98 research outputs found

    Phosphorylation in the serine/threonine 2609–2647 cluster promotes but is not essential for DNA-dependent protein kinase-mediated nonhomologous end joining in human whole-cell extracts

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    Previous work suggested that phosphorylation of DNA-PKcs at several serine/threonine (S/T) residues at positions 2609–2647 promotes DNA-PK-dependent end joining. In an attempt to clarify the role of such phosphorylation, end joining was examined in extracts of DNA-PKcs-deficient M059J cells. Joining of ends requiring gap filling prior to ligation was completely dependent on complementation of these extracts with exogenous DNA-PKcs. DNA-PKcs with either S/T → A or S/T → D substitutions at all six sites in the 2609–2647 cluster also supported end joining, but with markedly lower efficiency than wild-type protein. The residual end joining was greater with the S/T → D-substituted than with the S/T → A-substituted protein. A specific inhibitor of the kinase activity of DNA-PK, KU57788, completely blocked end joining promoted by wild type as well as both mutant forms of DNA-PK, while inhibition of ATM kinase did not. The fidelity of end joining was not affected by the mutant DNA-PKcs alleles or the inhibitors. Overall, the results support a role for autophosphorylation of the 2609–2647 cluster in promoting end joining and controlling the accessibility of DNA ends, but suggest that DNA-PK-mediated phosphorylation at other sites, on either DNA-PKcs or other proteins, is at least as important as the 2609–2647 cluster in regulating end joining

    Coordinate 5′ and 3′ endonucleolytic trimming of terminally blocked blunt DNA double-strand break ends by Artemis nuclease and DNA-dependent protein kinase

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    Previous work showed that, in the presence of DNA-dependent protein kinase (DNA-PK), Artemis slowly trims 3′-phosphoglycolate-terminated blunt ends. To examine the trimming reaction in more detail, long internally labeled DNA substrates were treated with Artemis. In the absence of DNA-PK, Artemis catalyzed extensive 5′→3′ exonucleolytic resection of double-stranded DNA. This resection required a 5′-phosphate, but did not require ATP, and was accompanied by endonucleolytic cleavage of the resulting 3′ overhang. In the presence of DNA-PK, Artemis-mediated trimming was more limited, was ATP-dependent and did not require a 5′-phosphate. For a blunt end with either a 3′-phosphoglycolate or 3′-hydroxyl terminus, endonucleolytic trimming of 2–4 nucleotides from the 3′-terminal strand was accompanied by trimming of 6 nt from the 5′-terminal strand. The results suggest that autophosphorylated DNA-PK suppresses the exonuclease activity of Artemis toward blunt-ended DNA, and promotes slow and limited endonucleolytic trimming of the 5′-terminal strand, resulting in short 3′ overhangs that are trimmed endonucleolytically. Thus, Artemis and DNA-PK can convert terminally blocked DNA ends of diverse geometry and chemical structure to a form suitable for polymerase-mediated patching and ligation, with minimal loss of terminal sequence. Such processing could account for the very small deletions often found at DNA double-strand break repair sites

    Wine and other alcohol consumption and risk of ovarian cancer in the California Teachers Study cohort

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    OBJECTIVE: Whether alcohol consumption influences ovarian cancer risk is unclear. Therefore, we investigated the association between alcohol intake at various ages and risk of ovarian cancer. METHODS: Among 90,371 eligible members of the California Teachers Study cohort who completed a baseline alcohol assessment in 1995–1996, 253 women were diagnosed with epithelial ovarian cancer by the end of 2003. Multivariate Cox proportional hazards regression analysis was performed to estimate relative risks (RRs) and 95% confidence intervals (CIs). RESULTS: Consumption of total alcohol, beer, or liquor in the year prior to baseline, at ages 30–35 years, or at ages 18–22 years was not associated with risk of ovarian cancer. Consumption of at least one glass per day of wine, compared to no wine, in the year before baseline was associated with increased risk of developing ovarian cancer: RR = 1.57 (95% CI 1.11–2.22), P(trend) = 0.01. The association with wine intake at baseline was particularly strong among peri-/post-menopausal women who used estrogen-only hormone therapy and women of high socioeconomic status. CONCLUSIONS: Alcohol intake does not appear to affect ovarian cancer risk. Constituents of wine other than alcohol or, more likely, unmeasured determinants of wine drinking were associated with increased risk of ovarian cancer

    The transport mechanism of the mitochondrial ADP/ATP carrier

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    The mitochondrial ADP/ATP carrier imports ADP from the cytosol and exports ATP from the mitochondrial matrix, which are key transport steps for oxidative phosphorylation in eukaryotic organisms. The transport protein belongs to the mitochondrial carrier family, a large transporter family in the inner membrane of mitochondria. It is one of the best studied members of the family and serves as a paradigm for the molecular mechanism of mitochondrial carriers. Structurally, the carrier consists of three homologous domains, each composed of two transmembrane α-helices linked with a loop and short α-helix on the matrix side. The transporter cycles between a cytoplasmic and matrix state in which a central substrate binding site is alternately accessible to these compartments for binding of ADP or ATP. On both the cytoplasmic and matrix side of the carrier are networks consisting of three salt bridges each. In the cytoplasmic state, the matrix salt bridge network is formed and the cytoplasmic network is disrupted, opening the central substrate binding site to the intermembrane space and cytosol, whereas the converse occurs in the matrix state. In the transport cycle, tighter substrate binding in the intermediate states allows the interconversion of conformations by lowering the energy barrier for disruption and formation of these networks, opening and closing the carrier to either side of the membrane in an alternating way. Conversion between cytoplasmic and matrix states might require the simultaneous rotation of three domains around a central translocation pathway, constituting a unique mechanism among transport proteins. This article is part of a Special Issue entitled: Mitochondrial Channels edited by Pierre Sonveaux, Pierre Maechler and Jean-Claude Martinou

    Mothers construct fathers: Destabilized patriarchy in La Leche League

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    This paper examines changing masculine ideals from the point of view of women homemakers through a case study of La Leche League, a maternalist organization dedicated to breastfeeding and mother primacy. We suggest two reasons for studying the League: first, an emerging literature suggests that changing norms are seeping into many such seemingly conservative groups, and second, the League continues to be highly successful among white, middle-class, married women. The paper looks at two aspects of masculinity, examining changes in the League through fieldwork, interviews, and content analysis, and finds that new norms of increased father involvement and decreased rights over women's bodies have both influenced League philosophy. We conclude that while in some respects a measure of the decline of men's patriarchal privileges, the League's changes also may contribute to a “restabilization” of male dominance in a modified, partial form.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/43548/1/11133_2004_Article_BF00990071.pd
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