Referencia

Brissett NC, Martin MJ, Pitcher RS, Bianchi J, Juarez R, Green AJ, Fox GC, Blanco L, Doherty AJ. Mol Cell. 2011 Jan 21;41(2):221-31.

Autores

Nigel C. Brissett*, Maria Jose Martin*, Robert S. Pitcher, Julie Bianchi, Raquel Juarez, Andrew J. Green, Gavin C. Fox, Luis Blanco', and Aidan J. Doherty'. (* coauthors) ('co-corresponding authors)

Resumen

Grapando el ADN roto de la bacteria de la tuberculosis: Investigadores del Centro de Biología Molecular “Severo Ochoa” CBMSO (CSIC-UAM) llevan más de 10 años investigando sobre las proteínas implicadas en un importante mecanismo celular: el que repara las roturas de la doble hélice de ADN. En una investigación reciente, revelan nueva información sobre la manera como opera este mecanismo en la bacteria causante de la tuberculosis. La investigación, publicada en la revista Molecular Cell, ofrece una nueva visión sobre la reparación del ADN en bacterias y promete abrir puertas a nuevas formas de terapia contra estos agentes patógenos.

Descripción

In many prokaryotes, a specific DNA primase/polymerase (PolDom) is required for nonhomologous end joining (NHEJ) repair of DNA double-strand breaks (DSBs). Here,wereport the crystal structure of a catalytically active conformation of Mycobacterium tuberculosis PolDom, consisting of a polymerase bound to a DNA end with a 30 overhang, two metal ions, and an incoming nucleotide but, significantly, lacking a primer strand. This structure represents a polymerase:DNA complex in a preternary intermediate state. This polymerase complex occurs in solution, stabilizing the enzyme on DNA ends and promoting nucleotide extension of short incoming termini. We also demonstrate that the invariant Arg220, contained in a conserved loop (loop 2), plays an essential role in catalysis by regulating binding of a second metal ion in the active site. We propose that this NHEJ intermediate facilitates extension reactions involving critically short or noncomplementary DNA ends, thus promoting break repair and minimizing sequence loss during DSB repair.


Imágen artículo Abril

REFERENCIA DEL GRUPO E INVESTIGADOR
El laboratorio del Profesor Luis Blanco está especializado en el estudio de las únicas dos DNA polimerasas implicadas en la reparación de roturas de doble cadena (DSBs) en humanos, Pol lambda y Pol mu, identificadas en el laboratorio en 1999. Estas enzimas son relevantes para el mantenimiento del equilibro entre la estabilidad genómica y los niveles de variabilidad requeridos, no sólo para la evolución, sino para el normal funcionamiento de genes específicos. Una mala regulación de estos enzimas puede ser responsable de fenotipos mutadores asociados a carcinogénesis, como hemos demostrado recientemente para una variante polimórfica de Pol lambda, asociada a cáncer colorrectal. Datos recientes, en colaboración con M.A. Rodriguez Marcos (CBMSO, Madrid), indican que Pol mu, por su parte, es esencial para el desarrollo del sistema inmune del embrión. En colaboración con A. Doherty (Univ. Sussex, UK), hemos mostrado que algunas bacterias, tales como Mycobacterium tuberculosis, tienen un sistema muy eficiente de reparación de DSBs, basado en una ligasa multifuncional que contiene dominios con actividad nucleasa y polimerasa. Hemos encontrado interesantes paralelismos entre estos enzimas y Pol mu, siendo los primeros en resolver la estructura 3D del paso de sinapsis asociado a la reparación por reunión de extremos no homólogos (NHEJ) de una DSB.

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