Mitochondrial copy number and risk of breast cancer: A pilot study

It has been proposed that the copy number of mitochondria DNA (mtDNA) per cell reflects gene–environment interactions between unknown hereditary factors and exposures affecting levels of oxidative stress. However, whether copy number of mtDNA could be a risk predictor of oxidative stress-related human cancers, such as breast cancer, remains to be determined. To explore the role of mtDNA copy number in breast cancer etiology, we analyzed mtDNA copy number in whole blood from 103 patients with breast cancer and 103 matched control subjects and examined in relation to endogenous antioxidants. Case patients with breast cancer had a statistically significantly higher mtDNA copy number than control subjects (median: 1.29 vs. 0.80, P < 0.01). High mtDNA copy number (above the median in controls) was associated with a statistically significantly increased risk of breast cancer, compared with low copy number (Odds ratio (OR) = 4.67, 95% CI: 2.45–8.92), with a statistically significant dose–response relationship in trend analysis (P < 0.01). Moreover, mtDNA copy number was significantly inversely associated with several important endogenous oxidants and antioxidants in blood in either the cases (total glutathione, CuZn-SOD activity and myeloperoxidase (MPO)) or the controls (catalase (CAT) activity). These results suggest the mtDNA copy number could be associated with risk of breast cancer, perhaps through an oxidative stress mechanism.     

Matrix metalloproteinases: Expression,regulation and role in the immunopathology of tuberculosis

Mycobacterium tuberculosis (Mtb) leads to approximately 1.5 million human deaths every year. In pulmonary tuberculosis (TB), Mtb must drive host tissue destruction to cause pulmonary cavitation and dissemination in the tissues. Matrix metalloproteinases (MMPs) are endopeptidases capable of degrading all components of pulmonary extracellular matrix (ECM). It is well established that Mtb infection leads to upregulation of MMPs and also causes disturbance in the balance between MMPs and tissue inhibitors of metalloproteinases (TIMPs), thus altering the extracellular matrix deposition. In TB, secretion of MMPs is mainly regulated by NF‐κB, p38 and MAPK signalling pathways. In addition, recent studies have demonstrated the immunomodulatory roles of MMPs in Mtb pathogenesis. Researchers have proposed a new regimen of improved TB treatment by inhibition of MMP activity to hinder matrix destruction and to minimize the TB‐associated morbidity and mortality. The proposed regimen involves adjunctive use of MMP inhibitors such as doxycycline, marimastat and other related drugs along with front‐line anti‐TB drugs to reduce granuloma formation and bacterial load. These findings implicate the possible addition of economical and well‐tolerated MMP inhibitors to current multidrug regimens as an attractive mean to increase the drug potency. Here, we will summarize the recent advancements regarding expression of MMPs in TB, their immunomodulatory role, as well as their potential as therapeutic targets to control the deadly disease.     

Antibiotic resistance and extended spectrum beta-lactamases: Types,epidemiology and treatment

Antibiotic resistance is a problem of deep scientific concern both in hospital and community settings. Rapid detection in clinical laboratories is essential for the judicious recognition of antimicrobial resistant organisms. Production of extended-spectrum β-lactamases (ESBLs) is a significant resistance-mechanism that impedes the antimicrobial treatment of infections caused by Enterobacteriaceae and is a serious threat to the currently available antibiotic armory. ESBLs are classified into several groups according to their amino acid sequence homology. Proper infection control practices and barriers are essential to prevent spread and outbreaks of ESBL producing bacteria. As bacteria have developed different strategies to counter the effects of antibiotics, the identification of the resistance mechanism may help in the discovery and design of new antimicrobial agents. The carbapenems are widely regarded as the drugs of choice for the treatment of severe infections caused by ESBL-producing Enterobacteriaceae, although comparative clinical trials are scarce. Hence, more expeditious diagnostic testing of ESBL-producing bacteria and the feasible modification of guidelines for community-onset bacteremia associated with different infections are prescribed.     

L-Tryptophan-dependent biosynthesis of indole-3-acetic acid (IAA) improves plant growth and colonization of maize by <Emphasis Type="BoldItalic">Burkholderia phytofirmans</Emphasis> PsJN

Burkholderia phytofirmans PsJN is a well-known plant growth-promoting bacterium that establishes rhizospheric and endophytic colonization in different plants. PsJN inoculation promotes growth of different horticultural crops. L-Tryptophan (L-TRP) application may further improve its effectiveness, due to substrate (L-TRP)-dependent inoculum (PsJN)-derived auxins in the rhizosphere. In the present study, the substrate (L-TRP)-dependent response of PsJN inoculation to maize growth and auxin biosynthesis was evaluated under pot conditions. In vitro auxin biosynthesis by PsJN was determined in the absence and presence of L-TRP, a physiological precursor of auxins. Surface-disinfected seeds were treated with peat-based inoculum and L-TRP solutions (10^?4 and 10^?5 M). Results revealed that L-TRP application and PsJN inoculation, when applied separately, significantly increased the growth parameters of maize compared to untreated control. However, PsJN inoculation supplemented with L-TRP (10^?5 M) gave the most promising results and significantly increased plant height, photosynthesis, chlorophyll content, root biomass and shoot biomass up to 18, 16, 45, 62 and 55 %, respectively, compared to the uninoculated control. Similarly, higher values of N, P and IAA content were observed with precursor (L-TRP)–inoculum (PsJN) interaction. The inoculant strain efficiently colonized maize seedlings and was recovered from the rhizosphere, root and shoot of plants. The results imply that substrate (L-TRP)-derived IAA biosynthesis in the rhizosphere by PsJN inoculation could be a useful approach for improving the growth, photosynthesis and nutrient content of maize plants.     

Biophysical basis of the binding of WWOX tumor suppressor to WBP1 and WBP2 adaptors

The WW-containing oxidoreductase (WWOX) tumor suppressor participates in a diverse array of cellular activities by virtue of its ability to recognize WW-binding protein 1 (WBP1) and WW-binding protein 2 (WBP2) signaling adaptors among a wide variety of other ligands. Herein, using a multitude of biophysical techniques, we provide evidence that while the WW1 domain of WWOX binds to PPXY motifs within WBP1 and WBP2 in a physiologically relevant manner, the WW2 domain exhibits no affinity toward any of these PPXY motifs. Importantly, our data suggest that while R25/W44 residues located within the binding pocket of a triple-stranded β-fold of WW1 domain are critical for the recognition of PPXY ligands, they are replaced by the chemically distinct E66/Y85 duo at structurally equivalent positions within the WW2 domain, thereby accounting for its failure to bind PPXY ligands. Predictably, not only does the introduction of E66R/Y85W double substitution within the WW2 domain result in gain of function but the resulting engineered domain, hereinafter referred to as WW2_RW, also appears to be a much stronger binding partner of WBP1 and WBP2 than the wild-type WW1 domain. We also show that while the WW1 domain is structurally disordered and folds upon ligand binding, the WW2 domain not only adopts a fully structured conformation but also aids stabilization and ligand binding to WW1 domain. This salient observation implies that the WW2 domain likely serves as a chaperone to augment the physiological function of WW1 domain within WWOX. Collectively, our study lays the groundwork for understanding the molecular basis of a key protein-protein interaction pertinent to human health and disease.     

Complete Genome Sequence of Mycobacterium fortuitum subsp. fortuitum Type Strain DSM46621

Mycobacterium fortuitum is a member of the rapidly growing nontuberculous mycobacteria (NTM). It is ubiquitous in water and soil habitats, including hospital environments. M. fortuitum is increasingly recognized as an opportunistic nosocomial pathogen causing disseminated infection. Here we report the genome sequence of M. fortuitum subsp. fortuitum type strain DSM46621.     

Mechanistic basis for RAG discrimination between recombination sites and the off-target sites of human lymphomas

During V(D)J recombination, RAG targeting to correct sites versus off-target sites relies on both DNA sequence features and on chromatin marks. Kinetic analysis using the first highly active full-length purified RAG1/RAG2 complexes has now allowed us to define the important catalytic features of this complex. We found that the overall rate of nicking, but not hairpinning, is critical for the discrimination between correct (optimal) versus off-target (suboptimal) sites used in human T-cell lymphomas, and we show that the C-terminal portion of RAG2 is required for this. This type of kinetic analysis permits us to analyze only the catalytically active RAG complex, in contrast to all other methods, which are unavoidably confounded by mixture with inactive RAG complexes. Moreover, we can distinguish the two major features of any enzymatic catalysis: the binding constant (K(D)) and the catalytic turnover rate, k(cat). Beyond a minimal essential threshold of heptamer quality, further suboptimal heptamer deviations primarily reduce the catalytic rate constant k(cat) for nicking. Suboptimal nonamers reduce not only the binding of the RAG complex to the recombination site (K(D)) but also the catalytic rate constant, consistent with a tight interaction between the RAG complex and substrate during catalysis. These features explain many aspects of RAG physiology and pathophysiology.