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Rauscher spleen focus-forming virus contains functional gag and pol genes and a partially deleted env gene which is structurally related to the env genes of dual tropic murine leukemia viruses.
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In prokaryotic and eukaryotic organisms, biochemical and physiological processes are sensitive to changes in H(+) activity. For these processes to function optimally, a variety of proteins have evolved that transport H(+)/base equivalents across cell and organelle membranes, thereby maintaining the pH of various intracellular and extracellular compartments within specific limits. The SLC4 family of base (HCO(3)(-), CO(3)(2(-))) transport proteins plays an essential role in mediating Na(+)- and/or Cl(-)-dependent base transport in various tissues and cell types in mammals. In addition to pH regulation, specific members of this family also contribute to vectorial transepithelial base transport in several organ systems including the kidney, pancreas, and eye. The importance of these transporters in mammalian cell biology is highlighted by the phenotypic abnormalities resulting from spontaneous SLC4 mutations in humans and targeted deletions in murine knockout models. This review focuses on recent advances in our understanding of the molecular organization and functional properties of SLC4 transporters and their role in disease.
Vascular network remodeling, angiogenesis, and arteriogenesis play an important role in the pathophysiology of ischemic cardiovascular diseases and cancer. Based on recent studies of vascular network development in the embryo, several novel aspects to angiogenesis have been identified as crucial to generate a functional vascular network. These aspects include specification of arterial and venous identity in vessels and network patterning. In early embryogenesis, vessel identity and positioning are genetically hardwired and involve neural guidance genes expressed in the vascular system. We demonstrated that, during later stages of embryogenesis, blood flow plays a crucial role in regulating vessel identity and network remodeling. The flow-evoked remodeling process is dynamic and involves a high degree of vessel plasticity. The open question in the field is how genetically predetermined processes in vessel identity and patterning balance with the contribution of blood flow in shaping a functional vascular architecture. Although blood flow is essential, it remains unclear to what extent flow is able to act on the developing cardiovascular system. There is significant evidence that mechanical forces created by flowing blood are biologically active within the embryo and that the level of mechanical forces and the type of flow patterns present in the embryo are able to affect gene expression. Here, we highlight the pivotal role for blood flow and physical forces in shaping the cardiovascular system.
The effects of temperature and type of host on the evolution of variants in replicating populations of tobacco mosaic virus (TMV) originating from an in vitro RNA transcript of a cDNA clone were studied. The phenotypic markers measured were temperature-sensitive (ts) replication and induction of necrotic local lesions (nl) on Nicotiana sylvestris. The proportions of ts variants were about the same under all conditions tested, but changes in temperature or host had strong effects on proportions of nl variants. During replication at elevated temperatures in tobacco or tomato, percentages of nl variants were reduced rapidly to about one tenth their initial values. In contrast, when virus replicated at 25 degrees in tobacco, little change in the average proportion of nl variants was observed, and in tomato, only a slight average reduction occurred. Virus replicating at 25 degrees in Solanum nigrum or Petunia hybrida suffered effects similar to those observed in tobacco or tomato, respectively. However, at 25 degrees in Physalis floridana, there was strong selection against nl variants, which eventually reduced them to essentially undetectable levels. In all hosts tested at 25 degrees, surprisingly large, apparently random changes in the proportion of nl variants occurred in individual plants. These experiments showed that virus populations can evolve rapidly on a time scale of days, and that an element of randomness is an important component in the initiation of change.
BACKGROUND: Vps25p is the product of yeast gene VPS25 and is found in an endosomal sorting complex required for transport (ESCRT)-II, along with Vps22p and Vps36p. This complex is essential for sorting of ubiquitinated biosynthetic and endosomal cargoes into endosomes. RESULTS: We found that VPS25 is a highly conserved and widely expressed eukaryotic gene, with single orthologs in chromalveolate, excavate, amoebozoan, plant, fungal and metazoan species. Two paralogs were found in Trichomonas vaginalis. An ortholog was strikingly absent from the Encephalitozoon cuniculi genome. Intron positions were analyzed in VPS25 from 36 species. We found evidence for five ancestral VPS25 introns, intron loss, and single instances of intron gain (a Paramecium species) and intron slippage (Theileria species). Processed pseudogenes were identified in four mammalian genomes, with a notable absence in the mouse genome. Two retropseudogenes were found in the chimpanzee genome, one more recently inserted, and one evolving from a common primate ancestor. The amino acid sequences of 119 Vps25 orthologs are aligned, compared with the known secondary structure of yeast Vps25p, and used to carry out phylogenetic analysis. Residues in two amino-terminal PPXY motifs (motif I and II), involved in dimerization of Vps25p and interaction with Vps22p and Vps36p, were closely, but not absolutely conserved. Specifically, motif I was absent in Vps25 homologs of chromalveolates, euglenozoa, and diplomonads. A highly conserved carboxy-terminal lysine was identified, which suggests Vps25 is ubiquitinated. Arginine-83 of yeast Vps25p involved in Vps22p interaction was highly, but not absolutely, conserved. Human tissue expression analysis showed universal expression. CONCLUSION: We have identified 119 orthologs of yeast Vps25p. Expression of mammalian VPS25 in a wide range of tissues, and the presence in a broad range of eukaryotic species, indicates a basic role in eukaryotic cell function. Intron splice site positions were highly conserved across all major eukaryotic species, suggesting an ancestral origin. Amino acid sequence analysis showed the consensus for the amino-terminal proline-rich motifs is P- [WP]-X-[YF] for motif I (when present) and P-P-[FYL]-[FY] for motif II, and that Vps25 may be ubiquitinated.
Analysis of receptor tyrosine kinases expressed during mouse embryonic stem cell differentiation resulted in the cloning of a receptor designated developmental tyrosine kinase (DTK). The 850 amino acid mature receptor protein comprises an extracellular domain with two immunoglobulin-like motifs and two fibronectin type III modules, a 25 amino acid transmembrane domain and a cytoplasmic region with a catalytic kinase domain. In embryonic stem cells growing in the presence of leukemia inhibitory factor DTK is abundantly expressed and this level of expression is maintained in differentiating embryonic stem cells and cystic embryoid bodies. In mid-gestational embryos (E14.5), DTK RNA is expressed in many tissues including brain, eye, thymus, lung, heart, gut, liver, testis and limbs. In contrast, expression of DTK in adult mice becomes restricted to brain, portions of the gastrointestinal tract, bladder, testis and ovary. There is enrichment of transcripts encoding DTK in purified fetal liver hematopoietic stem cells, when compared with unfractionated fetal liver. The DTK gene maps to mouse chromosome 2, band F.
The cytokine termed hepatocyte growth factor or scatter factor (HGF/SF) has been implicated in embryonic development and liver regeneration. Mouse HGF/SF cDNA clones were obtained by screening a mouse liver cDNA library with synthetic oligonucleotides, as well as by using the method of reverse transcription-polymerase chain reaction (RT-PCR) with mRNA isolated from adult mouse brain. Sequence analysis of mouse HGF/SF cDNA clones spanning the entire coding region revealed an overall amino acid identity of 90% and 98% with human and rat HGF, respectively. Using mouse HGF antisense RNA as a probe, we observed the expression of HGF/SF mRNA in the liver, kidney, whole brain and cerebellum of adult mice as well as in day 9 and day 10 mouse embryos. The mouse HGF/SF cDNA was utilized for mapping Hgf to the centromeric region of mouse Chromosome 5 in apparent close proximity to the reeler mutation by the analysis of two multilocus crosses. The relationship of Hgf to the reeler mutation is discussed. The availability of mouse HGF/SF cDNA clones should facilitate further analysis of HGF/SF function during development.
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Genomic libraries were obtained from species belonging to the "virilis" group of Drosophila. Several copies of Penelope elements were isolated from these libraries by using a D. virilis Penelope clone as a probe. The elements were sequenced, and their structure was determined. The geographical distribution of this family of mobile elements in closely related species of the group was studied in detail. Cytological localization of the elements was also carried out. The high variability observed between different copies of Penelope is probably due to recombination between individual copies. The role of these elements in the evolution of closely related species is discussed.
Results of the first in Russia survey of the gene pool of the breeding nucleus of the Russian population of thoroughbred horses by means of PCR analysis of the E (Extension) locus MC1R gene mutations are presented. The data on the structure of breeding populations from the leading stud farms Voskhod and Oros with regard to color phenotypes as well as genotype and allele frequencies are presented. The population structure parameters are discussed with respect to possible specific features of microevolution processes.
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OBJECTIVE: To clone the gene of plasmid-mediated AmpC beta-lactamase from the plasmid of multiple-drug resistance Klebsiella pneumoniae producing plasmid-mediated AmpC beta-lactamase and demonstrate its mechanism of transmission. METHODS: Plasmids of the transconjugant were extracted and digested with restriction endonuclease HindIII. Taq DNA polymerase was applied to fill the recessed 3' termini, and a single deoxyadenosine was added to the 3' termimi of fragments. Then these fragments were ligated with pGEM-T Easy vector. E. coli DH5alpha containing recombinant plasmid was selected on MacConkey agar plates containing ampicillin and cefoxitin. Insert fragments were sequenced by primer walking. MIC determinations and isoelectric focusing electrophoresis (IFE) were utilized to analyze recombinant. RESULTS: The recombinant plasmid pT948 containing a 5.2-kb insert was obtained. The inserted fragment contained a bla(DHA-1) and a regulatory gene ampR. The insertion sequence (IS26), qacEDelta1 and sulI genes of the I type integron were obtained near the bla(DHA-1) gene. Recombinant expressed a beta-lactamase with pI of 7.7. MIC determinations showed that recombinant was resistant to cefoxitin and the resistance to ceftazidime could be induced by the cefoxitin. CONCLUSION: The plasmid-mediated ampC gene cloned was identified as bla(DHA-1). IS26 observed on the flanks of the bla(DHA-1) maybe relate to the translocation of bla(DHA-1) gene region from the chromosome to plasmid.
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