1,720,980 research outputs found
Purification and functional inactivation of the fission yeast MCMMCM–BP complex
No full textAbstractThe MCM (mini-chromosome maintenance) complex is the core of the eukaryotic replicative helicase and comprises six proteins, Mcm2–Mcm7. In humans, a variant form of the complex has Mcm2 replaced by the MCM–BP protein. Recent results suggest that a similar complex exists in fission yeast with an essential role in DNA replication and cell cycle progression. Here, we describe the purification and subunit composition of the fission yeast MCMMcb1 complex. Using newly generated temperature-sensitive alleles, we show that loss of MCMMcb1 function leads to accumulation of DNA damage, checkpoint activation and cell cycle arrest, and provide evidence for a role for MCMMcb1 in meiosis.Structured summary of protein interactionsMcb1 physically interacts with Mcm4 by pull down (View interaction)Mcb1 physically interacts with Mcm5 by pull down (View interaction)Mcb1 physically interacts with Mcm6 by pull down (View interaction)Mcm4 and Mcb1 physically interact by bimolecular fluorescence complementation (View interaction)Mcb1 physically interacts with Mcm3, Mcm4, Mcm5, Mcm6 and Mcm7 by tandem affinity purification (View interaction)Mcb1 physically interacts with Mcm7 by pull down (View interaction
Genetics of lagging strand DNA synthesis and maturation in fission yeast:suppression analysis links the Dna2-Cdc24 complex to DNA polymerase delta
No full textThe Cdc24 protein is essential for the completion of chromosomal DNA replication in fission yeast. Although its precise role in this process is unclear, Cdc24 forms a complex with Dna2, a conserved endonuclease-helicase implicated in the removal of the RNA-DNA primer during Okazaki fragment processing. To gain further insights into Cdc24-Dna2 function, we screened for chromosomal suppressors of the temperature-sensitive cdc24-M38 allele and mapped the suppressing mutations into six complementation groups. Two of these mutations defined genes encoding the Pol3 and Cdc27 subunits of DNA polymerase delta. Sequence analysis revealed that all the suppressing mutations in Cdc27 resulted in truncation of the protein and loss of sequences that included the conserved C-terminal PCNA binding motif, previously shown to play an important role in maximizing enzyme processivity in vitro. Deletion of this motif is shown to be sufficient for suppression of both cdc24-M38 and dna2-C2, a temperature-sensitive allele of dna2(+), suggesting that disruption of the interaction between Cdc27 and PCNA renders the activity of the Cdc24-Dna2 complex dispensable.</p
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
The fission yeast <em>pfh1</em> gene encodes an essential 5' to 3' DNA helicase required for the completion of S-phase
No full textThe Cdc24 protein plays an essential role in chromosomal DNA replication in the fission yeast Schizosaccharomyces pombe, most likely via its direct interaction with Dna2, a conserved endonuclease-helicase protein required for Okazaki fragment processing. To gain insights into Cdc24 function, we isolated cold-sensitive chromosomal suppressors of the temperature-sensitive cdc24-M38 allele. One of the complementation groups of such suppressors defined a novel gene, pfh1(+), encoding an 805 amino acid nuclear protein highly homologous to the Saccharomyces cerevisiae Pif1p and Rrm3p DNA helicase family proteins. The purified Pfh1 protein displayed single-stranded DNA-dependent ATPase activity as well as 5' to 3' DNA helicase activity in vitro. Reverse genetic analysis in S.pombe showed that helicase activity was essential for the function of the Pfh1 protein in vivo. Schizosaccharomyces pombe cells carrying the cold-sensitive pfh1-R20 allele underwent cell cycle arrest in late S/G2-phase of the cell cycle when shifted to the restrictive temperature. This arrest was dependent upon the presence of a functional late S/G2 DNA damage checkpoint, suggesting that Pfh1 is required for the comple tion of DNA replication. Furthermore, at their permissive temperature pfh1-R20 cells were highly sensitive to the DNA-alkylating agent methyl methanesulphonate, implying a further role for Pfh1 in the repair of DNA damage.</p
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Full text linkWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
Genetic analyses of Schizosaccharomyces pombe dna2(+) reveal that Dna2 plays an essential role in Okazaki fragment metabolism
No full textIn this report, we investigated the phenotypes caused by temperature-sensitive (ts) mutant alleles of dna(2+) of Schizosaccharomyces pombe, a homologue of DNA2 of budding yeast, in an attempt to further define its function in vivo with respect to lagging-strand synthesis during the S-phase of the cell cycle. At the restrictive temperature, dna2 (ts) cells arrested at late S-phase but were unaffected in bulk DNA synthesis. Moreover, they exhibited aberrant mitosis when combined xith checkpoint mutations, in keeping with a role for Dna2 in Okazaki fragment maturation. Similarly, spores in which dna2(+) was disrupted duplicated their DNA content during germination and also arrested at late S-phase. Inactivation of dna(2+) led to chromosome fragmentation strikingly similar to that seen when cdc17(+), the DNA ligase I gene, is inactivated The temperature-dependent lethality of dna2 (ts) mutants was suppressed by overexpression of genes encoding subunits of polymerase delta (cdc1(+) and cdc27(+)), DNA ligase I (cdc17(+)), and Fen-l (rad2(+)). Each of these gene products plays a role in the elongation or maturation of Okazaki fragments. Moreover, they all interacted with S. pombe Dna2 in a yeast two-hybrid assay, albeit to different extents. On the basis of these results, ive conclude that dna2(+) plays a direct role in the Okazaki fragment elongation and maturation. We propose that dna2(+) acts as a central protein to form a complex with other proteins required to coordinate the multienzyme process for Okazaki fragment elongation and maturation
Dispelling the Myths Behind First-author Citation Counts
Full text linkWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
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