RESUMEN
Many viruses shut off host gene expression to inhibit antiviral responses. Viral proteins and host proteins required for viral replication are typically spared in this process, but the mechanisms of target selectivity during host shutoff remain poorly understood. Using transcriptome-wide and targeted reporter experiments, we demonstrate that the influenza A virus endoribonuclease PA-X usurps RNA splicing to selectively target host RNAs for destruction. Proximity-labeling proteomics reveals that PA-X interacts with cellular RNA processing proteins, some of which are partially required for host shutoff. Thus, PA-X taps into host nuclear pre-mRNA processing mechanisms to destroy nascent mRNAs shortly after their synthesis. This mechanism sets PA-X apart from other viral host shutoff proteins that target actively translating mRNAs in the cytoplasm. Our study reveals a unique mechanism of host shutoff that helps us understand how influenza viruses suppress host gene expression.
Asunto(s)
Virus de la Influenza A/fisiología , Empalme del ARN , ARN Mensajero/metabolismo , Proteínas Represoras/metabolismo , Proteínas no Estructurales Virales/metabolismo , Células A549 , Factor de Especificidad de Desdoblamiento y Poliadenilación/antagonistas & inhibidores , Factor de Especificidad de Desdoblamiento y Poliadenilación/genética , Factor de Especificidad de Desdoblamiento y Poliadenilación/metabolismo , Regulación hacia Abajo , Endorribonucleasas/metabolismo , Células HEK293 , Interacciones Huésped-Patógeno , Humanos , Interferones/genética , Interferones/metabolismo , Mutagénesis Sitio-Dirigida , Interferencia de ARN , Precursores del ARN/metabolismo , Sitios de Empalme de ARN , ARN Interferente Pequeño/metabolismo , Proteínas Represoras/genética , Regulación hacia Arriba , Proteínas no Estructurales Virales/genética , Factores de Escisión y Poliadenilación de ARNm/antagonistas & inhibidores , Factores de Escisión y Poliadenilación de ARNm/genética , Factores de Escisión y Poliadenilación de ARNm/metabolismoRESUMEN
The ability to shut off host gene expression is a shared feature of many viral infections, and it is thought to promote viral replication by freeing host cell machinery and blocking immune responses. Despite the molecular differences between viruses, an emerging theme in the study of host shutoff is that divergent viruses use similar mechanisms to enact host shutoff. Moreover, even viruses that encode few proteins often have multiple mechanisms to affect host gene expression, and we are only starting to understand how these mechanisms are integrated. In this review we discuss the multiplicity of host shutoff mechanisms used by the orthomyxovirus influenza A virus and members of the alpha- and gamma-herpesvirus subfamilies. We highlight the surprising similarities in their mechanisms of host shutoff and discuss how the different mechanisms they use may play a coordinated role in gene regulation.
