sigA (mysA, msmeg2758) gene, which codes the primary sigma factor, was used as a normalizing reference. The normalized values were referred to gene level expression of M. smegmatis as grown in 7H9 medium to mid-log phase (OD600 = 0.8). The data reveal (Figures 6A, B) that the expression of msmeg0615 and msmeg0620 is essentially similar in most of the conditions analysed. The results confirm that metal deficiency (Sauton medium, previously treated with Chelex 100) is associated with ESAT-6 cluster 3 derepression; the presence of zinc (S+Zn) has no effect on gene expression, while
iron clearly determines gene repression (S+Fe). Figure 6 Expression of msmeg0615 and msmeg0620 genes. Level of expression of msmeg0615 (A) and msmeg0620 (B) genes in differing growth this website and stress conditions INCB024360 concentration relative to the expression of the same gene in 7H9 culture in mid-log phase (OD = 0.8) (taken as 1). The level of sigA transcript was used to normalize the amount of RNA. The value represents the average and the standard deviation of three independent reactions. * indicates that values are significantly different from the control value (p < 0.01). Both genes appear to be repressed in most of the other
conditions, such as late phase of growth (OD600 = 6), nutrient starvation (PBS0 and PBS4), surface stress (SDS), ethanol stress (EtOH), oxidative stress (DA and CHP), and heat shock (42°C). Curiously, the msmeg0615 and msmeg0620 genes respond
differently to acid stress (pH 4.2), with the former induced by about 4-fold, and the latter appearing to be repressed. rv0282 and IWR-1 chemical structure rv0287 gene expression was monitored by means of qPCR to verify pH-dependent regulation in M. tuberculosis. With the sigA gene as a normalizing reference, the data revealed a higher level of expression in acid stress conditions than was the case for 7H9 standard medium with respective inductions of about 3-fold (2.97 ± 0.08) for rv0282 and 1.5-fold (1.48 ± 0.2) for rv0287. β-galactosidase activity in M. smegmatis cultures, transformed with pMYT131 derivatives carrying M. smegmatis and M. tuberculosis pr2 regions, revealed that promoter activities were SPTLC1 significantly (about two-fold) lower under acid stress than in control conditions (data not shown). Discussion ESAT-6 (early secreted antigenic target, 6 kDa) proteins, including the previously mentioned CFP-10 (10 kDa short-term culture filtrate protein), form a large family that is defined on the following base: basis of protein size (about 100 amino acids); the occurrence of the cognate genes in pairs; their location downstream of a pe and ppe gene pair, which are coding mycobacterial protein with a characteristic proline-glutamic (PE) and proline-proline-glutamic (PPE) motif.