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Role of a Zn‐independent DksA in Zn homeostasis and stringent response
Author(s) -
BlabyHaas Crysten E.,
Furman Ran,
Rodionov Dmitry A.,
Artsimovitch Irina,
de CrécyLagard Valérie
Publication year - 2011
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.1365-2958.2010.07475.x
Subject(s) - biology , rna polymerase , transcription (linguistics) , zinc finger , gene , promoter , stringent response , microbiology and biotechnology , transcriptional regulation , genetics , transcription factor , escherichia coli , gene expression , linguistics , philosophy
Summary DksA is a global transcriptional regulator that directly interacts with RNA polymerase (RNAP) and, in conjunction with an alarmone ppGpp, alters transcription initiation at target promoters. DksA proteins studied to date contain a canonical Cys‐4 Zn‐finger motif thought to be essential for their proper folding and thus activity. In addition to the canonical DksA protein, the Pseudomonas aeruginosa genome encodes a closely related paralogue DksA2 that lacks the Zn‐finger motif. Here, we report that DksA2 can functionally substitute for the canonical DksA in vivo in Escherichia coli and P. aeruginosa . We also demonstrate that DksA2 affects transcription by the E. coli RNAP in vitro similarly to DksA. The dksA2 gene is positioned downstream of a putative Zur binding site. Accordingly, we show that dksA2 expression is repressed by the presence of exogenous Zn, deletion of Zur results in constitutive expression of dksA2 , and Zur binds specifically to the promoter region of dksA2 . We also found that deletion of dksA2 confers a growth defect in the absence of Zn. Our data suggest that DksA2 plays a role in Zn homeostasis and serves as a back‐up copy of the canonical Zn‐dependent DksA in Zn‐poor environments.