Long-term episomal maintenance of bovine papillomavirus type 1 plasmids is determined by attachment to host chromosomes, which Is mediated by the viral E2 protein and its binding sites

Papillomavirus genomes are stably maintained as extrachromosomal nuclear plasmids in dividing host cells. To address the mechanisms responsible for stable maintenance of virus, we examined nuclear compartmentalization of plasmids containing the full-length upstream regulatory region (URR) from the bovine papillomavirus type 1 (BPV1) genome. We found that these plasmids are tightly associated with the nuclear chromatin both in the stable cell lines that maintain episomal copies of the plasmids and in transiently transfected cells expressing the viral E1 and E2 proteins. Further analysis of viral factors revealed that the E2 protein in trans and its multiple binding sites in cis are both necessary and sufficient for the chromatin attachment of the plasmids. On the other hand, the BPV1 URR-dependent plasmid replication and chromatin attachment processes are clearly independent of each other. The ability of the plasmids to stably maintain episomes correlates clearly with their chromatin association function. These data suggest that viral E2 protein-mediated attachment of BPV1 genomes to the host cell chromatin could provide a mechanism for the coupling of viral genome multiplication and partitioning to the host cell cycle during viral latent infection.     

Biomass,composition and activity of organism assemblages along a salinity gradient in sea ice subjected to river discharge in the Baltic Sea

A study was undertaken to examine the activity and composition of the seasonal Baltic Sea land-fast sea-ice biota along a salinity gradient in March 2003 in a coastal location in the SW coast of Finland. Using a multi-variable data set, the less well-known algal and protozoan communities, and algal and bacterial production in relation to the physical and chemical environment were investigated. Also, the first coincident measurements of bacterial production and dissolved organic matter (DOM) in a sea-ice system are reported. Communities in sea ice were clearly autotrophy-dominated with algal biomass representing 79% of the total biomass. Protozoa and rotifers made up 18% of biomass in the ice and bacteria only 3%. Highest biomasses were found in mid-transect bottom ice. Water column assemblages were clearly more heterotrophic: 39% algae, 12% bacteria and 49% for rotifers and protozoa. Few significant correlations existed between DOM and bacterial variables, reflecting the complex origin of ice DOM. Dynamics of dissolved organic carbon, nitrogen and phosphorus (DOC, DON and DOP) were also uncoupled. A functional microbial loop is likely to be present in the studied ice. Existence of an under-ice freshwater plume affects the ecosystem functioning: Under-ice water communities are influenced directly by river-water mixing, whereas the ice system seems to be more independent—the interaction mainly taking place through the formation of active bottom communities.     

<Emphasis Type="Italic">Helicobacter pylori</Emphasis> genome variability in a framework of familial transmission

Background  

Helicobacter pylori infection is exceptionally prevalent and is considered to be acquired primarily early in life through person-to-person transmission within the family. H. pylori is a genetically diverse bacterial species, which may facilitate adaptation to new hosts and persistence for decades. The present study aimed to explore the genetic diversity of clonal isolates from a mother and her three children in order to shed light on H. pylori transmission and host adaptation.     

Different States of Acrylodan-Labeled 3′5′-Cyclic Adenosine Monophosphate Dependent Protein Kinase Catalytic Subunits in Denaturant Solutions

Fluorescence spectroscopy was used to differentiate between different states of acrylodan-labeled cAMP-dependent protein kinase catalytic subunits in urea, guanidine hydrochloride and 3-(N-morpholino)propanesulfonic acid solutions, by measuring changes in the emission spectrum of the protein-coupled dye, which is very sensitive to its microenvironment. Decomposition of the observed fluorescence spectra by a parameterized log-normal distribution function allowed the resolution of overlapping spectral bands and revealed the formation of three distinct protein states, denominated as native, denatured and unfolded structures. At low denaturant concentrations the formation of the denatured form from the native protein was observed, and this process was characterized by a blue-shift of the fluorescence spectrum of acrylodan, indicating that the dye was transferred into some water-deficit hydrophobic environment inside the protein molecule. Therefore, formation of a “dry molten globule” structure could be suggested in state. At high denaturant concentrations a red-shift of the emission spectrum of the protein-coupled probe was observed indicating significant extrusion of the dye molecule into water environment as a result of the unfolding of the protein structure.     

Histological and carbohydrate histochemical studies of the nasal mucosa of sheep in Saudi Arabia with special reference to its glandular tissue

The histology and carbohydrate histochemistry of the nasal mucosa with attention to glandular tissue had been studied in 7 heads of sheep. Tissues were taken from vestibular region, septum at level of the alar fold, rostral portion of nasal conchae, caudal portion of nasal conchae, middle portion of septum and ethmoidal conchae region. Stratified squamous nonkeratinized epithelium was observed covering the vestibular region. The propria-submucosa of the nasal vestibule was richly permeated with glands having affinity for PAS and non-alcianophilic. The post-vestibular portion of the nasal cavity was lined by transitional epithelium and caudal to it, stratified columnar nonciliated epithelium was noticed. The respiratory epithelium covered the caudal half of the nasal conchae and the major portion of the septum as well as the recesses of the ethmoidal conchae. The glands associated with the respiratory mucosa were thick, coiled and tubular, containing both nonalcianophilic PAS positive and alcianophilic PAS positive cells. The olfactory mucosa covered the ethmoidal conchae and showed predominant serous glands. The results were discussed with that given for other mammals and in regard to the respiratory functions of the nasal mucosa.     

Population dynamics of Agrimonia eupatoria and Geum rivale,two perennial grassland species

The population dynamics of two polycarpic perennials,Agrimonia eupatoria and Geum rivale, characteristic ofsemi-natural grasslands in Scandinavia, were examined in south-eastern Sweden.The perennial forbs were studied for several years in two populations each,located in habitats characteristic for the species in the study area.Demographic transition probabilities varied significantly between populationsand among years for the species. Transition matrix modelling yielded-values (population growth rates) that ranged from 0.89 to 1.14 forA. eupatoria and from 0.94 to 1.04 for G.rivale. The elasticity analysis showed that stasis in the adultstageclasses contributed most to . The life-table response experimentanalysis produced similar results as the elasticity analysis, where stasistogether with progression in the adult stage classes made a large contributionto the observed spatial variation in . Simulations of expected time toextinction were in the order of centuries for the study populations. Seedlingrecruitment was enhanced by seed addition and small scale disturbance inpopulations. For the intermediately abundant and more patchily distributedA. eupatoria, a regional survey of local populations wasconducted in the study area which revealed that most populations wererelativelysmall (< 100 individuals) and restricted to grassland fragments in roadverges. Furthermore, an attempt was made to estimate fruit dispersal from localpopulations.     

Effects of Antarctic sea ice biota on seeding as studied in aquarium experiments

Summary The potential seeding impact of sea ice microbial communities was studied during late austral winter early spring 1988 in the Weddell Sea, Antarctica. Experiments were performed in seawater aquariums with natural seawater and seawater enriched with crushed ice. Algal, protozoan and bacterial cell numbers were followed, as well as nutrients and DOC levels. The results showed a potential seeding effect of sea ice communities to the water column. However, the type of ice communities differed greatly from each other and the effect of such seeding will be patchy. In our experiments seeding of seawater by ice rich in algae, flagellates and/or particulate organic carbon lead to the development of communities dominated either by diatoms or bacteria.Data presented here were collected during the European Polarstern Study (EPOS) sponsored by the European Science Foundation     

Allosteric Effect of Adenosine Triphosphate on Peptide Recognition by 3′5′-Cyclic Adenosine Monophosphate Dependent Protein Kinase Catalytic Subunits

The allosteric influence of adenosine triphosphate (ATP) on the binding effectiveness of a series of peptide inhibitors with the catalytic subunit of 3′5′-cyclic adenosine monophosphate dependent protein kinase was investigated, and the dependence of this effect on peptide structure was analyzed. The allosteric effect was calculated as ratio of peptide binding effectiveness with the enzyme-ATP complex and with the free enzyme, quantified by the competitive inhibition of the enzyme in the presence of ATP excess, and by the enzyme-peptide complex denaturation assay, respectively It was found that the principle “better binding—stronger allostery” holds for interactions of the studied peptides with the enzyme, indicating that allostery and peptide binding with the free enzyme are governed by the same specificity pattern. This means that the allosteric regulation does not include new ligand–protein interactions, but changes the intensity (strength) of the interatomic forces that govern the complex formation in the case of each individual ligand. We propose that the allosteric regulation can be explained by the alteration of the intrinsic dynamics of the protein by ligand binding, and that this phenomenon, in turn, modulates the ligand off-rate from its binding site as well as the binding affinity. The positive allostery could therefore be induced by a reduction in the enzyme’s overall intrinsic dynamics.