Role of a Zn-independent DksA in Zn homeostasis and stringent response.
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.
Department of Microbiology and Cell Science, University of Florida, Gainesville, FL 32611, USA.
Crysten E
CE
Blaby-Haas
Ran
R
Furman
Dmitry A
DA
Rodionov
Irina
I
Artsimovitch
Valérie
V
de Crécy-Lagard
D000596:Amino Acids / Q000378:metabolism; D002614:Chelating Agents / Q000494:pharmacology; D012321:DNA-Directed RNA Polymerases / Q000235:genetics; D004926:Escherichia coli / Q000187:drug effects / Q000235:genetics / Q000378:metabolism*; D029968:Escherichia coli Proteins / Q000235:genetics / Q000302:isolation & purification / Q000378:metabolism*; D017353:Gene Deletion; D015964:Gene Expression Regulation, Bacterial / Q000187:drug effects; D006706:Homeostasis / Q000187:drug effects; D009690:Nucleic Acid Conformation; D010802:Phylogeny; D011401:Promoter Regions, Genetic / Q000235:genetics; D011485:Protein Binding / Q000187:drug effects; D055550:Protein Stability / Q000187:drug effects; D011550:Pseudomonas aeruginosa / Q000187:drug effects / Q000235:genetics; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D013054:Spectrophotometry, Atomic; D014158:Transcription, Genetic / Q000187:drug effects; D015032:Zinc / Q000378:metabolism*
D000596:Amino Acids; D002614:Chelating Agents; D029968:Escherichia coli Proteins; D012333:RNA, Messenger; C090751:dksA protein, E coli; D012321:DNA-Directed RNA Polymerases; D015032:Zinc
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