Transcription and autoregulation of the Rv3134c-devR-devS operon of Mycobacterium tuberculosis

Abstract

DevR is a transcriptional regulator that mediates the genetic response of Mycobacterium tuberculosis to oxygen limitation and nitric oxide exposure. devR is co-transcribed along with devS, which encodes its cognate sensor kinase, and an upstream gene, Rv3134c. The transcriptional activity of this operon was characterized by primer extension, transcriptional fusion and electrophoretic mobility shift assays (EMSAs) under aerobic conditions. Transcription start points (Tsps) were detected upstream of both Rv3134c and devR, and the major transcript was derived from upstream of Rv3134c. Sequences with similarity to sigma factor consensus elements and to DevR-binding motifs were detected in the vicinity of the Tsps by in silico analysis. EMSAs with promoter regions and DevR protein showed that DevR binds to its own promoters in a sequence-specific manner with differing affinities. Consistent with the primer extension and EMSA data, Rv3134c promoters, and not devR promoters, were determined to be the principal promoters of this operon using reporter assays performed in Mycobacterium smegmatis and Escherichia coli. Furthermore, DevR modulated the activity of both devR and Rv3134c promoters. From these findings it is inferred that the Rv3134c-devR-devS operon is transcribed from multiple promoters and is autoregulated.

Unique Regulation of the DosR Regulon in the Beijing Lineage of Mycobacterium tuberculosis

“…As indicated above, we initially discounted the C507G and C601T SNPs on account of the fact that they are synonymous and are located Ͼ200 bp upstream of the dosR start codon. However, after eliminating the dosT mutation as the root cause of the Beijing constitutive DosR phenotype, we decided to look more closely at these SNPs on account of their relative proximity to the T 1 and T 2 transcription start sites (TSS) that had previously been reported for dosR (45,46). We postulated that SNPs within this same region potentially impact dosR transcription.…”

Expression of the Mycobacterium tuberculosis acr -Coregulated Genes from the DevR (DosR) Regulon Is Controlled by Multiple Levels of Regulation

“…DevR itself could be functioning as a repressor, as it has been reported to repress the activity of the Rv3134c promoter under aerobic conditions (2). Other M. tuberculosis response regulators with dual activator and repressor functions have been reported, including PhoR, which also autoregulates the expression of the phoR operon (15).…”

“…Two closely spaced TSPs have also been reported for acr, but in this case, each of two groups identified single start sites at different positions (17,31). The presence of multiple TSPs is fairly common for mycobacterial genes, but its significance is not clear (2,7,23,27,40). Different TSPs are sometimes used to differentially regulate gene expression under different growth conditions.…”

Adaptation to Environmental Stimuli within the Host: Two-Component Signal Transduction Systems of Mycobacterium tuberculosis

“…EMSAs, DNase I footprinting, and gene reporter expression studies carried out thus far generally support this contention (4, 24-26, 42, 55, 116, 125, 162). In particular, DosR recognizes a fairly conserved 18/20-bp palindromic sequence that is present with some variation upstream of the transcriptional units for these genes (Table 3) (4,25,26,42,55,116,125,162). Similar sequences are also found upstream of other genes outside this regulon, although their regulation by DosR remains unclear (116,185).…”