The LysR-Type Virulence Activator AphB Regulates the Expression of Genes in Vibrio cholerae in Response to Low pH and Anaerobiosis
The LysR-Type Virulence Activator AphB Regulates the Expression of Genes in Vibrio cholerae in Response to Low pH and Anaerobiosis
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DOI：
10.1128/jb.00193-10
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发表时间：
2010-08-01
影响因子：
3.2
通讯作者：
Skorupski, Karen
中科院分区：
文献类型：
--
作者：
Kovacikova, Gabriela;Lin, Wei;Skorupski, Karen
AphB是一种LysR型激活剂，通过与弧菌致病岛（VPI）上tcpPH启动子处的群体感应调节激活剂AphA合作，启动霍乱弧菌毒力级联的表达。为了鉴定由AphB调节的霍乱弧菌中的祖先染色体基因，我们进行了微阵列分析，并在这里显示AphB影响与VPI无关的许多基因的表达。AphB强烈激活的一个基因是cadC，其编码负责激活赖氨酸脱羧酶表达的ToxR样转录激活因子，赖氨酸脱羧酶在低pH下的存活中起重要作用。AphB激活的其他基因编码Na（+）/H（+）反向转运蛋白、碳酸酐酶、氯离子通道的ClC家族成员和Gpr 1/Fun 34/YaaH家族成员。通过凝胶迁移率变动测定，AphB通过识别启动子内的保守结合位点直接影响这些基因中的每一个。转录lacZ融合表明，AphB激活这些基因在有氧条件下的表达，以响应于低pH值，也在厌氧条件下，在中性pH值。进一步的实验表明，调节cadC由AphB响应于低pH值和厌氧是反映在异源生物大肠杆菌，是独立的全局调节Fnr和ArcAB，并且取决于包含AphB结合位点的启动子区域。这些结果提高了AphB的活性受环境pH和氧张力影响的可能性。
AphB is a LysR-type activator that initiates the expression of the virulence cascade in Vibrio cholerae by cooperating with the quorum-sensing-regulated activator AphA at the tcpPH promoter on the Vibrio pathogenicity island (VPI). To identify the ancestral chromosomal genes in V. cholerae regulated by AphB, we carried out a microarray analysis and show here that AphB influences the expression of a number of genes that are not associated with the VPI. One gene strongly activated by AphB is cadC, which encodes the ToxR-like transcriptional activator responsible for activating the expression of lysine decarboxylase, which plays an important role in survival at low pH. Other genes activated by AphB encode a Na(+)/H(+) antiporter, a carbonic anhydrase, a member of the ClC family of chloride channels, and a member of the Gpr1/Fun34/YaaH family. AphB influences each of these genes directly by recognizing a conserved binding site within their promoters, as determined by gel mobility shift assays. Transcriptional lacZ fusions indicate that AphB activates the expression of these genes under aerobic conditions in response to low pH and also under anaerobic conditions at neutral pH. Further experiments show that the regulation of cadC by AphB in response to low pH and anaerobiosis is mirrored in the heterologous organism Escherichia coli, is independent of the global regulators Fnr and ArcAB, and depends upon the region of the promoter that contains the AphB binding site. These results raise the possibility that the activity of AphB is influenced by the pH and oxygen tension of the environment.