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La latencia celular inducida por Cas13 previene el surgimiento de bacteriófagos resistentes a CRISPR
Alexander J Meeske1, Sandra Nakandakari-Higa2, Luciano A Marraffini3,4
1Laboratory of Bacteriology, The Rockefeller University, New York, NY, USA. ameeske@rockefeller.edu.
Nature
|May 31, 2019
Resumen
La enzima Cas13, un sistema CRISPR de tipo VI, se defiende contra los fagos de ADN mediante la escisión de las transcripciones de las células huésped. Esta división trans detiene la replicación de los fagos, protege a las bacterias y previene la aparición de fagos resistentes.
Área de la Ciencia:
- Microbiología
- Biología molecular
- La genética
Sus antecedentes:
- Los sistemas de repetición palíndroma corta (CRISPR) agrupados y regularmente espaciados utilizan ARN CRISPR (crRNA) para guiar a las nucleasas (Cas) asociadas a CRISPR para la orientación de ácidos nucleicos extraños.
- Los sistemas CRISPR de tipo VI, específicamente la nucleasa Cas13, utilizan guías de ARN para dividir moléculas de ARN.
- Si bien Cas13 es conocido por la escisión del ARN, su papel en la defensa contra los fagos de ADN de doble cadena (dsDNA) sigue sin estar claro.
Objetivo del estudio:
- Investigar el mecanismo por el cual Cas13 se defiende contra los fagos de ADNd.
- Determinar si las actividades de escisión de cis y/o trans ARN de Cas13 están implicadas en la defensa de los fagos.
- Comprender cómo el Cas13 confiere inmunidad contra los fagos, incluidos los resistentes a los sistemas CRISPR dirigidos al ADN.
Principales métodos:
- Investigación experimental de la actividad de Cas13 en la defensa bacteriana contra los fagos dsDNA.
- Análisis de las funciones de escisión del ARN cis y trans de Cas13 durante la infección de los fagos.
- Evaluación de la neutralización de los fagos y de la inmunidad del huésped conferida por la activación de Cas13.
Principales resultados:
- La transcisión mediada por Cas13 de las transcripciones celulares del huésped es suficiente para detener el crecimiento del fago y abortar el ciclo infeccioso.
- Esta actividad de trans-clivado agota la población de fagos y confiere inmunidad de grupo a las bacterias no infectadas.
- Cas13 neutraliza eficazmente los fagos, incluso aquellos con mutaciones que evaden los sistemas CRISPR de orientación del ADN, al dirigirse a las transcripciones del huésped.
Conclusiones:
- Los sistemas CRISPR de tipo VI, a través de la actividad de escisión transversal de Cas13 en las transcripciones del huésped, proporcionan una defensa robusta contra los fagos dsDNA.
- Este mecanismo actúa sobre la célula huésped, no directamente sobre el fago, ofreciendo una amplia protección.
- La defensa mediada por Cas13 previene la aparición de fagos resistentes a CRISPR y mitiga los brotes de fagos.
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