Actin participates in the structure of liver intermediate filaments

A dominating protein fraction (p45) having molecular weight of 45000 and pI 5.45 was found in the intermediate filaments pellet obtained from rat liver besides the present cytokeratins. Peptide mapping and radioimmunological assays with antibodies against this protein and muscle actin proved that the p45 protein belongs to the actin group. Immunoelectron microscopy revealed that this protein is located on the liver intermediate filaments. By melting of the cytokeratin complexes in urea it was established that p45 protein is complexed with the low molecular weight cytokeratin.     

Densely methylated DNA islands in mammalian chromosomal replication origins.

Densely methylated DNA sequence islands, designated DMIs, have been observed in two Chinese hamster cell chromosomal replication origins by using a PCR-based chemical method of detection. One of the origins, oriS14, is located within or adjacent to the coding sequence for ribosomal protein S14 on chromosome 2q, and the other, ori-beta, is approximately 17 kbp downstream of the dhfr (dihydrofolic acid reductase) locus on chromosome 2p. The DMI in oriS14 is 127 bp long, and the DMI in ori-beta is 516 bp long. Both DMIs are bilaterally methylated (i.e., all dCs are modified to 5-methyl dC) only in cells that are replicating their DNA. When cell growth and DNA replication are arrested, methylation of CpA, CpT, and CpC dinucleotides is lost and the sequence islands display only a subset of their originally methylated CpG dinucleotides. Several possible roles for DMI-mediated regulation of mammalian chromosomal origins are considered.     

Artifacts in sodium dodecyl sulfate-polyacrylamide gel electrophoresis due to 2-mercaptoethanol

Mercaptoethanol, when present in the sample buffer during sodium dodecyl sulfate-polyacrylamide gel electrophoresis, is responsible for the appearance of two nonprotein bands (electrophoretic mobilities corresponding to 68 and 54 kdalton) stainable with silver and with Coomassie blue. After iodination in vitro of DNA preparations isolated by alkaline phenol extraction using chloramine-T procedure, part of the radioactive label is found in these bands, provided the reaction is terminated by mercaptoethanol, whereas only a diffuse background is present in this area if the reaction is stopped by sodium metabisulfite. Similar results are obtained with highly purified total cytoplasmic RNA. The results indicate that the appearance of the 68- and 54-kdalton bands is in artifact. The relevance of these results to the proteins tightly bound to DNA is discussed.     

The promoter of filamentation (POF1) protein from <Emphasis Type="Italic">Saccharomyces cerevisiae</Emphasis> is an ATPase involved in the protein quality control process

Background

The gene YCL047C, which has been renamed promoter of filamentation gene (POF1), has recently been described as a cell component involved in yeast filamentous growth. The objective of this work is to understand the molecular and biological function of this gene.

Results

Here, we report that the protein encoded by the POF1 gene, Pof1p, is an ATPase that may be part of the Saccharomyces cerevisiae protein quality control pathway. According to the results, Δpof1 cells showed increased sensitivity to hydrogen peroxide, tert-butyl hydroperoxide, heat shock and protein unfolding agents, such as dithiothreitol and tunicamycin. Besides, the overexpression of POF1 suppressed the sensitivity of Δpct1, a strain that lacks a gene that encodes a phosphocholine cytidylyltransferase, to heat shock. In vitro analysis showed, however, that the purified Pof1p enzyme had no cytidylyltransferase activity but does have ATPase activity, with catalytic efficiency comparable to other ATPases involved in endoplasmic reticulum-associated degradation of proteins (ERAD). Supporting these findings, co-immunoprecipitation experiments showed a physical interaction between Pof1p and Ubc7p (an ubiquitin conjugating enzyme) in vivo.

Conclusions

Taken together, the results strongly suggest that the biological function of Pof1p is related to the regulation of protein degradation.

     

Testing the quick meal hypothesis: The effect of pulp on hoarding and seed predation of Hymenaea courbaril by red‐rumped agoutis (Dasyprocta leporina)

Abstract: Red‐rumped agoutis (Dasyprocta leporina) are important seed dispersers/predators of Neotropical large‐seeded plants. Several species of seeds cached by agoutis have an edible reward, in contrast to temperate rodent‐dispersed diaspores. The quick meal hypothesis states that the presence of a reward such as edible pulp will enhance the efficiency of rodents as seed disperses by satiating the animal and, consequently, reducing seed predation and enhancing hoarding. In this study, this hypothesis was tested using as the reference system the pulp and seeds of Hymenaea courbaril. Seeds with and without pulp were offered to agoutis and the behaviour of each individual was recorded. Since the probability of predation and hoarding were complementary, we used the probability of predation. The proportion of agoutis that preyed on at least one seed was similar for seeds with (42.8% of individuals) and without (40.0% of individuals) pulp. In agoutis that preyed upon at least one seed, the probability that they killed a seed did not differ between seeds with (0.17 ± 0.03) and without (0.20 ± 0.08) pulp. Hence, these results do not support the ‘quick meal hypothesis’.     

Interactions between an ectoparasitoid and a nucleopolyhedrovirus when simultaneously attacking Spodoptera exigua (Lepidoptera: Noctuidae)

Insect pathogenic viruses and parasitoids represent distinct biological entities that exploit a shared host resource and have similar effects in suppressing host populations. This study explores the interactions between the ectoparasitoid Euplectrus plathypenae (Hymenoptera: Eulophidae) and the Spodoptera exigua multiple nucleopolyhedrovirus (SeMNPV) in larvae of S. exigua (Lepidoptera: Noctuidae). Parasitoid progeny failed to complete development in hosts that had been infected prior to parasitism. However, infection of S. exigua fourth instars at 48 h post‐parasitism had no significant effects on the survival of parasitoid progeny. Larval and pupal development times of E. plathypenae that survived on virus‐infected S. exigua did not differ significantly from that of parasitoids on healthy hosts. Virus‐induced mortality and the production of occlusion bodies were very similar in parasitized and non‐parasitized S. exigua. The virus was genetically stable over three passages in parasitized and unparasitized hosts. These results suggest that applications of SeMNPV‐based insecticides are unlikely to disrupt pest control exerted by the parasitoid E. plathypenae in biological pest control programs as long as virus applications are timed not to coincide with parasitoid releases.     

Variants in the interleukin-1 alpha and beta genes,and the risk for periodontal disease in dogs

Elevated levels of interleukin-1 (IL-1) have been shown to amplify the inflammatory response against periodontopathogenic bacteria. In humans, polymorphisms in the IL1A and IL1B genes are the most well-studied genetic polymorphisms associated with periodontal disease (PD). In contrast to human, there is a lack of knowledge on the genetic basis of canine PD. A case–control study was conducted in which a molecular analysis of dog IL1A and IL1B genes was performed. Of the eight genetic variants identified, seven in IL1A gene and one in IL1B gene, IL1A/1_g.388A >C and IL1A/1_g.521T >A showed statistically significant differences between groups (adjusted OR (95% CI): 0.15 (0.03–0.76), P= 0.022; 5.76 (1.03–32.1), P= 0.046, respectively). It suggests that in the studied population the IL1A/1_g.388C allele is associated with a decreased PD risk, whereas the IL1A/1_g.521A allele can confer an increased risk. Additionally, the IL1A/2_g.515G >T variation resulted in a change of amino acid, i.e. glycine to valine. In silico analysis suggests that this change can alter protein structure and function, predicting it to be deleterious or damaging. This work suggests that IL1 genetic variants may be important in PD susceptibility in canines.     

Prevalence of tick-borne encephalitis virus antibodies in dogs from Denmark

Background  

Large regions of central and eastern Europe are recognized as areas where tick-borne encephalitis virus (TBEV) is endemic, including countries neighbouring Denmark. It is therefore timely and relevant to determine if TBEV infections occur in Denmark. This study investigates the presence of antibodies against TBEV in a cross-section of the Danish canine population to assess the level of exposure to TBEV and possibly identify TBEV microfoci in Denmark.