The transcription factor SdiA, for Suppressor of the cell division inhibitor, is possibly positively autoregulated and controls the transcription of the genes involved in cell division |CITS:|. SdiA has been shown to increase transcription from the P2 promoter of the ftsQAZ operon |CITS:| by facilitating RNA polymerase binding to the promoter region |CITS:|. SdiA activates the expression of ydiV, which is involved in the interaction between two quorum-sensing systems. An sdiA ydiV double mutant reduces cAMP levels, which inhibits quorum-sensing system 2 |CITS:|. Expression of sdiAitself is regulated by a mechanism similar to quorum sensing: exposure to conditioned medium results in a 50-80% decrease in sdiA expression |CITS:|. The transcriptional activity of SdiA is affected not only by quorum signaling but also by other environmental factors, such as oxidation |CITS:|.
Overexpression of SdiA speeds up cell division |CITS:| and causes apparently concomitant morphological changes; in both exponential and stationary phases, cells appear rounder and shorter |CITS:|. Overexpression of SdiA also leads to resistance to the DNA-damaging agent mitomycin C as well as to other drugs |CITS:|, while an sdiA null mutant strain was not hypersensitive to mitomycin C |CITS:| but was more sensitive to flouroquinolones |CITS:|.
In addition, SdiA also affects the expression of a number of genes, including a decrease in expression of several motility |CITS:| and chemotaxis |CITS:| genes, a pleiotropic effect over the expression of genes involved in cell division, drug sensitivity, DNA replication and repair, macromolecular metabolism |CITS:|, genes involved in the glutamate-dependent acid resistance systems (AR-2) |CITS:|, and an increase in the expression of the AcrAB multidrug efflux pump proteins |CITS:|.Read more >
On the other hand, SdiA is highly homologous to quorum-sensing transcription factors that belong to the LuxR family |CITS:|. The molecule inducer is represented by different N-acyl-L-homoserine lactones (AHLs), which are signaling molecules involved in communication between bacteria (quorum-sensing systems) |CITS:|. AHLs might control the transcriptional activity of SdiA by enhancing its stability rather than by directly affecting its DNA-binding affinity |CITS:|. Lee et al. showed that the transcription which SdiA mediates is controlled by indole, but whether this effect is indirect or direct is not known |CITS:|. However, it was experimentally shown that SdiA does not respond to indole, although it can inhibit SdiA activity |CITS:|. On the other hand Dyszel et al. showed that the SdiA protein is partially dependent upon a diffusible molecule [N-(3-oxo-hexanoyl)-L-homoserine lactone] |CITS:|. SdiA is regulated by an endogenous ligand, 1-octanoyl-rac-glycerol (OCL), which functions as a chemical chaperone placeholder, stabilizing SdiA and allowing for basal activity |CITS:|.
Accordingly, this family protein is composed of two domains: a conserved C-terminal domain which contains the DNA-binding region |CITS:| and the N-terminal domain, which is involved in effector binding |CITS:|.
The crystal structure of intact SdiA has been determined |CITS:|.
|Sensing class:||External sensing using transported metabolites|
|Connectivity class:||Local Regulator|
|Length:||723 bp / 240 aa|
|TU(s) encoding the TF:||
|Regulated gene(s)||ftsA, ftsQ, ftsZ, gadW, ydiV|
|Multifun term(s) of regulated gene(s)||
MultiFun Term (List of genes associated to the multifun term)
cell division (3)
ftsA, ftsQ, ftsZ
Transcription related (1)
|Regulated operon(s)||gadAXW, mraZ-rsmH-ftsLI-murEF-mraY-murD-ftsW-murGC-ddlB-ftsQAZ-lpxC, ydiV|
|First gene in the operon(s)||ftsQ, ftsQ, gadW, ydiV|
|Simple and complex regulons|
|Simple and complex regulatory phrases||
Regulatory phrase (List of promoters regulated by the phrase)
|Functional conformation||Function||Promoter||Sigma factor||Central Rel-Pos||Distance to first Gene||Genes||Sequence||LeftPos||RightPos||Evidence (Confirmed, Strong, Weak)||References|
|SdiA||repressor||ftsQp1||Sigma38||-163.5||-451.5||ftsQ, ftsA, ftsZ||
|102695||102712||[BPP], [GEA]||, |
|SdiA||repressor||ftsQp1||Sigma38||-161.5||-449.5||ftsQ, ftsA, ftsZ||
|SdiA||repressor||ftsQp1||Sigma38||-15.5||-303.5||ftsQ, ftsA, ftsZ||
|1792132||1792148||[AIBSCS], [BPP], [GEA]|||
|Evolutionary conservation of regulatory elements|
 Wang XD., de Boer PA., Rothfield LI., 1991, A factor that positively regulates cell division by activating transcription of the major cluster of essential cell division genes of Escherichia coli., EMBO J. 10(11):3363-72