Plasmid DNA replication and topology as visualized by two-dimensional agarose gel electrophoresis

31 p.- 12 fig.During the last 20 years, two-dimensional agarose gel electrophoresis combined with other techniques such as Polymerase Chain Reaction, helicase assay and electron microscopy, helped to characterize plasmid DNA replication and topology. Here we describe some of the most important findings that were made using this method including the characterization of uni-directional replication, replication origin interference, DNA breakage at the forks, replication fork blockage, replication knotting, replication fork reversal, the interplay of supercoiling and catenation and other changes in DNA topology that take place as replication progresses.This work was sustained in part by Grants # BIO2005-02224 and BFU2008-00408/BMC to J.B.S. and BFU2007-62670 to P.H. from the Spanish Ministerio de Ciencia e Innovación.Peer reviewe

Interplay of DNA supercoiling and catenation during the segregation of sister duplexes

The discrete regulation of supercoiling, catenation and knotting by DNA topoisomerases is well documented both in vivo and in vitro, but the interplay between them is still poorly understood. Here we studied DNA catenanes of bacterial plasmids arising as a result of DNA replication in Escherichia coli cells whose topoisomerase IV activity was inhibited. We combined high-resolution two-dimensional agarose gel electrophoresis with numerical simulations in order to better understand the relationship between the negative supercoiling of DNA generated by DNA gyrase and the DNA interlinking resulting from replication of circular DNA molecules. We showed that in those replication intermediates formed in vivo, catenation and negative supercoiling compete with each other. In interlinked molecules with high catenation numbers negative supercoiling is greatly limited. However, when interlinking decreases, as required for the segregation of newly replicated sister duplexes, their negative supercoiling increases. This observation indicates that negative supercoiling plays an active role during progressive decatenation of newly replicated DNA molecules in viv

Electrophoretic mobility of supercoiled, catenated and knotted DNA molecules

We systematically varied conditions of two-dimensional (2D) agarose gel electrophoresis to optimize separation of DNA topoisomers that differ either by the extent of knotting, the extent of catenation or the extent of supercoiling. To this aim we compared electrophoretic behavior of three different families of DNA topoisomers: (i) supercoiled DNA molecules, where supercoiling covered the range extending from covalently closed relaxed up to naturally supercoiled DNA molecules; (ii) postreplicative catenanes with catenation number increasing from 1 to ∼15, where both catenated rings were nicked; (iii) knotted but nicked DNA molecules with a naturally arising spectrum of knots. For better comparison, we studied topoisomer families where each member had the same total molecular mass. For knotted and supercoiled molecules, we analyzed dimeric plasmids whereas catenanes were composed of monomeric forms of the same plasmid. We observed that catenated, knotted and supercoiled families of topoisomers showed different reactions to changes of agarose concentration and voltage during electrophoresis. These differences permitted us to optimize conditions for their separation and shed light on physical characteristics of these different types of DNA topoisomers during electrophoresi

Unidad de Aprendizaje : Administración de Empresas

PROGRAMA DE LA UNIDAD DE APRENDIZAJE "ADMINISTRACIÓN DE EMPRESAS" DE LA LICENCIATURA EN RELACIONES ECONOMICAS INTERNACIONALES IMPARTIDA EN EL CENTRO UNIVERSITARIO UAEM TENANCING

Stingless bee keeping: Biocultural conservation and agroecological education

IntroductionStingless bee breeding, also called Meliponiculture, has existed for thousands of years in Mesoamerica among a variety of rural and indigenous cultures. Due to its biocultural importance, it represents a perfect device for agroecological education and scaling, as well as pollinator conservation. At the same time, promoting agroecological transitions are necessary for conserving the cultural heritage that meliponicultures represent.MethodsWe organized a series of activities based on this premise: documenting and dialoguing “saberes contemporáneos” (contemporary knowledges), design and implementation of community agroecological workshops, guided visits at the institutional Meliponary at ECOSUR Villahermosa and promotion of agroecological and biocultural school gardens, all in Tabasco, México. We used “diálogo de saberes” (knowledge dialogues) as a methodological approach, promoting respect for the contribution of the diversity of ontoepistemologies involved. We drew on the ideas of several pedagogues, mainly from popular education and critical pedagogy frameworks.Results and discussionWe identified characteristics of stingless bees and meliponicultures that make them excellent mediators for biocultural conservation and agroecological education: the complex, deep and beautiful relation between humans and bees; meliponiculture's ecological and cultural importance; stingless bees as pollinators par excellence, landscape connectors, and charismatic species; the association of bees with values around work and community; meliponicultures' symbolic relevance and emotional significance; meliponicultures as promoters of intergenerational dialogue; bee keeping as an activity of caring for the continuity of life; sensory stimulation through contact with colonies; learning through doing in the practice of beekeeping; meliponicultures as an activity requiring skill but no special equipment; and meliponiculture's productive potential. This confluence of teaching-learning opportunities, cultural and moral values, care for the land and biocultural diversity, and economic potential makes meliponiculture a potent catalyst for agroecological learning and transitions

Topo IV is the topoisomerase that knots and unknots sister duplexes during DNA replication

DNA topology plays a crucial role in all living cells. In prokaryotes, negative supercoiling is required to initiate replication and either negative or positive supercoiling assists decatenation. The role of DNA knots, however, remains a mystery. Knots are very harmful for cells if not removed efficiently, but DNA molecules become knotted in vivo. If knots are deleterious, why then does DNA become knotted? Here, we used classical genetics, high-resolution 2D agarose gel electrophoresis and atomic force microscopy to show that topoisomerase IV (Topo IV), one of the two type-II DNA topoisomerases in bacteria, is responsible for the knotting and unknotting of sister duplexes during DNA replication. We propose that when progression of the replication forks is impaired, sister duplexes become loosely intertwined. Under these conditions, Topo IV inadvertently makes the strand passages that lead to the formation of knots and removes them later on to allow their correct segregation

Innocampus Explora: Nuevas formas de comunicar ciencia

[EN] Innocampus Explora aims to show the students of the Burjassot-Paterna campus of the Universitat de València how the different scientific degrees are interrelated. To do this we propose activities in which students and teachers work together to cover the interdisciplinary nature of science, both in everyday and professional issues. Throughout this course the activities developed relate to new ways to communicate science. With the development of this project we contribute to a transversal quality education for all the participating students.[ES] Innocampus Explora tiene por objetivo mostrar a los estudiantes del campus de Burjassot-Paterna de la Universitat de València cómo los diferentes grados científicos están interrelacionados. Para ello proponemos actividades en las que estudiantes y profesores trabajen conjuntamente para abarcar la interdisciplinariedad de la ciencia, tanto en temas cotidianos como profesionales. A lo largo de este curso las actividades desarrolladas se relacionan con las nuevas formas de comunicar ciencia. Con el desarrollo de este proyecto contribuimos a una formación transversal de calidad para todos los estudiantes participantes.Moros Gregorio, J.; Rodrigo Martínez, P.; Torres Piedras, C.; Montoya Martínez, L.; Peña Peña, J.; Pla Díaz, M.; Galarza Jiménez, P.... (2019). Innocampus Explora: Nuevas formas de comunicar ciencia. En IN-RED 2019. V Congreso de Innovación Educativa y Docencia en Red. Editorial Universitat Politècnica de València. 814-823. https://doi.org/10.4995/INRED2019.2019.10449OCS81482

Clonal chromosomal mosaicism and loss of chromosome Y in elderly men increase vulnerability for SARS-CoV-2

The pandemic caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2, COVID-19) had an estimated overall case fatality ratio of 1.38% (pre-vaccination), being 53% higher in males and increasing exponentially with age. Among 9578 individuals diagnosed with COVID-19 in the SCOURGE study, we found 133 cases (1.42%) with detectable clonal mosaicism for chromosome alterations (mCA) and 226 males (5.08%) with acquired loss of chromosome Y (LOY). Individuals with clonal mosaic events (mCA and/or LOY) showed a 54% increase in the risk of COVID-19 lethality. LOY is associated with transcriptomic biomarkers of immune dysfunction, pro-coagulation activity and cardiovascular risk. Interferon-induced genes involved in the initial immune response to SARS-CoV-2 are also down-regulated in LOY. Thus, mCA and LOY underlie at least part of the sex-biased severity and mortality of COVID-19 in aging patients. Given its potential therapeutic and prognostic relevance, evaluation of clonal mosaicism should be implemented as biomarker of COVID-19 severity in elderly people. Among 9578 individuals diagnosed with COVID-19 in the SCOURGE study, individuals with clonal mosaic events (clonal mosaicism for chromosome alterations and/or loss of chromosome Y) showed an increased risk of COVID-19 lethality

VIII Encuentro de Docentes e Investigadores en Historia del Diseño, la Arquitectura y la Ciudad

Acta de congresoLa conmemoración de los cien años de la Reforma Universitaria de 1918 se presentó como una ocasión propicia para debatir el rol de la historia, la teoría y la crítica en la formación y en la práctica profesional de diseñadores, arquitectos y urbanistas. En ese marco el VIII Encuentro de Docentes e Investigadores en Historia del Diseño, la Arquitectura y la Ciudad constituyó un espacio de intercambio y reflexión cuya realización ha sido posible gracias a la colaboración entre Facultades de Arquitectura, Urbanismo y Diseño de la Universidad Nacional y la Facultad de Arquitectura de la Universidad Católica de Córdoba, contando además con la activa participación de mayoría de las Facultades, Centros e Institutos de Historia de la Arquitectura del país y la región. Orientado en su convocatoria tanto a docentes como a estudiantes de Arquitectura y Diseño Industrial de todos los niveles de la FAUD-UNC promovió el debate de ideas a partir de experiencias concretas en instancias tales como mesas temáticas de carácter interdisciplinario, que adoptaron la modalidad de presentación de ponencias, entre otras actividades. En el ámbito de VIII Encuentro, desarrollado en la sede Ciudad Universitaria de Córdoba, se desplegaron numerosas posiciones sobre la enseñanza, la investigación y la formación en historia, teoría y crítica del diseño, la arquitectura y la ciudad; sumándose el aporte realizado a través de sus respectivas conferencias de Ana Clarisa Agüero, Bibiana Cicutti, Fernando Aliata y Alberto Petrina. El conjunto de ponencias que se publican en este Repositorio de la UNC son el resultado de dos intensas jornadas de exposiciones, cuyos contenidos han posibilitado actualizar viejos dilemas y promover nuevos debates. El evento recibió el apoyo de las autoridades de la FAUD-UNC, en especial de la Secretaría de Investigación y de la Biblioteca de nuestra casa, como así también de la Facultad de Arquitectura de la UCC; va para todos ellos un especial agradecimiento