<?xml version="1.0" encoding="UTF-8"?><xml><records><record><source-app name="Biblio" version="7.x">Drupal-Biblio</source-app><ref-type>17</ref-type><contributors><authors><author><style face="normal" font="default" size="100%">Griffith, Kevin L</style></author><author><style face="normal" font="default" size="100%">Fitzpatrick, M Megan</style></author><author><style face="normal" font="default" size="100%">Keen, Edward F</style></author><author><style face="normal" font="default" size="100%">Wolf, Richard E</style></author></authors></contributors><titles><title><style face="normal" font="default" size="100%">Two functions of the C-terminal domain of Escherichia coli Rob: mediating &quot;sequestration-dispersal&quot; as a novel off-on switch for regulating Rob's activity as a transcription activator and preventing degradation of Rob by Lon protease.</style></title><secondary-title><style face="normal" font="default" size="100%">J Mol Biol</style></secondary-title><alt-title><style face="normal" font="default" size="100%">J. Mol. Biol.</style></alt-title></titles><keywords><keyword><style  face="normal" font="default" size="100%">Decanoic Acids</style></keyword><keyword><style  face="normal" font="default" size="100%">DNA-Binding Proteins</style></keyword><keyword><style  face="normal" font="default" size="100%">Escherichia coli</style></keyword><keyword><style  face="normal" font="default" size="100%">Escherichia coli Proteins</style></keyword><keyword><style  face="normal" font="default" size="100%">Gene Expression Regulation, Bacterial</style></keyword><keyword><style  face="normal" font="default" size="100%">Genes, Reporter</style></keyword><keyword><style  face="normal" font="default" size="100%">Microscopy, Fluorescence</style></keyword><keyword><style  face="normal" font="default" size="100%">Models, Biological</style></keyword><keyword><style  face="normal" font="default" size="100%">Protease La</style></keyword><keyword><style  face="normal" font="default" size="100%">Protein Structure, Tertiary</style></keyword><keyword><style  face="normal" font="default" size="100%">Pyridines</style></keyword><keyword><style  face="normal" font="default" size="100%">Recombinant Fusion Proteins</style></keyword><keyword><style  face="normal" font="default" size="100%">Trans-Activators</style></keyword><keyword><style  face="normal" font="default" size="100%">Transcription, Genetic</style></keyword></keywords><dates><year><style  face="normal" font="default" size="100%">2009</style></year><pub-dates><date><style  face="normal" font="default" size="100%">2009 May 8</style></date></pub-dates></dates><volume><style face="normal" font="default" size="100%">388</style></volume><pages><style face="normal" font="default" size="100%">415-30</style></pages><language><style face="normal" font="default" size="100%">eng</style></language><abstract><style face="normal" font="default" size="100%">In Escherichia coli, Rob activates transcription of the SoxRS/MarA/Rob regulon. Previous work revealed that Rob resides in three to four immunostainable foci, that dipyridyl and bile salts are inducers of its activity, and that inducers bind to Rob's C-terminal domain (CTD). We propose that sequestration inactivates Rob by blocking its access to the transcriptional machinery and that inducers activate Rob by mediating its dispersal, allowing interaction with RNA polymerase. To test &quot;sequestration-dispersal&quot; as a new mechanism for regulating the activity of transcriptional activators, we fused Rob's CTD to SoxS and used indirect immunofluorescence microscopy to determine the effect of inducers on SoxS-Rob's cellular localization. Unlike native SoxS, which is uniformly distributed throughout the cell, SoxS-Rob is sequestered without an inducer, but is rapidly dispersed when cells are treated with an inducer. In this manner, Rob's CTD serves as an anti-sigma factor in regulating the co-sigma-factor-like activity of SoxS when fused to it. Rob's CTD also protects its N-terminus from Lon protease, since Lon's normally rapid degradation of SoxS is blocked in the chimera. Accordingly, Rob's CTD has novel regulatory properties that can be bestowed on another E. coli protein.</style></abstract><issue><style face="normal" font="default" size="100%">3</style></issue><custom1><style face="normal" font="default" size="100%">http://www.ncbi.nlm.nih.gov/pubmed/19289129?dopt=Abstract</style></custom1></record><record><source-app name="Biblio" version="7.x">Drupal-Biblio</source-app><ref-type>17</ref-type><contributors><authors><author><style face="normal" font="default" size="100%">Griffith, Kevin L</style></author><author><style face="normal" font="default" size="100%">Becker, Stephen M</style></author><author><style face="normal" font="default" size="100%">Wolf, Richard E</style></author></authors></contributors><titles><title><style face="normal" font="default" size="100%">Characterization of TetD as a transcriptional activator of a subset of genes of the Escherichia coli SoxS/MarA/Rob regulon.</style></title><secondary-title><style face="normal" font="default" size="100%">Mol Microbiol</style></secondary-title><alt-title><style face="normal" font="default" size="100%">Mol. Microbiol.</style></alt-title></titles><keywords><keyword><style  face="normal" font="default" size="100%">Amino Acid Sequence</style></keyword><keyword><style  face="normal" font="default" size="100%">Binding Sites</style></keyword><keyword><style  face="normal" font="default" size="100%">DNA</style></keyword><keyword><style  face="normal" font="default" size="100%">DNA-Binding Proteins</style></keyword><keyword><style  face="normal" font="default" size="100%">Escherichia coli</style></keyword><keyword><style  face="normal" font="default" size="100%">Escherichia coli Proteins</style></keyword><keyword><style  face="normal" font="default" size="100%">Gene Expression Regulation, Bacterial</style></keyword><keyword><style  face="normal" font="default" size="100%">Multigene Family</style></keyword><keyword><style  face="normal" font="default" size="100%">Promoter Regions, Genetic</style></keyword><keyword><style  face="normal" font="default" size="100%">Regulon</style></keyword><keyword><style  face="normal" font="default" size="100%">Tetracycline Resistance</style></keyword><keyword><style  face="normal" font="default" size="100%">Trans-Activators</style></keyword><keyword><style  face="normal" font="default" size="100%">Transcription Factors</style></keyword><keyword><style  face="normal" font="default" size="100%">Transcription, Genetic</style></keyword></keywords><dates><year><style  face="normal" font="default" size="100%">2005</style></year><pub-dates><date><style  face="normal" font="default" size="100%">2005 May</style></date></pub-dates></dates><volume><style face="normal" font="default" size="100%">56</style></volume><pages><style face="normal" font="default" size="100%">1103-17</style></pages><language><style face="normal" font="default" size="100%">eng</style></language><abstract><style face="normal" font="default" size="100%">In Escherichia coli, SoxS, MarA and Rob form a closely related subset of the AraC/XylS family of positive regulators, sharing approximately 42% amino acid sequence identity over the length of SoxS and the ability to activate transcription of a common set of target genes that provide resistance to redox-cycling compounds and antibiotics. On the basis of its approximately 43% amino acid sequence identity with SoxS, MarA and Rob, TetD, encoded by transposon Tn10, appears to be a fourth member of the subset. However, although its expression has been shown to be negatively regulated by TetC and not inducible by tetracycline, the physiological function of TetD is unknown. Accordingly, in the work presented here, we initiate a molecular characterization of TetD. We show that expression of TetD activates transcription of a subset of the SoxS/MarA/Rob regulon genes and confers resistance to redox-cycling compounds and antibiotics. We show that mutations in the putative TetD binding site of a TetD-activatable promoter and a mutation in the protein's N-terminal DNA recognition helix interfere with transcription activation, thereby indicating that TetD directly activates target gene transcription. Finally, we show that TetD, like SoxS and MarA, is intrinsically unstable; however, unlike SoxS and MarA, TetD is not degraded by Lon or any of the cell's known cytoplasmic ATP-dependent proteases. Thus, we conclude that TetD is a bona fide member of the SoxS/MarA/Rob subfamily of positive regulators.</style></abstract><issue><style face="normal" font="default" size="100%">4</style></issue><custom1><style face="normal" font="default" size="100%">http://www.ncbi.nlm.nih.gov/pubmed/15853893?dopt=Abstract</style></custom1></record><record><source-app name="Biblio" version="7.x">Drupal-Biblio</source-app><ref-type>17</ref-type><contributors><authors><author><style face="normal" font="default" size="100%">Griffith, Kevin L</style></author><author><style face="normal" font="default" size="100%">Shah, Ishita M</style></author><author><style face="normal" font="default" size="100%">Wolf, Richard E</style></author></authors></contributors><titles><title><style face="normal" font="default" size="100%">Proteolytic degradation of Escherichia coli transcription activators SoxS and MarA as the mechanism for reversing the induction of the superoxide (SoxRS) and multiple antibiotic resistance (Mar) regulons.</style></title><secondary-title><style face="normal" font="default" size="100%">Mol Microbiol</style></secondary-title><alt-title><style face="normal" font="default" size="100%">Mol. Microbiol.</style></alt-title></titles><keywords><keyword><style  face="normal" font="default" size="100%">Base Sequence</style></keyword><keyword><style  face="normal" font="default" size="100%">Blotting, Western</style></keyword><keyword><style  face="normal" font="default" size="100%">DNA Primers</style></keyword><keyword><style  face="normal" font="default" size="100%">DNA-Binding Proteins</style></keyword><keyword><style  face="normal" font="default" size="100%">Drug Resistance, Bacterial</style></keyword><keyword><style  face="normal" font="default" size="100%">Drug Resistance, Multiple, Bacterial</style></keyword><keyword><style  face="normal" font="default" size="100%">Endopeptidases</style></keyword><keyword><style  face="normal" font="default" size="100%">Escherichia coli</style></keyword><keyword><style  face="normal" font="default" size="100%">Escherichia coli Proteins</style></keyword><keyword><style  face="normal" font="default" size="100%">Genes, Bacterial</style></keyword><keyword><style  face="normal" font="default" size="100%">Half-Life</style></keyword><keyword><style  face="normal" font="default" size="100%">Hydrolysis</style></keyword><keyword><style  face="normal" font="default" size="100%">Kinetics</style></keyword><keyword><style  face="normal" font="default" size="100%">Mutation</style></keyword><keyword><style  face="normal" font="default" size="100%">Oxidation-Reduction</style></keyword><keyword><style  face="normal" font="default" size="100%">Promoter Regions, Genetic</style></keyword><keyword><style  face="normal" font="default" size="100%">Regulon</style></keyword><keyword><style  face="normal" font="default" size="100%">Trans-Activators</style></keyword><keyword><style  face="normal" font="default" size="100%">Transcription, Genetic</style></keyword></keywords><dates><year><style  face="normal" font="default" size="100%">2004</style></year><pub-dates><date><style  face="normal" font="default" size="100%">2004 Mar</style></date></pub-dates></dates><volume><style face="normal" font="default" size="100%">51</style></volume><pages><style face="normal" font="default" size="100%">1801-16</style></pages><language><style face="normal" font="default" size="100%">eng</style></language><abstract><style face="normal" font="default" size="100%">In Escherichia coli, the SoxRS regulon confers resistance to redox-cycling compounds, and the Mar regulon provides a defence against multiple antibiotics. The response regulators, SoxS and MarA, are synthesized de novo in response to their inducing signals and directly activate transcription of a common set of target genes. Although the mechanisms of transcription activation by SoxS and MarA have been well studied, little is known about how the systems are shut-off once the inducing stress has subsided, except that de novo synthesis of the regulators is known to cease almost immediately. Here, we induced the SoxRS regulon and determined that, upon removal of the inducer, expression of the regulon's genes quickly returns to the preinduced level. This rapid shut-off indicates that the system is reset by an active process. We found that SoxS is unstable and infer that SoxS degradation is responsible for the rapid return of the system to the ground state upon removal of the inducing signal. We also found that MarA is unstable and that the instability of both proteins is intrinsic and unregulated. We used null mutations of protease genes to identify the proteases involved in the degradation of SoxS and MarA. Among single protease mutations, only lon mutations increased the half-life of SoxS and MarA. In addition, SoxS appeared to be nearly completely stable in a lon ftsH double mutant. Using hexahistidine tags placed at the respective ends of the activators, we found that access to the amino-terminus is essential for the proteolytic degradation.</style></abstract><issue><style face="normal" font="default" size="100%">6</style></issue><custom1><style face="normal" font="default" size="100%">http://www.ncbi.nlm.nih.gov/pubmed/15009903?dopt=Abstract</style></custom1></record></records></xml>