1,720,956 research outputs found
Sequence-dependent mobility of telomeric nucleosomes
No full textNucleosome mobilization plays a relevant role in regulating the accessibility of DNA in chromatin. A class of enzymes known as ATP-dependent chromatin remodeling complexes has been isolated that actively alter nucleosome positioning. Nucleosomes possess also a certain degree of inherent mobility that is likely to depend on DNA sequence. Both processes contribute to facilitate the access of regulatory factors to their binding sites.
The structure of human telomeres is not yet completely characterized. Several proteins involved in the formation of the human telomeric complex have been identified, such as hTRF1 and hTRF2 which bind to GGGTAA duplex telomeric repeats. Nevertheless, most human telomeric DNA is organized into tightly spaced nucleosomes. Due to the peculiar features of telomeric repeated sequences, telomeric nucleosomes are less stable than bulk nucleosomes and occupy multiple isoenergetic positions spaced every telomere repeat. The emerging view is that telomeres are extremely dynamic structures whose organization and function change throughout the cell cycle. Since hTRF proteins and the histone octamer compete for telomeric DNA, to understand telomere dynamics it is clearly important to understand the interphase between regular chromatin and telomere structure, or more specifically the ability of nucleosomes to move along DNA and how proteins recognize their binding sites on nucleosomes.
Using an in vitro model system, we have analyzed telomeric nucleosome mobility as a function of temperature and ionic strength. We found that nucleosomes formed on telomeric sequences are significatively more mobile than bulk nucleosomes. Moreover, we found that hTRF1 and hTRF2 are able to specifically recognize their binding sites in a nucleosomal context. Experiments are in progress to examine if binding of hTRF proteins could induce nucleosome mobilization or dissociation
I servizi universitari per tutti. Giornata in onore di Edoardo Arslan
No full textIl Centro di Servizi e Ricerca per la Disabilità, la Riabilitazione e l'Integrazione dell’Università degli Studi di Padova, diretto dalla prof.ssa Laura Nota, ha organizzato una giornata in onore del Prof. Edoardo Arslan, che si terrà giovedì 1° ottobre p.v.alle ore 9,30 a Padova presso la Scuola di Psicologia in via Venezia 12. La giornata sarà centrata sul tema "I servizi universitari per tutti", ricordando il grande impegno sui temi della disabilità profuso dal prof. Arslan, ininterrottamente, dai primi anni ’90 al 2013, ricoprendo inoltre il ruolo di Delegato a rappresentare il Rettore per i problemi della disabilità nell'Università, fino al momento della prematura scomparsa
Telomeric nucleosomes: mobility free from constraints
No full textTelomeres are the specialized nucleoprotein structures that protect the ends of eukaryotic chromosomes. In higher eukaryotes, telomeres are organized in nucleosomal arrays, with an unusual shorter spacing than bulk chromatin. Electron microscopy visualizations by Nikitina and Woodcock showed that both t-loops and adjacent telomeric domains are organized in nucleosomal arrays. Moreover, telomeres are highly dynamic structures whose organization and function change throughout the cell cycle. Telomeric double stranded DNA is specifically recognized by two proteins TRF1 and TRF2. Little is known about the involvement of telomeric nucleosomes in the establishment of higher order telomere structures.
Whether histones and specific telomeric proteins compete for telomeric DNA binding (and hence occupy different telomere domains) or whether nucleosomes are directly involved in the formation of the telomeric complex is a relevant issue in order to understand telomeric structure and its dynamics.
To address these questions, we have studied the telomeric nucleosomal arrays organization by an in vitro system that mimic telomeric chromatin, and set up a model system to study sequence-dependent intrinsic nucleosome mobility
Specific interactions with intra- and intermolecular G-quadruplex DNA structures by hydrosoluble coronene derivatives: A new class of telomerase inhibitors
No full textIn developing G-quadruplex interactive telomerase inhibitors two main features have to be taken into account: the hydrophobic interactions with the G-quartet plane and the electrostatic interactions with the negatively charged phosphates of the four grooves. In this paper, we report the synthesis of four hydrosoluble coronene derivatives, which are characterized by a large hydrophobic aromatic core and four orthogonal hydrophilic side chains. We have studied their ability to induce both inter- and intramolecular G-quadruplex structures and found a significant selectivity of all the coronene derivatives for the intramolecular G-quadruplex. The efficiency in inhibiting human telomerase has been evaluated in a cell-free system and the experimental results correlate with the relative affinities of these compounds for the G-quadruplex monomeric structure, as derived by molecular modelling simulations. Thus, the coronene derivatives can be considered as a new class of telomerase inhibitors, although further investigations are surely necessary to fully exploit their features. (c) 2006 Elsevier Ltd. All rights reserved
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
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
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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