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  • 1
    Publication Date: 2014-12-10
    Description: The widespread reorganization of cellular architecture in mitosis is achieved through extensive protein phosphorylation, driven by the coordinated activation of a mitotic kinase network and repression of counteracting phosphatases. Phosphatase activity must subsequently be restored to promote mitotic exit. Although Cdc14 phosphatase drives this reversal in budding yeast, protein phosphatase 1 (PP1) and protein phosphatase 2A (PP2A) activities have each been independently linked to mitotic exit control in other eukaryotes. Here we describe a mitotic phosphatase relay in which PP1 reactivation is required for the reactivation of both PP2A-B55 and PP2A-B56 to coordinate mitotic progression and exit in fission yeast. The staged recruitment of PP1 (the Dis2 isoform) to the regulatory subunits of the PP2A-B55 and PP2A-B56 (B55 also known as Pab1; B56 also known as Par1) holoenzymes sequentially activates each phosphatase. The pathway is blocked in early mitosis because the Cdk1-cyclin B kinase (Cdk1 also known as Cdc2) inhibits PP1 activity, but declining cyclin B levels later in mitosis permit PP1 to auto-reactivate. PP1 first reactivates PP2A-B55; this enables PP2A-B55 in turn to promote the reactivation of PP2A-B56 by dephosphorylating a PP1-docking site in PP2A-B56, thereby promoting the recruitment of PP1. PP1 recruitment to human, mitotic PP2A-B56 holoenzymes and the sequences of these conserved PP1-docking motifs suggest that PP1 regulates PP2A-B55 and PP2A-B56 activities in a variety of signalling contexts throughout eukaryotes.〈br /〉〈br /〉〈a href="https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4338534/" target="_blank"〉〈img src="https://static.pubmed.gov/portal/portal3rc.fcgi/4089621/img/3977009" border="0"〉〈/a〉   〈a href="https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4338534/" target="_blank"〉This paper as free author manuscript - peer-reviewed and accepted for publication〈/a〉〈br /〉〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Grallert, Agnes -- Boke, Elvan -- Hagting, Anja -- Hodgson, Ben -- Connolly, Yvonne -- Griffiths, John R -- Smith, Duncan L -- Pines, Jonathon -- Hagan, Iain M -- 092096/Wellcome Trust/United Kingdom -- A13678/Cancer Research UK/United Kingdom -- A16406/Cancer Research UK/United Kingdom -- C147/A16406/Cancer Research UK/United Kingdom -- C29/A13678/Cancer Research UK/United Kingdom -- England -- Nature. 2015 Jan 1;517(7532):94-8. doi: 10.1038/nature14019. Epub 2014 Dec 10.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Cell Division Group, CRUK Manchester Institute, University of Manchester, Wilmslow Road, Manchester M20 4BX, UK. ; The Gurdon Institute, Tennis Court Road, University of Cambridge, Cambridge, CB2 1QN, UK. ; Biological Mass Spectrometry, CRUK Manchester Institute, University of Manchester, Wilmslow Road, Manchester M20 4BX, UK.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/25487150" target="_blank"〉PubMed〈/a〉
    Keywords: Amino Acid Motifs ; Amino Acid Sequence ; Binding Sites ; CDC2 Protein Kinase/metabolism ; Chromosome Segregation ; Conserved Sequence ; Cyclin B/metabolism ; Enzyme Activation ; HeLa Cells ; Holoenzymes/metabolism ; Humans ; Isoenzymes/metabolism ; *Mitosis ; Molecular Sequence Data ; Phosphorylation ; Protein Phosphatase 1/*metabolism ; Protein Phosphatase 2/chemistry/*metabolism ; Protein Subunits/chemistry/metabolism ; Schizosaccharomyces/*cytology/*enzymology ; Schizosaccharomyces pombe Proteins/chemistry/metabolism ; Signal Transduction
    Print ISSN: 0028-0836
    Electronic ISSN: 1476-4687
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
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  • 2
    Publication Date: 2013-04-14
    Description: Archaeal family-D DNA polymerase is inhibited by the presence of uracil in DNA template strands. When the enzyme encounters uracil, following three parameters change: DNA binding increases roughly 2-fold, the rate of polymerization slows by a factor of ~5 and 3'–5' proof-reading exonuclease activity is stimulated by a factor of ~2. Together these changes result in a significant decrease in polymerization activity and a reduction in net DNA synthesis. Pol D appears to interact with template strand uracil irrespective of its distance ahead of the replication fork. Polymerization does not stop at a defined location relative to uracil, rather a general decrease in DNA synthesis is observed. ‘Trans’ inhibition, the slowing of Pol D by uracil on a DNA strand not being replicated is also observed. It is proposed that Pol D is able to interact with uracil by looping out the single-stranded template, allowing simultaneous contact of both the base and the primer-template junction to give a polymerase-DNA complex with diminished extension ability.
    Print ISSN: 0305-1048
    Electronic ISSN: 1362-4962
    Topics: Biology
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  • 3
    Publication Date: 2014-10-14
    Description: Porosity waves are a mechanism by which fluid generated by devolatilization and melting, or trapped during sedimentation, may be expelled from ductile rocks. The waves correspond to a steady-state solution to the coupled hydraulic and rheologic equations that govern flow of the fluid through the matrix and matrix deformation. This work presents an intuitive analytical formulation of this solution in one dimension that is general with respect to the constitutive relations used to define the viscous matrix rheology and permeability. This generality allows for the effects of nonlinear viscous matrix rheology and disaggregation. The solution combines the porosity dependence of the rheology and permeability in a single hydromechanical potential as a function of material properties and wave velocity. With the ansatz that there is a local balance between fluid production and transport, the solution permits prediction of the dynamic variations in permeability and pressure necessary to accommodate fluid production. The solution is used to construct a phase diagram that defines the conditions for smooth pervasive flow, wave-propagated flow, and matrix fluidization (disaggregation). The viscous porosity wave mechanism requires negative effective pressure to open the porosity in the leading half of a wave. In nature, negative effective pressure may induce hydrofracture, resulting in a viscoplastic compaction rheology. The tubelike porosity waves that form in such a rheology channelize fluid expulsion and are predicted by geometric argumentation from the one-dimensional viscous solitary wave solution. Porosity waves are the steady-state response to flow perturbations such as fluid production in ductile rocks. This study develops an analytical solution for these waves that is general with respect to the constitutive relations that define the viscous matrix rheology and permeability. The analytical solution permits anticipation of the scales of lower crustal fluid pressure and permeability variations caused by flow perturbations.
    Print ISSN: 1468-8115
    Electronic ISSN: 1468-8123
    Topics: Geosciences
    Published by Wiley
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