isolates of A. actinomycetemcomitans, and strains expressing high levels of leukotoxin RNA are most often found at sites of periodontal disease. To assess the relative contributions of transcription factors and promoter sequences in setting the disparate levels of leukotoxin RNA found, we have undertaken classical cis/trans analyses. First, the leukotoxin promoter regions from moderately leukotoxic (Y4) and minimally leukotoxic (ATCC 33384) strains of A. actinomycetemcomitans were cloned, sequenced, and compared with the previously sequences leukotoxin promoter region of the high-producer strain JP2. The Y4 and ATCC 33384 promoter regions each contain a 528-bp segment that is absent from JP2. Interestingly, the analysis of various deletion constructs in A. actinomycetemcomitans indicated that Y4, despite the large insertion, initiates leukotoxin RNA synthesis at the same promoter as JP2 does. To perform cis/trans analyses, these three leukotoxin promoter regions were cloned into a plasmid upstream of the reporter gene beta-galactosidase. Each plasmid was transformed into JP2, Y4, and ATCC 33384, and the beta-galactosidase levels were determined. The results indicated that the sequences responsible for down-regulating leukotoxin RNA levels in Y4 relative to JP2 are found within the transcribed region of the Y4 leukotoxin operon. Importantly, in ATCC 33384, strain-specific trans factors and promoter sequence differences are equally significant in determining the lower levels of leukotoxin RNA. We hypothesize that either strain ATCC 33384 has a negative regulatory protein (which is missing or mutated in JP2/Y4) or that JP2 and Y4 carry an activator that is missing or mutated in ATCC 33384.
机译：放线杆菌放线杆菌（Actinobacillus actinomycetemcomitans）是局部性少年牙周炎的病原体，可产生有效的白细胞毒素，杀死人的中性粒细胞。在放线放线杆菌的分离物中，白细胞毒素RNA的产生变化可以超过50倍，表达高水平白细胞毒素RNA的菌株最常见于牙周病部位。为了评估转录因子和启动子序列在设置不同水平的白细胞毒素RNA中的相对贡献，我们进行了经典的顺式/反式分析。首先，从放线放线杆菌的中度白毒性（Y4）和轻度白毒性（ATCC 33384）菌株的白细胞毒素启动子区域被克隆，测序，并与高产菌株JP2的先前序列白细胞毒素启动子区域进行比较。 Y4和ATCC 33384启动子区域各自包含JP2中不存在的528-bp片段。有趣的是，对放线放线杆菌中各种缺失构建体的分析表明，尽管插入量很大，但Y4在与JP2相同的启动子上启动白细胞毒素RNA的合成。为了进行顺式/反式分析，将这三个白细胞毒素启动子区域克隆到报告基因β-半乳糖苷酶上游的质粒中。将每个质粒转化入JP2，Y4和ATCC 33384，并确定β-半乳糖苷酶水平。结果表明，在Y4白细胞毒素操纵子的转录区域内发现了负责相对于JP2下调白细胞毒素RNA水平的序列。重要的是，在ATCC 33384中，菌株特异性反式因子和启动子序列的差异在确定较低水平的白细胞毒素RNA方面同样重要。我们假设菌株ATCC 33384具有负调控蛋白（在JP2 / Y4中缺失或突变），或者JP2和Y4携带在ATCC 33384中缺失或突变的激活剂。

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