Increased leukotoxin production: Characterization of 100 base pairs within the 530 base pair leukotoxin promoter region of Aggregatibacter actinomycetemcomitans
Increased leukotoxin production: Characterization of 100 base pairs within the 530 base pair leukotoxin promoter region of Aggregatibacter actinomycetemcomitans
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DOI：
10.1038/s41598-017-01692-6
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发表时间：
2017-05-15
影响因子：
4.6
通讯作者：
Fine, Daniel H.
中科院分区：
文献类型：
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作者：
Sampathkumar, Vandana;Velusamy, Senthil Kumar;Fine, Daniel H.
放线菌白细胞毒素聚集杆菌 (LtxA) 是一种主要毒力因子，可杀死白细胞，使其逃避宿主免疫监视。 A. actinomycetemcomitans 菌株可产生高水平或低水平的毒素。遗传差异存在于“所谓的 JP2”ltxA 启动子区域。这些具有 530 bp 缺失的高白细胞毒素产生菌株已被详细研究。然而，530 bp 缺失中包含的可能负责调节白细胞毒素产生的区域尚未确定。在这里，我们首次报告了 530 bp 内负责高水平 ltxA 表达的区域。我们在 A. actinomycetemcomitans 的灵长类分离株中构建了 530 bp 的缺失，其产生与 JP2 菌株相同的白细胞毒素。然后我们在跨越 530 bps 的区域中构建了连续删除。结果表明，ltxA 转录物的表达被启动子区域 298 至 397 中的潜在转录终止子降低，Delta G = -7.9 kcal/mol。我们还证实了之前的发现，即 orfX 区域和 ltxC 之间的转录融合增加了 ltxA 的表达。总之，我们构建了高产白细胞毒素的 A. actinomycetemcomitans 菌株，并鉴定了位于从 298-397 延伸的启动子区域的终止子，该终止子改变了 ltxA 的表达。
Aggregatibacter actinomycetemcomitans leukotoxin (LtxA) is a major virulence factor that kills leukocytes permitting it's escape from host immune surveillance. A. actinomycetemcomitans strains can produce high or low levels of toxin. Genetic differences reside in the "so called JP2" ltxA promoter region. These hyper-leukotoxin producing strains with the 530 bp deletion have been studied in detail. However, regions contained within the 530 bp deletion that could be responsible for modulation of leukotoxin production have not been defined. Here, we report, for the first time, on regions within the 530 bp that are responsible for high-levels of ltxA expression. We constructed a deletion of 530 bps in a primate isolate of A. actinomycetemcomitans, which produced leukotoxin equivalent to the JP2 strain. We then constructed sequential deletions in regions that span the 530 bps. Results indicated that expression of the ltxA transcript was reduced by a potential transcriptional terminator in promoter region 298 to 397 with Delta G = -7.9 kcal/mol. We also confirmed previous findings that transcriptional fusion between the orfX region and ltxC increased ltxA expression. In conclusion, we constructed a hyper-leukotoxin producing A. actinomycetemcomitans strain and identified a terminator located in the promoter region extending from 298-397 that alters ltxA expression.