Serological survey of Toxoplasma gondii infection in free-ranging Eurasian lynx (Lynx lynx) from Sweden

To investigate the prevalence of Toxoplasma gondii infection in free-ranging Eurasian lynx (Lynx lynx) in Sweden, serosanguinous fluids and feces were collected from 207 carcasses of lynx killed or found dead from 1996 to 1998. Sera were tested for antibodies against T. gondii by the direct agglutination test, and 156 (75.4%) of the sera tested positive at antibody titers>or=40. Antibody prevalence was significantly lower in lynx originating from the northern parts of Sweden than in lynx from the more southern regions that are more densely populated by humans. Age-related differences also were found, with a significantly lower prevalence (55%) in juvenile (<1-yr-old) than in subadult and adult animals (82%). There was no significant difference in seroprevalence between males and females. Oocysts typical of T. gondii were not detected in any of the fecal samples.     

Signal peptide peptidase cleavage of GB virus B core protein is required for productive infection in vivo

Chronic infection by hepatitis C virus (HCV) is a leading cause of liver disease for which better therapies are urgently needed. Because a clearer understanding of the viral life cycle may suggest novel anti-viral approaches, we studied the role of host signal peptide peptidase (SPP) in viral infection. This intramembrane protease cleaves within a C-terminal signal sequence in the viral core protein, but the molecular determinants of cleavage and whether it is required for infection in vivo are unknown. To answer these questions, we studied SPP processing in GB virus B (GBV-B) infection. GBV-B is the closest phylogenetic relative of HCV and offers an accurate surrogate model for HCV infection. We demonstrate that SPP also processes GBV-B core protein and that a serine residue in the hydrophobic region of the signal sequence (present also in HCV) is critical for efficient SPP cleavage. The small size of the serine side chain combined with its ability to form intra- and interhelical hydrogen bonds likely contributes to recognition of the signal sequence as a substrate for SPP. By introducing mutations with differing effects on SPP processing into an infectious GBV-B molecular clone, we demonstrate that SPP processing of the core protein is required for productive infection in primates. These results broaden our understanding of the mechanism and requirements for SPP cleavage and reveal a functional role in vivo for intramembrane proteolysis in host-pathogen interactions. Moreover, they identify SPP as a potential therapeutic target for reducing the impact of HCV infection.     

The plug domain of yeast Sec61p is important for efficient protein translocation, but is not essential for cell viability

The Sec61/SecY translocon mediates translocation of proteins across the membrane and integration of membrane proteins into the lipid bilayer. The structure of the translocon revealed a plug domain blocking the pore on the lumenal side. It was proposed to be important for gating the protein conducting channel and for maintaining the permeability barrier in its unoccupied state. Here, we analyzed in yeast the effect of introducing destabilizing point mutations in the plug domain or of its partial or complete deletion. Unexpectedly, even when the entire plug domain was deleted, cells were viable without growth phenotype. They showed an effect on signal sequence orientation of diagnostic signal-anchor proteins, a minor defect in cotranslational and a significant deficiency in posttranslational translocation. Steady-state levels of the mutant protein were reduced, and when coexpressed with wild-type Sec61p, the mutant lacking the plug competed poorly for complex partners. The results suggest that the plug is unlikely to be important for sealing the translocation pore in yeast but that it plays a role in stabilizing Sec61p during translocon formation.     

Phylogeny of Eunicida (Annelida) and exploring data congruence using a partition addition bootstrap alteration (PABA) approach

Even though relationships within Annelida are poorly understood, Eunicida is one of only a few major annelid lineages well supported by morphology. The seven recognized eunicid families possess sclerotized jaws that include mandibles and a maxillary apparatus. The maxillary apparatuses vary in shape and number of elements, and three main types are recognized in extant taxa: ctenognath, labidognath, and prionognath. Ctenognath jaws are usually considered to represent the plesiomorphic state of Eunicida, whereas taxa with labidognath and prionognath are thought to form a derived monophyletic assemblage. However, this hypothesis has never been tested in a statistical framework even though it holds considerable importance for understanding annelid phylogeny and possibly lophotrochozoan evolution because Eunicida has the best annelid fossil record. Therefore, we used maximum likelihood and Bayesian inference approaches to reconstruct Eunicida phylogeny using sequence data from nuclear 18S and 28S rDNA genes and mitochondrial 16S rDNA and cytochrome c oxidase subunit I genes. Additionally, we conducted three different tests to investigate suitability of combining data sets. Incongruence length difference (ILD) and Shimodaira-Hasegawa (SH) test comparisons of resultant trees under different data partitions have been widely used previously but do not give a good indication as to which nodes may be causing the conflict. Thus, we developed a partition addition bootstrap alteration (PABA) approach that evaluates congruence or conflict for any given node by determining how bootstrap scores are altered when different data partitions are added. PABA shows the contribution of each partition to the phylogeny obtained in the combined analysis. Generally, the ILD test performed worse than the other approaches in detecting incongruence. Both PABA and the SH approach indicated the 28S and COI data sets add conflicting signal, but PABA is more informative for elucidating which data partition may be misleading at a given node. All our analyses indicate that the monophyly of the labidognath/prionognath taxa and even a labidognath clade (i.e., a "Eunicidae"/Onuphidae/Lumbrineridae clade) is significantly rejected. We show that the definition of both the labidognath and ctenognath jaw type does not address adequately the variation within Eunicida and thus misleads our current evolutionary understanding. Based on the presented results a symmetric maxillary apparatus with a carrier and four to six maxillae is most likely the plesiomorphic condition for Eunicida. [COI; conflicting data; fossil record; ILD; Jaw Evolution; molecular phylogeny; rDNA; SH test.].     

Deconstructing the molecular portrait of basal-like breast cancer

Gene-expression profiling has revealed several molecular subtypes of breast cancer, which differ in their pathobiology and clinical outcomes. Basal-like tumors are a newly recognized subtype of breast cancer, which express genes that are characteristic of basal epithelial cells, such as the basal cytokeratins, and are associated with poor relapse-free and overall survival. However, the genetic and epigenetic alterations that are responsible for the biologically aggressive phenotype of these estrogen receptor-negative and HER2/ErbB2-negative tumors are not well understood, thereby hindering efforts to develop targeted therapies. Here, we focus on new insights into the molecular pathogenesis of basal-like breast cancer and explore how these discoveries might impact the treatment of these poor-prognosis tumors.