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ABSTRACT: DNA transposons are mobile genetic elements that have shaped the genomes of eukaryotes for millions of years, yet their origins remain obscure. We discovered a virophage that, on the basis of genetic homology, likely represents an evolutionary link between double-stranded DNA viruses and Maverick/Polinton eukaryotic DNA transposons. The Mavirus virophage parasitizes the giant Cafeteria roenbergensis virus and encodes 20 predicted proteins, including a retroviral integrase and a protein-primed DNA polymerase B. On the basis of our data, we conclude that Maverick/Polinton transposons may have originated from ancient relatives of Mavirus, and thereby influenced the evolution of eukaryotic genomes, although we cannot rule out alternative evolutionary scenarios.
Science 03/2011; 332(6026):231-4. · 31.20 Impact Factor
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ABSTRACT: As major consumers of heterotrophic bacteria and phytoplankton, microzooplankton are a critical link in aquatic foodwebs. Here, we show that a major marine microflagellate grazer is infected by a giant virus, Cafeteria roenbergensis virus (CroV), which has the largest genome of any described marine virus (≈730 kb of double-stranded DNA). The central 618-kb coding part of this AT-rich genome contains 544 predicted protein-coding genes; putative early and late promoter motifs have been detected and assigned to 191 and 72 of them, respectively, and at least 274 genes were expressed during infection. The diverse coding potential of CroV includes predicted translation factors, DNA repair enzymes such as DNA mismatch repair protein MutS and two photolyases, multiple ubiquitin pathway components, four intein elements, and 22 tRNAs. Many genes including isoleucyl-tRNA synthetase, eIF-2γ, and an Elp3-like histone acetyltransferase are usually not found in viruses. We also discovered a 38-kb genomic region of putative bacterial origin, which encodes several predicted carbohydrate metabolizing enzymes, including an entire pathway for the biosynthesis of 3-deoxy-d-manno-octulosonate, a key component of the outer membrane in Gram-negative bacteria. Phylogenetic analysis indicates that CroV is a nucleocytoplasmic large DNA virus, with Acanthamoeba polyphaga mimivirus as its closest relative, although less than one-third of the genes of CroV have homologs in Mimivirus. CroV is a highly complex marine virus and the only virus studied in genetic detail that infects one of the major groups of predators in the oceans.
Proceedings of the National Academy of Sciences 10/2010; 107(45):19508-13. · 9.68 Impact Factor
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ABSTRACT: Mps1 kinase plays an evolutionary conserved role in the mitotic spindle checkpoint. This system precludes anaphase onset until all chromosomes have successfully attached to spindle microtubules via their kinetochores. Mps1 overexpression in budding yeast is sufficient to trigger a mitotic arrest, which is dependent on the other mitotic checkpoint components, Bub1, Bub3, Mad1, Mad2, and Mad3. Therefore, Mps1 might act at the top of the mitotic checkpoint cascade. Moreover, in contrast to the other mitotic checkpoint components, Mps1 is essential for spindle pole body duplication in budding yeast. Centrosome duplication in mammalian cells might also be controlled by Mps1 , but the fission yeast homolog is not required for spindle pole body duplication. Our phenotypic characterizations of Mps1 mutant embryos in Drosophila do not reveal an involvement in centrosome duplication, while the mitotic spindle checkpoint is defective in these mutants. In addition, our analyses reveal novel functions. We demonstrate that Mps1 is also required for the arrest of cell cycle progression in response to hypoxia. Finally, we show that Mps1 and the mitotic spindle checkpoint are responsible for the developmental cell cycle arrest of the three haploid products of female meiosis that are not used as the female pronucleus.
Current Biology 12/2004; 14(22):2019-24. · 9.65 Impact Factor
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ABSTRACT: The existence of cellular genes in viruses such as the nucleocytoplasmic large DNA viruses (NCLDV) has led to not only the redefinition of the virus but also the mystery of the origin of these genes. Cafeteria roenbergensis virus (CroV) is a giant marine virus in the NCLDV clade. Information obtained from structural proteomics studies of CroV can be compared with known cellular counterparts, elucidating the evolutionary relationship between virus and cell in a three-dimensional structural aspect. CroV's major capsid protein gene (MCP) and five CroV genes, (CDS 84, 115, 143, 149,152) including a photolyase and an oxidoreductase, have been chosen to be cloned, expressed, and crystallized to determine their atomic structures. Cloning will be accomplished using Invitrogen's Gateway System, which confers the advantage of accessibility to different expression systems. Proteins will be purified to high homogeneity via affinity chromatography for screening of crystallization conditions. Atomic structures will be determined through x-ray crystallography. CroV genes 84, 115, 143, 149, and 152 are in the cloning phase and the MCP gene is in protein expression trials. Comparisons to homologous proteins, functional analyses, and mutagenesis studies will follow to extend the proteomics study of CroV.
COURI Symposium Abstracts, Spring 2011.
