A novel destruction sequence targets the meiotic regulator Spo13 for anaphase-promoting complex-dependent degradation in anaphase I

The anaphase-promoting complex (APC) or cyclosome is a multisubunit ubiquitin-protein ligase that ubiquitinates and thereby promotes the destruction of the mitotic cyclins and the separase inhibitor, securin. The contributions of the APC to progression through the meiotic program are not clear. To clarify the function of the APC in meiosis, we screened several yeast meiotic proteins as APC substrates in vitro. We found that the meiotic regulator Spo13 is an APC substrate that is degraded during anaphase I. Spo13 is expressed only in meiotic cells, where it has multiple functions, including the promotion of monopolar chromosome attachment in the first division. Spo13 ubiquitination by the APC depends on an LxExxxN sequence (residues 26-32) that is distinct from previously described destruction sequences of APC substrates. Mutation of one residue, leucine 26, prevented Spo13 ubiquitination by the APC in vitro and stabilized the protein through the meiotic divisions. Analysis of meiotic progression and spore viability of yeast containing the stabilized Spo13 mutant revealed no significant defects, indicating that Spo13 destruction in anaphase I is not essential for meiosis. We propose that Spo13 destruction is one of multiple mechanisms underlying the switch from monopolar to bipolar chromosome attachment between the meiotic divisions.     

Systematic identification of SH3 domain-mediated human protein-protein interactions by peptide array target screening

Systematic identification of direct protein-protein interactions is often hampered by difficulties in expressing and purifying the corresponding full-length proteins. By taking advantage of the modular nature of many regulatory proteins, we attempted to simplify protein-protein interactions to the corresponding domain-ligand recognition and employed peptide arrays to identify such binding events. A group of 12 Src homology (SH) 3 domains from eight human proteins (Swiss-Prot ID: SRC, PLCG1, P85A, NCK1, GRB2, FYN, CRK) were used to screen a peptide target array composed of 1536 potential ligands, which led to the identification of 921 binary interactions between these proteins and 284 targets. To assess the efficiency of the peptide array target screening (PATS) method in identifying authentic protein-protein interactions, we examined a set of interactions mediated by the PLCgamma1 SH3 domain by coimmunoprecipitation and/or affinity pull-downs using full-length proteins and achieved a 75% success rate. Furthermore, we characterized a novel interaction between PLCgamma1 and hematopoietic progenitor kinase 1 (HPK1) identified by PATS and demonstrated that the PLCgamma1 SH3 domain negatively regulated HPK1 kinase activity. Compared to protein interactions listed in the online predicted human interaction protein database (OPHID), the majority of interactions identified by PATS are novel, suggesting that, when extended to the large number of peptide interaction domains encoded by the human genome, PATS should aid in the mapping of the human interactome.     

Recent developments in yeast aging

In the last decade, research into the molecular determinants of aging has progressed rapidly and much of this progress can be attributed to studies in invertebrate eukaryotic model organisms. Of these, single-celled yeast is the least complicated and most amenable to genetic and molecular manipulations. Supporting the use of this organism for aging research, increasing evidence has accumulated that a subset of pathways influencing longevity in yeast are conserved in other eukaryotes, including mammals. Here we briefly outline aging in yeast and describe recent findings that continue to keep this “simple” eukaryote at the forefront of aging research.     

Mother–embryo isotope fractionation in the pygmy devilray Mobula kuhlii cf. eregoodootenkee

We determined stable-isotope ratios for replicate muscle tissues in 13 gravid Mobula kuhlii cf. eregoodootenkee (110.4–120.4 cm disc width; W_D) and their embryos (7.0–42.3 cm W_D) and also yolks and histrotroph, to assess the potential implications for juvenile nutrition and habitat use. Irrespective of their development in the uterus, embryos had similar δ¹³C values in their muscle tissue as the mothers and both had greater values than in the histotroph. During gestation, δ¹³C values increased across all sample types. However, while embryo muscle tissue and the histotroph were associated with increasing ¹⁵N levels during embryonic development, this was depleted in the mothers’ muscle tissue and yolk. Although speculative, the observed variation in stable-isotope ratios might imply a dietary shift among gravid females during their early gestation. Irrespective of the underlying mechanisms, the results indicate neonates will have relatively greater δ¹⁵N values than post-partum females, which would probably confound juvenile foraging-ecology estimates.     

A morphological,molecular, and histopathological redescription of Henneguya nyongensis Fomena & Bouix, 1996 (Cnidaria: Myxobolidae) infecting the gills of Peter’s elephantnose fish,Gnathonemus petersii (Günther) (Osteoglossiformes: Mormyridae), imported from Nigeria

Systematic Parasitology - A Henneguya sp., morphologically resembling Henneguya nyongensis Fomena & Bouix, 1996, was isolated from the gills of Peter’s elephantnose fish, Gnathonemus...     

The role of novelty and fat and sugar concentration in food selection by captive tufted capuchins (Sapajus apella)

Capuchins, like other primates, use feedback from sensory cues and digestion to make decisions about which foods to consume and which to avoid. However, little is known about how capuchins make consumption decisions when simultaneously presented with novel and familiar foods, or how food familiarity and macronutrient concentration together influence food choice, topics with potential implications for developmental and health research. In this study, we evaluated the role of familiarity, as well as fat and sugar concentration, in the food selections of captive tufted capuchins (Sapajus apella). In the first experiment, over 10 sessions, subjects were assigned to either a group that chose between one familiar and one novel food item both high in fat or sugar (high condition), or to a group that chose between one familiar and one novel food item both low in fat or sugar (low condition). In the second experiment, subjects were divided into three groups, familiarized with food over five feeding sessions, and then offered the familiarized food and a novel food that varied in fat or sugar for 10 sessions. When offered foods high in fat, capuchins showed no clear signs of neophobia, forming an initial preference for the novel food, rejecting foods less frequently, and selecting foods faster than when offered foods low in fat. These trends were generally not observed in response to foods with sugar. When presented with options that varied in macronutrient concentration, subjects showed an initial interest in the novel food irrespective of whether it was high in fat or sugar, yet formed a final preference for the higher-concentration item. Findings suggest that the concentration of fat or sugar in novel foods may be an important mediator of exploratory behavior and that capuchins rely on immediate feedback from taste and other sensory cues to make consumption decisions.     

Pseudanthocotyloides heterocotyle (van Beneden, 1871) Euzet & Prost, 1969 (Monogenea: Polyopisthocotylea: Mazocraeidae), a parasite of herring Clupea harengus L. and sprat Sprattus sprattus L. (Teleostei: Clupeidae)

A total of 690 herring Clupea harengus L. and 88 sprat Sprattus sprattus L. caught off the west coast of Sweden, in the North Sea and off the west and south coasts of the United Kingdom, were examined for gill parasites. The monogenean Pseudanthocotyloides heterocotyle (van Beneden, 1871) Euzet & Prost, 1969 was found in 38 (5.5%) herring and one (1.1%) sprat. The parasite was significantly (P>0.05) more common off the west coast of Sweden than elsewhere and most specimens (62.5%) were found on the pseudobranchs. Only the smaller herring were infected. P. heterocotyle is redescribed and its taxonomy discussed, together with the possibility of host and parasite misidentification in previous reports.