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Arginine methylation enhances the RNA chaperone activity of the West Nile virus host factor AUF1 p45.

ABSTRACT: A prerequisite for the intracellular replication process of the Flavivirus West Nile virus (WNV) is the cyclization of the viral RNA genome, which enables the viral replicase to initiate RNA synthesis. Our earlier studies indicated that the p45 isoform of the cellular AU-rich element binding protein 1 (AUF1) has an RNA chaperone activity, which supports RNA cyclization and viral RNA synthesis by destabilizing a stem structure at the WNV RNA's 3'-end. Here we show that in mammalian cells, AUF1 p45 is consistently modified by arginine methylation of its C terminus. By a combination of different experimental approaches, we can demonstrate that the methyltransferase PRMT1 is necessary and sufficient for AUF1 p45 methylation and that PRMT1 is required for efficient WNV replication. Interestingly, in comparison to the nonmethylated AUF1 p45, the methylated AUF1 p45(aDMA) exhibits a significantly increased affinity to the WNV RNA termini. Further data also revealed that the RNA chaperone activity of AUF1 p45(aDMA) is improved and the methylated protein stimulates viral RNA synthesis considerably more efficiently than the nonmethylated AUF1 p45. In addition to its destabilizing RNA chaperone activity, we identified an RNA annealing activity of AUF1 p45, which is not affected by methylation. Arginine methylation of AUF1 p45 thus represents a specific determinant of its RNA chaperone activity while functioning as a WNV host factor. Our data suggest that the methylation modifies the conformation of AUF1 p45 and in this way affects its RNA binding and restructuring activities.

SUBMITTER: Friedrich S

PROVIDER: S-EPMC5029455 | biostudies-literature | 2016 Oct

REPOSITORIES: biostudies-literature

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Arginine methylation enhances the RNA chaperone activity of the West Nile virus host factor AUF1 p45.

Friedrich Susann S Schmidt Tobias T Schierhorn Angelika A Lilie Hauke H Szczepankiewicz Grit G Bergs Sandra S Liebert Uwe G UG Golbik Ralph P RP Behrens Sven-Erik SE

RNA (New York, N.Y.) 20160812 10

A prerequisite for the intracellular replication process of the Flavivirus West Nile virus (WNV) is the cyclization of the viral RNA genome, which enables the viral replicase to initiate RNA synthesis. Our earlier studies indicated that the p45 isoform of the cellular AU-rich element binding protein 1 (AUF1) has an RNA chaperone activity, which supports RNA cyclization and viral RNA synthesis by destabilizing a stem structure at the WNV RNA's 3'-end. Here we show that in mammalian cells, AUF1 p4 ...[more]

PMID: 27520967

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Project description:In previous studies, we showed that the cellular RNA-binding protein AUF1 supports the replication process of the flavivirus West Nile virus. Here we demonstrate that the protein also enables effective proliferation of dengue virus and Zika virus, indicating that AUF1 is a general flavivirus host factor. Further studies demonstrated that the AUF1 isoform p45 significantly stimulates the initiation of viral RNA replication and that the protein's RNA chaperone activity enhances the interactions of the viral 5'UAR and 3'UAR genome cyclization sequences. Most interestingly, we observed that AUF1 p45 destabilizes not only the 3'-terminal stem-loop (3'SL) but also 5'-terminal stem-loop B (SLB) of the viral genome. RNA structure analyses revealed that AUF1 p45 increases the accessibility of defined nucleotides within the 3'SL and SLB and, in this way, exposes both UAR cyclization elements. Conversely, AUF1 p45 does not modulate the fold of stem-loop A (SLA) at the immediate genomic 5' end, which is proposed to function as a promoter of the viral RNA-dependent RNA polymerase (RdRp). These findings suggest that AUF1 p45, by destabilizing specific stem-loop structures within the 5' and 3' ends of the flaviviral genome, assists genome cyclization and concurrently enables the RdRp to initiate RNA synthesis. Our study thus highlights the role of a cellular RNA-binding protein inducing a flaviviral RNA switch that is crucial for viral replication.IMPORTANCE The genus Flavivirus within the Flaviviridae family includes important human pathogens, such as dengue, West Nile, and Zika viruses. The initiation of replication of the flaviviral RNA genome requires a transformation from a linear to a cyclized form. This involves considerable structural reorganization of several RNA motifs at the genomic 5' and 3' ends. Specifically, it needs a melting of stem structures to expose complementary 5' and 3' cyclization elements to enable their annealing during cyclization. Here we show that a cellular RNA chaperone, AUF1 p45, which supports the replication of all three aforementioned flaviviruses, specifically rearranges stem structures at both ends of the viral genome and in this way permits 5'-3' interactions of cyclization elements. Thus, AUF1 p45 triggers the RNA switch in the flaviviral genome that is crucial for viral replication. These findings represent an important example of how cellular (host) factors promote the propagation of RNA viruses.

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Arginine methylation enhances the RNA chaperone activity of the West Nile virus host factor AUF1 p45.

Publications

Arginine methylation enhances the RNA chaperone activity of the West Nile virus host factor AUF1 p45.

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