The Beclin 1 network regulates autophagy and apoptosis

Beclin 1, the mammalian orthologue of yeast Atg6, has a central role in autophagy, a process of programmed cell survival, which is increased during periods of cell stress and extinguished during the cell cycle. It interacts with several cofactors (Atg14L, UVRAG, Bif-1, Rubicon, Ambra1, HMGB1, nPIST, VMP1, SLAM, IP(3)R, PINK and survivin) to regulate the lipid kinase Vps-34 protein and promote formation of Beclin 1-Vps34-Vps15 core complexes, thereby inducing autophagy. In contrast, the BH3 domain of Beclin 1 is bound to, and inhibited by Bcl-2 or Bcl-XL. This interaction can be disrupted by phosphorylation of Bcl-2 and Beclin 1, or ubiquitination of Beclin 1. Interestingly, caspase-mediated cleavage of Beclin 1 promotes crosstalk between apoptosis and autophagy. Beclin 1 dysfunction has been implicated in many disorders, including cancer and neurodegeneration. Here, we summarize new findings regarding the organization and function of the Beclin 1 network in cellular homeostasis, focusing on the cross-regulation between apoptosis and autophagy.     

Molecular characterization of 'Bhut Jolokia' the hottest chilli

The northeast region of India, considered as 'hot spot' of biodiversity, having unique ecological environment with hot and high-humidity conditions, has given rise to the world's hottest chilli, 'Bhut Jolokia', which is at least two times hotter than Red Savina Habanero in terms of Scoville heat units (SHU). This study was undertaken to determine the distinctiveness of 'Bhut Jolokia' from Capsicum frutescens or Capsicum chinense through sequencing of the ribosomal RNA (rRNA) gene-internal transcribed ((ITS) region along with its phylogenetic analysis. Although a compensatory base change (CBC) in the ITS2 region was not observed between the closely related species of C. frutescens and C. chinense when compared with Bhut Jolokia; phylogenetic analysis using ITS1, 5.8S and ITS2 sequences indicated a distinct clade for all the accessions of 'Bhut Joloikia', while C. frutescens and C. chinense occupied discrete lineages. Further, a unique 13-base deletion was observed in all the representative accessions of 'Bhut Jolokia', making it distinct from all other members within the genus and beyond. The degree of genetic variations along with its extreme pungency might be related to ambient environmental factors of northeastern India.     

Cytokines alter target cell susceptibility to lysis. II. Evaluation of tumor infiltrating lymphocytes

We studied the susceptibility of autologous and allogeneic tumors to lysis by human tumor infiltrating lymphocytes (TIL) after pre-incubation of the tumors with human rIFN-gamma and human rTNF-alpha. Preincubation of the tumor lines with IFN-gamma or TNF enhanced susceptibility to lysis significantly; the combination of both cytokines was more effective than either alone. Pretreatment for at least 24 h was required to enhance lytic susceptibility and maximal lysis was observed after pretreatment for 48 to 72 h. Highly specific TIL lysed only their autologous tumor targets and failed to lyse cytokine pretreated allogeneic tumor cells. In TIL populations with varying specificity, cytokine pretreatment of targets enhanced autologous lysis as well as allogeneic lysis. This cytokine-mediated effect could also be observed in a lectin-dependent cytotoxicity assay and did not correlate directly with enhanced expression of MHC class I Ag or the adhesion molecules LFA-3 and ICAM-1. These results suggest that enhancement of lysis may occur at a postbinding stage by making the target cell more sensitive to the cytotoxic factors delivered by the killer cell. The fact that lysis of cytokine treated targets by cells with LAK activity was not enhanced suggests that cells with lymphokine-activated killer activity and tumor-derived T cells kill tumor targets via different mechanisms.     

Algal propagule banks modify competition, consumer and resource control on Baltic rocky shores

We hypothesized that supply from macroalgal propagule banks may influence the relative abundance of annual and perennial algae and that this may alter the effects of grazers and nutrients on species composition. In a factorial field experiment in the Baltic Sea littoral system we tested the effects of manipulating propagule banks, the abundance of crustacean and gastropod grazers, and nutrient supply on recruitment and growth of macroalgae over a year. Moreover, we determined seasonal patterns of macroalgal propagule dispersal at the experimental site and quantified algal abundance and recruitment at 25 locations throughout the Baltic Sea. Experimental manipulations had minor effects on adults of the dominating perennial alga, Fucus vesiculosus. Instead, we found that species composition was determined by processes operating at early life stages. Propagule supply from a propagule bank strongly favored the fast-growing annual alga Enteromorpha spp. which then blocked settlement and recruitment of Fucus. Grazers reduced the abundance of annual algae and indirectly favored Fucus recruitment. There was an apparent trade-off between gains from the propagule bank and losses to herbivory in five of seven colonizing species. Nutrient enrichment overrode grazer control of annual algae and accelerated the decline of Fucus only when annual algae had already achieved high densities through the propagule bank. Corroborating the experimental findings, field surveys across the Baltic showed that Fucus recruit densities can be predicted from the cover of annual algae during the period of Fucus reproduction and settlement. Recruitment inhibition by annual algae, which is driven by the abundance of annuals in the propagule bank, increasing nutrient levels, and declining consumer control, is suggested as a mechanistic explanation of the current decline of perennial algae in the Baltic Sea.     

Second-generation tetracycline-regulatable promoter: repositioned tet operator elements optimize transactivator synergy while shorter minimal promoter offers tight basal leakiness

BACKGROUND: The tetracycline-regulatable system is one of the most valuable tools for controlling gene expression. In its current form, however, the system is less than ideal for in vivo or gene therapy uses due to difficulties in set-up procedures, high basal leakiness, and unpredictable delivery and efficiency. METHODS: To address these issues, we have devised a second generation of tetracycline-regulated promoters (TREs). The second-generation TRE (SG-TRE) contains a shortened cytomegalovirus (CMV) minimal promoter together with eight tet operator sequences positioned in an optimized manner upstream of the TATA box. This construct displays far greater reduction in basal leakiness than maximal transgene expression. Conversely, maximal transgene expression is increased to a greater degree than basal leakiness by post-translational stabilization with bovine growth hormone poly A. RESULTS: In transient studies, the SG-TRE displays over 100 000-fold regulation efficiency in HeLa cells at 1:1 ratio of transactivator to reporter plasmid in the Tet-Off system. This novel promoter achieves a regulation efficiency 500- to 1000-fold higher than that of the original TRE (P(hCMV*-1)) in HeLa cells by displaying undetectable levels of basal leakiness without compromised maximal expression. In other cell lines, the SG-TRE proves to be more efficient than the original P(hCMV*-1) in a cell-dependent manner. Furthermore, the SG-TRE preserves its enhanced regulation efficiency and its reduced basal leakiness in the context of a single positive feedback regulatory vector that presents ease of delivery of the system for use in vivo. Finally, in vivo, the biological function of granulocyte-macrophage colony stimulating factor is tightly regulated in the context of SG-TRE delivered via adeno-associated viruses.     

Marine extinction risk shaped by trait–environment interactions over 500 million years

Perhaps the most pressing issue in predicting biotic responses to present and future global change is understanding how environmental factors shape the relationship between ecological traits and extinction risk. The fossil record provides millions of years of insight into how extinction selectivity (i.e., differential extinction risk) is shaped by interactions between ecological traits and environmental conditions. Numerous paleontological studies have examined trait‐based extinction selectivity; however, the extent to which these patterns are shaped by environmental conditions is poorly understood due to a lack of quantitative synthesis across studies. We conducted a meta‐analysis of published studies on fossil marine bivalves and gastropods that span 458 million years to uncover how global environmental and geochemical changes covary with trait‐based extinction selectivity. We focused on geographic range size and life habit (i.e., infaunal vs. epifaunal), two of the most important and commonly examined predictors of extinction selectivity. We used geochemical proxies related to global climate, as well as indicators of ocean acidification, to infer average global environmental conditions. Life‐habit selectivity is weakly dependent on environmental conditions, with infaunal species relatively buffered from extinction during warmer climate states. In contrast, the odds of taxa with broad geographic ranges surviving an extinction (>2500 km for genera, >500 km for species) are on average three times greater than narrow‐ranging taxa (estimate of odds ratio: 2.8, 95% confidence interval = 2.3–3.5), regardless of the prevailing global environmental conditions. The environmental independence of geographic range size extinction selectivity emphasizes the critical role of geographic range size in setting conservation priorities.