ATM requirement in gene expression responses to ionizing radiation in human lymphoblasts and fibroblasts

The heritable disorder ataxia telangiectasia (AT) is caused by mutations in the AT-mutated (ATM) gene with manifestations that include predisposition to lymphoproliferative cancers and hypersensitivity to ionizing radiation (IR). We investigated gene expression changes in response to IR in human lymphoblasts and fibroblasts from seven normal and seven AT-affected individuals. Both cell types displayed ATM-dependent gene expression changes after IR, with some responses shared and some responses varying with cell type and dose. Interestingly, after 5 Gy IR, lymphoblasts displayed ATM-independent responses not seen in the fibroblasts at this dose, which likely reflect signaling through ATM-related kinases, e.g., ATR, in the absence of ATM function.     

From evil to good: a cytolysin in vaccine development

Current vaccination strategies mainly target antigens into the phagosomal, major histocompatibility complex class II antigen-processing pathway and thus lead predominantly to humoral immune responses. The elicitation of cytotoxic T-cell responses instead requires introduction of antigens into the cytosol of professional antigen-presenting cells (APCs). The intracellular bacterium Listeria monocytogenes gains access to the host cell cytosol by means of a cytolysin, listeriolysin O. Vaccine researchers have successfully employed listeriolysin in novel vaccination approaches to provide access to the cytosol of professional APCs for purified protein antigens, attenuated bacterial vaccine strains, DNA vaccines and liposome contents.     

The optional E. coli prr locus encodes a latent form of phage T4-induced anticodon nuclease.

The optional Escherichia coli prr locus restricts phage T4 mutants lacking polynucleotide kinase or RNA ligase. Underlying this restriction is the specific manifestation of the T4-induced anticodon nuclease, an enzyme which triggers the cleavage-ligation of the host tRNALys. We report here the molecular cloning, nucleotide sequence and mutational analysis of prr-associated DNA. The results indicate that prr encodes a latent form of anticodon nuclease consisting of a core enzyme and cognate masking agents. They suggest that the T4-encoded factors of anticodon nuclease counteract the prr-encoded masking agents, thus activating the latent enzyme. The encoding of a tRNA cleavage-ligation pathway by two separate genetic systems which cohabitate E. coli may provide a clue to the evolution of RNA splicing mechanisms mediated by proteins.     

Purification and characterization of perlucin and perlustrin, two new proteins from the shell of the mollusc Haliotis laevigata

Two new proteins, named perlucin and perlustrin, with M(r) 17,000 and 13,000, respectively, were isolated from the shell of the mollusc Halotis laevigata (abalone) by ion-exchange chromatography and reversed-phase HPLC after demineralization of the shell in 10% acetic acid. The sequence of the first 32 amino acids of perlucin indicated that this protein belonged to a heterogeneous group of proteins consisting of a single C-type lectin domain. Perlucin increased the precipitation of CaCO(3) from a saturated solution, indicating that it may promote the nucleation and/or the growth of CaCO(3) crystals. With pancreatic stone protein (lithostathine) and the eggshell protein ovocleidin 17, this is the third C-type lectin domain protein isolated from CaCO(3) biominerals. This indicates that this type of protein performs an important but at present unrecognized function in biomineralization. Perlustrin was a minor component of the protein mixture and the sequence of the first 33 amino acids indicated a certain similarity to part of the much larger nacre protein lustrin A.     

Bcl-2 is a monomeric protein: prevention of homodimerization by structural constraints

The pro-apoptotic activity of the Bcl-2 family member Bax has been shown to be facilitated by homodimerization. However, it is unknown whether Bcl-2 or Bcl-x(L) have to homodimerize to protect cells from apoptosis. Here we show by co-immunoprecipitation and FPLC analyses that while Bax multimerizes and forms heterodimers with Bcl-2, there is no evidence for Bcl-2 homodimerization, even in conditions under which Bcl-2 protects cells from apoptosis. Immunofluorescence studies confirmed that Bax can attract active, soluble Bcl-2 to mitochondrial membranes, but that nuclear/ER membrane-bound Bcl-2 was incapable of dislocating soluble Bcl-2. The failure of Bcl-2 to homodimerize is due to structural constraints as versions of Bcl-2 deleted or mutated in the BH1 and BH2 domains effectively dimerized with wild-type Bcl-2 and were dislocated by Bcl-2 inside cells. These data indicate that naturally occurring Bcl-2 does not expose protein domains that mediate homodimerization and therefore most likely acts as a monomer to protect cells from apoptosis.     

In vitro resistance mechanisms of Neisseria meningitidis against neutrophil extracellular traps

Neisseria meningitidis (Nm) is a leading cause of septicemia in childhood. Nm septicemia is unique with respect to very quick disease progression, high in vivo bacterial replication rate and its considerable mortality. Nm circumvents major mechanisms of innate immunity such as complement system and phagocytosis. Neutrophil extracellular traps (NETs) are formed from neutrophils during systemic infection and are suggested to contain invading microorganisms. Here, we investigated the interaction of Nm with NETs. Both, meningococci and spontaneously released outer membrane vesicles (SOMVs) were potent NET inducers. NETs were unable to kill NET bound meningococci, but slowed down their proliferation rate. Using Nm as model organism we identified three novel mechanisms how bacteria can evade NET‐mediated killing: (i) modification of lipid A of meningococcal LPS with phosphoethanolamine protected Nm from NET‐bound cathepsin G; (ii) expression of the high‐affinity zinc uptake receptor ZnuD allowed Nm to escape NET‐mediated nutritional immunity; (iii) binding of SOMVs to NETs saved Nm from NET binding and the consequent bacteriostatic effect. Escape from NETs may contribute to the most rapid progression of meningococcal disease. The induction of NET formation by Nm in vivo might aggravate thrombosis in vessels ultimately directing to disseminated intravascular coagulation (DIC).     

Native tree regeneration in native tree plantations: understanding the contribution of Araucaria angustifolia to biodiversity conservation in the threatened Atlantic Forest in Argentina

Deforestation is a global process that has strongly affected the Atlantic Forest in South America, which has been recognised as a threatened biodiversity hotspot. An important proportion of deforested areas were converted to forest plantations. Araucaria angustifolia is a native tree to the Atlantic Forest, which has been largely exploited for wood production and is currently cultivated in commercial plantations. An important question is to what extent such native tree plantations can be managed to reduce biodiversity loss in a highly diverse and vulnerable forest region . We evaluated the effect of stand age, stand basal area, as a measure of stand density, and time since last logging on the density and richness of native tree regeneration in planted araucaria stands that were successively logged over 60 years, as well as the differences between successional groups in the response of plant density to stand variables. We also compared native tree species richness in planted araucaria stands to neighbouring native forest. Species richness was 71 in the planted stands (27 ha sampled) and 82 in native forest (18 ha sampled) which approximate the range of variation in species richness found in the native forests of the study area. The total abundance and species richness of native trees increased with stand age and time since last logging, but ecological groups differed in their response to such variables. Early secondary trees increased in abundance with stand age 3–8 times faster than climax or late secondary trees. Thus, the change in species composition is expected to continue for a long term. The difference in species richness between native forest and planted stands might be mainly explained by the difference in plant density. Therefore, species richness in plantations can contribute to local native tree diversity if practices that increase native tree density are implemented.     

The effectiveness of flower strips and hedgerows on pest control,pollination services and crop yield: a quantitative synthesis

Floral plantings are promoted to foster ecological intensification of agriculture through provisioning of ecosystem services. However, a comprehensive assessment of the effectiveness of different floral plantings, their characteristics and consequences for crop yield is lacking. Here we quantified the impacts of flower strips and hedgerows on pest control (18 studies) and pollination services (17 studies) in adjacent crops in North America, Europe and New Zealand. Flower strips, but not hedgerows, enhanced pest control services in adjacent fields by 16% on average. However, effects on crop pollination and yield were more variable. Our synthesis identifies several important drivers of variability in effectiveness of plantings: pollination services declined exponentially with distance from plantings, and perennial and older flower strips with higher flowering plant diversity enhanced pollination more effectively. These findings provide promising pathways to optimise floral plantings to more effectively contribute to ecosystem service delivery and ecological intensification of agriculture in the future.