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Search Results: 1 - 10 of 166002 matches for " Paul B Talbert "
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Centromeres Convert but Don't Cross
Paul B. Talbert,Steven Henikoff
PLOS Biology , 2012, DOI: 10.1371/journal.pbio.1000326
Abstract:
Centromeres Convert but Don't Cross
Paul B. Talbert,Steven Henikoff
PLOS Biology , 2010, DOI: 10.1371/journal.pbio.1000326
Abstract:
Adaptive evolution of centromere proteins in plants and animals
Talbert Paul B,Bryson Terri D,Henikoff Steven
Journal of Biology , 2004, DOI: 10.1186/jbiol11
Abstract: Background Centromeres represent the last frontiers of plant and animal genomics. Although they perform a conserved function in chromosome segregation, centromeres are typically composed of repetitive satellite sequences that are rapidly evolving. The nucleosomes of centromeres are characterized by a special H3-like histone (CenH3), which evolves rapidly and adaptively in Drosophila and Arabidopsis. Most plant, animal and fungal centromeres also bind a large protein, centromere protein C (CENP-C), that is characterized by a single 24 amino-acid motif (CENPC motif). Results Whereas we find no evidence that mammalian CenH3 (CENP-A) has been evolving adaptively, mammalian CENP-C proteins contain adaptively evolving regions that overlap with regions of DNA-binding activity. In plants we find that CENP-C proteins have complex duplicated regions, with conserved amino and carboxyl termini that are dissimilar in sequence to their counterparts in animals and fungi. Comparisons of Cenpc genes from Arabidopsis species and from grasses revealed multiple regions that are under positive selection, including duplicated exons in some grasses. In contrast to plants and animals, yeast CENP-C (Mif2p) is under negative selection. Conclusions CENP-Cs in all plant and animal lineages examined have regions that are rapidly and adaptively evolving. To explain these remarkable evolutionary features for a single-copy gene that is needed at every mitosis, we propose that CENP-Cs, like some CenH3s, suppress meiotic drive of centromeres during female meiosis. This process can account for the rapid evolution and the complexity of centromeric DNA in plants and animals as compared to fungi.
Intergenic Locations of Rice Centromeric Chromatin
Huihuang Yan,Paul B. Talbert,Hye-Ran Lee,Jamie Jett,Steven Henikoff,Feng Chen,Jiming Jiang
PLOS Biology , 2012, DOI: 10.1371/journal.pbio.0060286
Abstract: Centromeres are sites for assembly of the chromosomal structures that mediate faithful segregation at mitosis and meiosis. Plant and animal centromeres are typically located in megabase-sized arrays of tandem satellite repeats, making their precise mapping difficult. However, some rice centromeres are largely embedded in nonsatellite DNA, providing an excellent model to study centromere structure and evolution. We used chromatin immunoprecipitation and 454 sequencing to define the boundaries of nine of the 12 centromeres of rice. Centromere regions from chromosomes 8 and 9 were found to share synteny, most likely reflecting an ancient genome duplication. For four centromeres, we mapped discrete subdomains of binding by the centromeric histone variant CENH3. These subdomains were depleted in both intact and nonfunctional genes relative to interspersed subdomains lacking CENH3. The intergenic location of rice centromeric chromatin resembles the situation for human neocentromeres and supports a model of the evolution of centromeres from gene-poor regions.
Intergenic Locations of Rice Centromeric Chromatin
Huihuang Yan,Paul B Talbert,Hye-Ran Lee,Jamie Jett,Steven Henikoff,Feng Chen ,Jiming Jiang
PLOS Biology , 2008, DOI: 10.1371/journal.pbio.0060286
Abstract: Centromeres are sites for assembly of the chromosomal structures that mediate faithful segregation at mitosis and meiosis. Plant and animal centromeres are typically located in megabase-sized arrays of tandem satellite repeats, making their precise mapping difficult. However, some rice centromeres are largely embedded in nonsatellite DNA, providing an excellent model to study centromere structure and evolution. We used chromatin immunoprecipitation and 454 sequencing to define the boundaries of nine of the 12 centromeres of rice. Centromere regions from chromosomes 8 and 9 were found to share synteny, most likely reflecting an ancient genome duplication. For four centromeres, we mapped discrete subdomains of binding by the centromeric histone variant CENH3. These subdomains were depleted in both intact and nonfunctional genes relative to interspersed subdomains lacking CENH3. The intergenic location of rice centromeric chromatin resembles the situation for human neocentromeres and supports a model of the evolution of centromeres from gene-poor regions.
A unified phylogeny-based nomenclature for histone variants
Paul B Talbert, Kami Ahmad, Geneviève Almouzni, Juan Ausió, Frederic Berger, Prem L Bhalla, William M Bonner, W Cande, Brian P Chadwick, Simon W L Chan, George A M Cross, Liwang Cui, Stefan I Dimitrov, Detlef Doenecke, José M Eirin-López, Martin A Gorovsky, Sandra B Hake, Barbara A Hamkalo, Sarah Holec, Steven E Jacobsen, Kinga Kamieniarz, Saadi Khochbin, Andreas G Ladurner, David Landsman, John A Latham, Benjamin Loppin, Harmit S Malik, William F Marzluff, John R Pehrson, Jan Postberg
Epigenetics & Chromatin , 2012, DOI: 10.1186/1756-8935-5-7
Abstract: Histones, the basic proteins that wrap DNA into nucleosomes in eukaryotes, are commonly encoded by multigene families. Histones fall into five protein families, the core histones H2A, H2B, H3 and H4, and the linker histone family H1. A nucleosome core particle is made by assembling two proteins from each of the core histone families together with DNA. Linker DNA between core particles may be bound by a member of the H1 family. The individual paralogous (non-allelic) genes of a histone family may encode identical proteins, or they may encode related but distinct protein isoforms, commonly referred to as “histone variants”. Though histone variants have been known almost from the beginning of histone research, we are still discovering the diversity of their roles and functions. Histone variants play critical roles in such diverse processes as transcription, chromosome segregation, DNA repair and recombination, chromatin remodeling, ADP-ribosylation, germline-specific DNA packaging and activation, and even extra-nuclear acrosomal function. Some variants of H2A and H3 have well-studied, specialized functions. Variants of H1 and H2B are common, but much less is known of their functional specialization. H4 variants are few.The diversity of core histones has led to confusion in naming since their discovery. The current names - H2A, H2B, H3 and H4 - for the ‘canonical’ histones were agreed upon at the Ciba Foundation Symposium in 1975 to simplify and standardize competing names for these proteins based on different methods of extraction [1]. At that time, the first core histone variants of H2A, H2B and H3 had already been described from Drosophila[2], from the sea urchin Parechinus angulosus[3] and from calf thymus [4,5], respectively. Since then, the numerous variants that have been described from these four basic protein families have been named in a variety of styles, using various combinations of numbers, letters and punctuation. The lack of systematized names can lead t
Nuclear Data Requirements for the Production Of Medical Isotopes in Fission Reactors and Particle Accelerators
M. A. Garland,R. E. Schenter,R. J. Talbert,S. G. Mashnik,W. B. Wilson
Physics , 1999,
Abstract: Through decades of effort in nuclear data development and simulations of reactor neutronics and accelerator transmutation, a collection of reaction data is continuing to evolve with the potential of direct applications to the production of medical isotopes. At Los Alamos the CINDER'90 code and library have been developed for nuclide inventory calculations using neutron-reaction (En < 20 MeV) and/or decay data for 3400 nuclides; coupled with the LAHET Code System (LCS), irradiations in neutron and proton environments below a few GeV are tractable; additional work with the European Activation File, the HMS-ALICE code and the reaction models of MCNPX (CEM95, BERTINI, or ISABEL with or without preequilibrium, evaporation and fission) have been used to produce evaluated reaction data for neutrons and protons to 1.7 GeV. At the Pacific Northwest National Laboratory, efforts have focused on production of medical isotopes and the identification of available neutron reaction data from results of integral measurements.
Caregiving in Alzheimer’s Disease: Research Designs & Considerations  [PDF]
Paul B. Arthur
Advances in Alzheimer's Disease (AAD) , 2018, DOI: 10.4236/aad.2018.72003
Abstract: Alzheimer’s disease and related dementias have made a considerable impact on society, and can take a significant toll on familial caregivers. Recent successful caregiving interventions suggest a promising future, though informed research design, a priori, is paramount in ensuring quality results that the Government and public may use to make informed policy and personal healthcare decisions. Research designs including basic science, randomized controlled trials (RCTs), qualitative, and quasi-experimental designs serve as the primary basis for discussion with literary examples and caveats.
Informal Caregiving for Persons with Chronic Conditions: Trends and Considerations  [PDF]
Paul B. Arthur
Advances in Aging Research (AAR) , 2018, DOI: 10.4236/aar.2018.74007
Abstract: Aging adults with chronic conditions rely heavily on an informal network of caregivers to remain within their communities of choice. This reliance can take a significant toll on caregivers through the lens of physical and psychological problems, financial issues, and social isolation. These variables may then lead to less desirable outcomes for care recipients. This review highlights existing support services in their many forms, including: psychosocial interventions, environmental interventions, respite care, and health information technology as a method of delivery. Given the current trend with informal caregivers assuming increased responsibility in healthcare, programs and services supporting these caregivers must be understood and trialed to ensure that their needs are not overlooked.
On the mechanics of motion and propagation in a binate frame
Samuel H. Talbert
Physics , 2011,
Abstract: Since clocks are not needed to observe many physical phenomena where light propagates among moving bodies, it should be possible to explain these observations without clock synchronization considerations. The paper provides such explanations. It uses a new type of reference system, a binate frame where all four coordinates of an event are physical distances. In a binate frame, familiar relativistic notions such as 'speed of light', 'time dilation', and 'Lorentz transformations' are not needed. We show that light's unique ability to propagate without material support endows the manifold of events with a non-diagonal metric of Lorentz signature. All our kinematical analyses of familiar phenomena then yield the results expected from Special Relativity. For dynamical analyses, we use a second form of Hamilton's principle, which obtains the usual canonical equations for the phase variables. And for electrodynamics applications, we employ the covariant form of Maxwell's equations, presented in binate-frame coordinatization.
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