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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 σ H
Author(s) -
Engels Sabine,
Schweitzer JensEric,
Ludwig Carsten,
Bott Michael,
Schaffer Steffen
Publication year - 2004
Publication title -
molecular microbiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.857
H-Index - 247
eISSN - 1365-2958
pISSN - 0950-382X
DOI - 10.1111/j.1365-2958.2003.03979.x
Subject(s) - corynebacterium glutamicum , biology , gene , transcriptional regulation , operon , transcription (linguistics) , repressor , promoter , regulation of gene expression , gene expression , transcription factor , translational regulation , genetics , microbiology and biotechnology , messenger rna , escherichia coli , translation (biology) , linguistics , philosophy
Summary 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 Δ clpC 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 Δ clpC 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 σ ECF ‐dependent promoters. The ECF sigma factor σ 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 σ 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 σ H ‐dependent regulation of clpC and clpP1P2 expression appears to be conserved in other actinomycetes.