MarR-Like Transcriptional Regulator Involved in Detoxification of Aromatic Compounds in Sulfolobus solfataricus

Abstract

A DNA binding protein, BldR, was identified in the crenarchaeon Sulfolobus solfataricus as a protein 5-to 10-fold more abundant in cells grown in the presence of toxic aldehydes; it binds to regulatory sequences located upstream of an alcohol dehydrogenase gene (Sso2536). BldR is homologous to bacterial representatives of the MarR (multiple antibiotic resistance) family of transcriptional regulators that mediate response to multiple environmental stresses. Transcriptional analysis revealed that the bldR gene was transcribed in a bicistronic unit composed of the genes encoding the transcriptional regulator (Sso1352) and a putative multidrug transporter (Sso1351) upstream. By homology to bacterial counterparts, the bicistron was named the mar-like operon. The level of mar-like operon expression was found to be increased at least 10-fold in response to chemical stress by aromatic aldehydes. Under the same growth conditions, similar enhanced in vivo levels of Sso2536 gene transcript were also measured. The gene encoding BldR was expressed in E. coli, and the recombinant protein was purified to homogeneity. DNA binding assays demonstrated that the protein is indeed a transcription factor able to recognize site specifically both the Sso2536 and mar-like promoters at sites containing palindromic consensus sequences. Benzaldehyde, the substrate of ADH Ss , stimulates DNA binding of BldR at both promoters. The role of BldR in the auto-activation as well as in the regulation of the Sso2536 gene, together with results of increased operon and gene expression under conditions of exposure to aromatic aldehydes, indicates a novel coordinate regulatory mechanism in cell defense against stress by aromatic compounds.A chimeric nature of the transcription machinery with eukaryote-like basal factors and bacterium-like regulative components has been found in all members of the domain Archaea (50, 60). In fact, in most cases, homologs of bacterial regulators function in the context of the archaeal basal transcriptional apparatus, which resembles that of Eukarya (8, 26). Transcription initiation is mediated by a single RNA polymerase (RNAP) and two general transcription factors, TATA element binding protein (TBP) and transcription factor B (TFB), a homologue of the transcription factor TFIIB, which binds to the B recognition element (BRE) and determines the directionality of the transcription (7). The complex containing RNAP, TBP, and TFB is sufficient to initiate transcription in cell-free systems (31, 49), although an additional factor, transcription factor E, is required to increase transcription from some promoters (6, 29).A few homologs of eukaryal transcriptional regulators (33) and unique archaeal regulators (57) as well as non-sequencespecific DNA binding proteins (5, 30) have been investigated for their contribution to the regulation of archaeal genes.Homologs of bacterial transcriptional regulators are more common in Archaea, and representatives that have been studied experimentally include the Lrp homologs (13) that can fun...

A Transcriptional Regulator and ABC Transporters Link Stress Tolerance, (p)ppGpp, and Genetic Competence in Streptococcus mutans

“…SMu0835, which we designated rcrR for rel competence-related regulator, is predicted to encode a cytoplasmic transcriptional regulator with a winged helix-turnhelix DNA binding motif and is identified (Oralgen, Los Alamos, NM) to be a member of the multiple antibiotic resistance (MarR) family of transcriptional regulators (6). MarRtype regulators are widely distributed in bacteria and regulate many functions, including resistance to xenobiotics and oxidative stressors and expression of virulence genes (14). For example, the E. coli MarR protein modulates the expression of multiple genes that impact resistance to a variety of antibiotics and to oxidative stress (7,40).…”

Identification of an archaeal mercury regulon by chromatin immunoprecipitation

“…Three other MarR proteins of Sulfolobus have now been characterized by crystallography, and their ability to bind DNA is modulated by ligands with various affinities (Kumarevel et al, 2008). The MarR regulator BldR from S. solfataricus strain P2 is a transcriptional activator of one of the genes encoding alcohol dehydrogenase (Sso2536) and is cotranscribed with a multidrug transporter (Sso1351), presumably for the detoxification of aromatic compounds (Di Fiore et al, 2009;Fiorentino et al, 2007). BldR2 shares 35 % sequence homology with BldR and has also been characterized (Fiorentino et al, 2011).…”

Characterization of a Glutamate Transporter Operon, glnQHMP , in Streptococcus mutans and Its Role in Acid Tolerance

“…A mixture of 540 l of cell suspension, 600 l of reaction buffer (washing buffer and 1% glucose), and chloramphenicol (final concentration, 0.1 mg/ml) was incubated at 37°for 10 min. At time zero, 0.6 Ci L-[U- 14 C]glutamic acid (260 mCi/mmol) and unlabeled glutamic acid potassium salt monohydrate (final concentration, 0.1 mM) were added, and duplicate aliquots of 100 l were sampled every 2 min and immediately filtered through a 0.2-m-pore-size nitrocellulose filter. The filters were washed twice with 1 ml of ice-cold washing buffer and submerged in scintillation fluid, and the internalized radioactivity was determined with a liquid scintillation counter.…”

“…Smu.124, which may function as a transcription regulator/repressor, belongs to the MarR family. Members of this family have been shown to be involved in regulation of virulence factors, catabolism of aromatic compounds, and response to antibiotics and oxidative stress and act to prevent gene expression by sterically hindering transcription (3,14,22). Smu.124 is located upstream of four genes (Smu.127 to Smu.130) involved in the metabolism of pyruvate, which is a product of glycolysis and amino acid metabolism.…”