clpC and clpP1P2 gene expression in Corynebacterium glutamicum is controlled by a regulatory network involving the transcriptional regulators ClgR and HspR as well as the ECF sigma factor σH
clpC and clpP1P2 gene expression in Corynebacterium glutamicum is controlled by a regulatory network involving the transcriptional regulators ClgR and HspR as well as the ECF sigma factor σH
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DOI：
10.1111/j.1365-2958.2003.03979.x
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发表时间：
2004-04-01
影响因子：
3.6
通讯作者：
Schaffer, S
中科院分区：
文献类型：
--
作者：
Engels, S;Schweitzer, JE;Schaffer, S
ATP依赖性蛋白酶Clp在细胞的蛋白质质量控制系统和细胞过程的调节中起重要作用。在谷氨酸棒杆菌中，蛋白水解亚基ClpP1和ClpP2以及相应mRNA的水平在缺失编码Clp ATP酶亚基的clpC基因后急剧增加。我们确定了一个调节蛋白，命名为ClgR，结合到一个共同的回文序列基序在前面的clpP1P2以及clpC。DeltaclpC背景中clgR的缺失完全消除了两种操纵子的转录增加，表明ClgR激活这些基因的转录。ClgR活性本身可能通过其稳定性的ClpC依赖性调节来控制，因为ClgR仅存在于DeltaclpC中而不存在于野生型细胞中，而ClgR mRNA的水平在两种菌株中是相当的。clpC、clpP1P2和clgR的表达在严重的热应激时被诱导，然而，独立于ClgR。在这些基因前面的热响应转录起始位点的鉴定揭示了典型的西格玛（ECF）依赖性启动子的序列基序的存在。ECF σ因子σ（H）可以被鉴定为响应严重热应激的clpC、clpP1P2和clgR的转录激活所需。在clgR前面的第二个热响应性但σ（H）非依赖性启动子可以被鉴定为受到转录阻遏物HspR的负调控。综上所述，这些结果表明，clpC和clpP1P2在C.谷氨酸通过独立的和分级组织的途径进行复杂的调节，允许多种环境刺激的整合。clpC和clpP1P2表达的ClgR和sigma（H）依赖性调节似乎在其他放线菌中是保守的。
The ATP-dependent protease Clp plays important roles in the cell's protein quality control system and in the regulation of cellular processes. In Corynebacterium glutamicum, the levels of the proteolytic subunits ClpP1 and ClpP2 as well as of the corresponding mRNAs were drastically increased upon deletion of the clpC gene, coding for a Clp ATPase subunit. We identified a regulatory protein, designated ClgR, binding to a common palindromic sequence motif in front of clpP1P2 as well as of clpC. Deletion of clgR in the DeltaclpC background completely abolished the increased transcription of both operons, indicating that ClgR activates transcription of these genes. ClgR activity itself is probably controlled via ClpC-dependent regulation of its stability, as ClgR is only present in DeltaclpC and not in wild-type cells, whereas the levels of clgR mRNA are comparable in both strains. clpC, clpP1P2 and clgR expression is induced upon severe heat stress, however, independently of ClgR. Identification of the heat-responsive transcriptional start sites in front of these genes revealed the presence of sequence motifs typical for sigma(ECF)-dependent promoters. The ECF sigma factor sigma(H) could be identified as being required for transcriptional activation of clpC, clpP1P2 and clgR in response to severe heat stress. A second heat-responsive but sigma(H)-independent promoter in front of clgR could be identified that is subject to negative regulation by the transcriptional repressor HspR. Taken together, these results show that clpC and clpP1P2 expression in C. glutamicum is subject to complex regulation via both independent and hierarchically organized pathways, allowing for the integration of multiple environmental stimuli. Both the ClgR- and sigma(H)-dependent regulation of clpC and clpP1P2 expression appears to be conserved in other actinomycetes.