Inter-subunit recognition and manifestation of segmental mobility in Escherichia coli RNA polymerase: a case study with omega-beta' interaction

Omega (omega), consisting of 91 amino acids, is the smallest of all the Escherichia coli RNA polymerase subunits and is organized into an N-terminal domain of 53 amino acids followed by an unstructured tail in the C-terminal region. Our earlier experiments have shown a chaperone-like function of omega in which it helps to maintain beta' in a correct conformation and recruit it to the alpha(2)beta subassembly to form a functional core enzyme (alpha(2)betabeta'omega). The X-ray structure analysis of Thermus aquaticus core RNA polymerase suggests that two regions of omega latch onto the N-terminal and C-terminal ends of the beta'-subunit. In the present study we have monitored the conformational changes in beta' as the denatured protein is refolded in the presence and absence of omega using tryptophan fluorescence emission of beta' as well as acrylamide quenching of Trp fluorescence. Results indicate that the presence of stoichiometric amounts of omega is helpful in beta' refolding. We have also monitored the behavior of the C-terminal tail of omega by engineering three cysteine residues at three different sites in omega and subsequently labeling them with a sulphydryl-specific fluorescent probe. Fluorescence anisotropy measurements of the labeled protein indicate that the C-terminal domain of omega is mobile in the free protein and gets restrained in the presence of beta'. Calculations on side-chain interactions show that out of the three mutated positions, two have near neighbourhood interactions only with side-chains in the beta' subunit whereas the end of the C-terminal of omega, although it is restrained in the presence of beta', has no interacting partner within a 4-A radius.     

The additional 165 amino acids in the B protein of Escherichia coli DNA gyrase have an important role in DNA binding

DNA gyrase is the only enzyme known to negatively supercoil DNA. The enzyme is a heterotetramer of A(2)B(2) subunit composition. Alignment of the primary sequence of gyrase B (GyrB) from various species shows that they can be grouped into two classes. The GyrB of Gram-negative eubacteria has a stretch of about 165 amino acids in the C-terminal half, which is lacking in other GyrB subunits and type II topoisomerases. In Escherichia coli, no function has so far been attributed to this stretch. In this study, we have tried to assess the function of this region both in vivo and in vitro. A deletant (GyrBDelta160) lacking this region is non-functional in vivo. The holoenzyme reconstituted from gyrase A (GyrA) and GyrBDelta160 shows reduced but detectable supercoiling and quinolone-induced cleavage activity in vitro. GyrBDelta160 retains its ability to bind to GyrA and novobiocin. However, when reconstituted with GyrA, the deletant shows greatly impaired DNA binding. The intrinsic ATPase activity of the GyrBDelta160 is comparable to that of wild type GyrB, but this activity is not stimulated by DNA. These studies indicate that the additional stretch present in GyrB is essential for the DNA binding ability of E. coli gyrase.     

Lifetime prevalence of mental disorders in Lebanon: first onset, treatment, and exposure to war

Background

There are no published data on national lifetime prevalence and treatment of mental disorders in the Arab region. Furthermore, the effect of war on first onset of disorders has not been addressed previously on a national level, especially in the Arab region. Thus, the current study aims at investigating the lifetime prevalence, treatment, age of onset of mental disorders, and their relationship to war in Lebanon.

Methods and Findings

The Lebanese Evaluation of the Burden of Ailments and Needs Of the Nation study was carried out on a nationally representative sample of the Lebanese population (n = 2,857 adults). Respondents were interviewed using the fully structured WHO Composite International Diagnostic Interview 3.0. Lifetime prevalence of any Diagnostic and Statistical Manual of Mental Disorders, fourth edition (DSM-IV) disorder was 25.8%. Anxiety (16.7%) and mood (12.6%) were more common than impulse control (4.4%) and substance (2.2%) disorders. Only a minority of people with any mental disorder ever received professional treatment, with substantial delays (6 to 28 y) between the onset of disorders and onset of treatment. War exposure increased the risk of first onset of anxiety (odds ratio [OR] 5.92, 95% confidence interval [CI] 2.5–14.1), mood (OR 3.32, 95% CI 2.0–5.6), and impulse control disorders (OR 12.72, 95% CI 4.5–35.7).

Conclusions

About one-fourth of the sample (25.8%) met criteria for at least one of the DSM-IV disorders at some point in their lives. There is a substantial unmet need for early identification and treatment. Exposure to war events increases the odds of first onset of mental disorders.     

Contemporary Updates on the Physiology of Glucagon like Peptide-1 and Its Agonist to Treat Type 2 Diabetes Mellitus

Pathogenesis of diabetes mellitus involves scores of different factors, out of which Glucagon like factor-1 (GLP-1) plays a foremost role. GLP-1 is a pepti     

The Mycobacterial MsDps2 Protein Is a Nucleoid-Forming DNA Binding Protein Regulated by Sigma Factors σA and σB

The Dps (DNA-binding protein from starved cells) proteins from Mycobacterium smegmatis MsDps1 and MsDps2 are both DNA-binding proteins with some differences. While MsDps1 has two oligomeric states, with one of them responsible for DNA binding, MsDps2 has only one DNA-binding oligomeric state. Both the proteins however, show iron-binding activity. The MsDps1 protein has been shown previously to be induced under conditions of starvation and osmotic stress and is regulated by the extra cellular sigma factors σ^H and σ^F. We show here, that the second Dps homologue in M. smegmatis, namely MsDps2, is purified in a DNA-bound form and exhibits nucleoid-like structures under the atomic force microscope. It appears that the N-terminal sequence of Dps2 plays a role in nucleoid formation. MsDps2, unlike MsDps1, does not show elevated expression in nutritionally starved or stationary phase conditions; rather its promoter is recognized by RNA polymerase containing σ^A or σ^B, under in vitro conditions. We propose that due to the nucleoid-condensing ability, the expression of MsDps2 is tightly regulated inside the cells.     

Comparative assessment of in situ bioremediation potential of cadmium resistant acidophilic Pseudomonas putida 62BN and alkalophilic Pseudomonas monteilli 97AN strains on soybean

A study was undertaken to examine the effects of the acidophilic strain 62BN (pH 5.5) and alkalophilic strain 97AN (pH 9.0) on remediation of cadmium and their subsequent effects on soybean (Glycine max var. PS-1347) in acidic and alkaline soils, respectively. The effect of cadmium on soybean plants was studied in acidic (pH 6.3 ± 0.2) and alkaline (8.5 ± 0.2) soil amended with 124 μM CdCl₂ concentration, respectively, and the cadmium toxicity was evident from stunted growth, poor rooting, and cadmium accumulation in each case. Furthermore, 16S ribosomal DNA (rDNA) sequencing identified 62BN as a Pseudomonas putida strain and 97AN as a Pseudomonas monteilli strain. In situ studies showed that on seed bacterization, both the P. putida 62BN strain and P. monteilli 97AN strain were able to enhance plant growth in terms of agronomical parameters, in the presence of cadmium in acidic and alkaline soils, respectively. Apart from this, strain 62BN and 97AN reduced cadmium concentration in plant and soil significantly (p < 0.05) in their respective soil types. Further comparative analysis revealed that P. putida 62BN was more effective than P. monteilli 97AN strain in remediation of cadmium. The bacterial strains offer promise as inoculants to improve the growth of plants in the presence of toxic Cd concentrations in the environment with their optimum pH.     

Epigenetic regulator MLL2 shows altered expression in cancer cell lines and tumors from human breast and colon

Background  

MLL2, an epigenetic regulator in mammalian cells, mediates histone 3 lysine 4 tri-methylation (H3K4me3) through the formation of a multiprotein complex. MLL2 shares a high degree of structural similarity with MLL, which is frequently disrupted in leukemias via chromosomal translocations. However, this structural similarity is not accompanied by functional equivalence. In light of this difference, and previous reports on involvement of epigenetic regulators in malignancies, we investigated MLL2 expression in established cell lines from breast and colon tissues. We then investigated MLL2 in solid tumors of breast and colon by immunohistochemistry, and evaluated potential associations with established clinicopathologic variables.