- Nace la plataforma Bioimagen, un proyecto que aúna las múltiples capacidades del CNB en el campo de la microscopía.
- El programa de Excelencia Severo Ochoa, clave para establecer la nueva plataforma de Bioimagen en el CNB.
Gracias al apoyo del programa de Excelencia Severo Ochoa, el Centro Nacional de Biotecnología (CNB-CSIC) ha sido capaz de fortalecer las infraestructuras de microscopía disponibles en el centro. La adquisición de nuevos equipos como microscopios ópticos avanzados y electrónicos de alta resolución van a permitir implementar nuevos enfoques utilizando técnicas de microscopía integradora y correlativa. De esta forma, se podrá abarcar un mayor rango de escalas y resoluciones múltiples, desde la anatomía macroscópica hasta el nivel unicelular, molecular y atómico. La estrecha colaboración entre los servicios de microscopia óptica avanzada, microscopía y criomocroscopía electrónica servirá de sinergia para el desarrollo de nuevas técnicas de microscopía correlativa en el CNB.
La nueva Unidad de Análisis de Datos de Bioimagen servirá para resolver los desafíos matemáticos necesarios para el procesamiento de datos procedentes de experimentos de imágenes de molécula única, microscopía óptica y electrónica. Además, el Centro de procesamiento de imágenes criogénicas de Instruct, la única instalación española perteneciente a INSTRUCT, la red europea de instalaciones de biología estructural, brinda apoyo continuo al procesamiento de datos de criomicroscopía.
Los plásmidos son moléculas de ADN circulares presentes en bacterias que se replican (duplican) de forma independiente del cromosoma bacteriano. La transmisión de plásmidos entre bacterias puede suponer la ganancia o la perdida de una función determinada en la célula receptora. Por ejemplo, algunos genes contenidos en plásmidos son capaces de conferir resistencia a antibióticos, y la transmisión de estos genes puede ser beneficiosa para la supervivencia bacteriana, ya que se convertirán en resistentes a esos antibióticos.
El sistema más habitual de duplicación de estos plásmidos se llama replicación por circulo rodante (RCR). Este proceso requiere la unión de la proteína Rep a una secuencia determinada del ADN, el corte de una de las cadenas del ADN y la separación de la doble cadena a medida que la helicasa PcrA se mueve por una de ellas. Sin embargo, el mecanismo por el cual se inicia la replicación y se desenrolla la doble hélice del ADN no se conoce con detalle.
Investigadores del Centro Nacional de Biotecnología, en colaboración con un grupo de científicos de la Universidad de Pittsburgh (Estados Unidos) han sido capaces de observar a nivel molecular la interacción de las proteínas Rep y PcrA en el proceso de replicación de plásmidos portadores de genes de resistencia a antibióticos.
Nucleic Acids Res. 2020 Jan 13. pii: gkz1200.
Carrasco C, Pastrana CL, Aicart-Ramos C, Leuba SH, Khan SA, Moreno-Herrero F.
Abstract
The rolling-circle replication is the most common mechanism for the replication of small plasmids carrying antibiotic resistance genes in Gram-positive bacteria. It is initiated by the binding and nicking of double-stranded origin of replication by a replication initiator protein (Rep). Duplex unwinding is then performed by the PcrA helicase, whose processivity is critically promoted by its interaction with Rep. How Rep and PcrA proteins interact to nick and unwind the duplex is not fully understood. Here, we have used magnetic tweezers to monitor PcrA helicase unwinding and its relationship with the nicking activity of Staphylococcus aureus plasmid pT181 initiator RepC. Our results indicate that PcrA is a highly processive helicase prone to stochastic pausing, resulting in average translocation rates of 30 bp s-1, while a typical velocity of 50 bp s-1 is found in the absence of pausing. Single-strand DNA binding protein did not affect PcrA translocation velocity but slightly increased its processivity. Analysis of the degree of DNA supercoiling required for RepC nicking, and the time between RepC nicking and DNA unwinding, suggests that RepC and PcrA form a protein complex on the DNA binding site before nicking. A comprehensive model that rationalizes these findings is presented.
doi: 10.1093/nar/gkz1200.
- The results of the study published in eLife help to understand how DNA is organised during cell division in Bacillus subtilis.
During cell division, DNA condensates to assure a proper distribution of the genetic material but the mechanism is not fully understood. An international study led by researchers from the National Centre of Biotechnology (CNB-CSIC) reveals the role of ParB, a protein responsible for chromosome organization of the chromosome during cell division in DNA condensation in Bacillus subtilis.
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