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A picornavirus protein interacts with Ran-GTPase and disrupts nucleocytoplasmic transport.

ABSTRACT: Active nucleocytoplasmic transport of protein and RNA in eukaryotes depends on the Ran-GTPase system to regulate cargo-receptor interactions. Several viruses, including the RNA picornaviruses, encode factors that alter nuclear transport with the aim of suppressing synthesis of antiviral factors and promoting viral replication. Picornaviruses in the cardiovirus genus express a unique 67-aa Leader protein (L), known to alter the subcellular distribution of IFN regulatory proteins targeted to the nucleus. We report here that L binds directly to Ran and blocks nuclear export of new mRNAs. In Xenopus egg extracts, recombinant L also inhibits mitotic spindle assembly, a RanGTP function crucial to cell-cycle progression. We propose that L inhibits nucleocytoplasmic transport during infection by disrupting the RanGDP/GTP gradient. This inhibition triggers an efflux of nuclear proteins necessary for viral replication and causes IFN suppression. To our knowledge, L is the first viral picornaviral protein to interact directly with Ran and modulate the Ran-dependent nucleocytoplasmic pathway.

SUBMITTER: Porter FW

PROVIDER: S-EPMC1567894 | biostudies-literature | 2006 Aug

REPOSITORIES: biostudies-literature

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A picornavirus protein interacts with Ran-GTPase and disrupts nucleocytoplasmic transport.

Porter Frederick W FW Bochkov Yury A YA Albee Alison J AJ Wiese Christiane C Palmenberg Ann C AC

Proceedings of the National Academy of Sciences of the United States of America 20060803 33

Active nucleocytoplasmic transport of protein and RNA in eukaryotes depends on the Ran-GTPase system to regulate cargo-receptor interactions. Several viruses, including the RNA picornaviruses, encode factors that alter nuclear transport with the aim of suppressing synthesis of antiviral factors and promoting viral replication. Picornaviruses in the cardiovirus genus express a unique 67-aa Leader protein (L), known to alter the subcellular distribution of IFN regulatory proteins targeted to the n ...[more]

PMID: 16888036

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Project description:RNA viruses that replicate in the cytoplasm often disrupt nucleocytoplasmic transport to preferentially translate their own transcripts and prevent host antiviral responses. The Sarbecovirus accessory protein ORF6 has previously been shown to be a major inhibitor of interferon production in both severe acute respiratory syndrome coronavirus (SARS-CoV) and severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). Here, we show SARS-CoV-2-infected cells display an elevated level of nuclear mRNA accumulation compared to mock-infected cells. We demonstrate that ORF6 is responsible for this nuclear imprisonment of host mRNA, and using a cotransfected reporter assay, we show this nuclear retention of mRNA blocks expression of newly transcribed mRNAs. ORF6's nuclear entrapment of host mRNA is associated with its ability to copurify with the mRNA export factors, Rae1 and Nup98. These protein-protein interactions map to the C terminus of ORF6 and can be abolished by a single amino acid mutation in Met58. Overexpression of Rae1 restores reporter expression in the presence of SARS-CoV-2 ORF6. SARS-CoV ORF6 also interacts with Rae1 and Nup98. However, SARS-CoV-2 ORF6 more strongly copurifies with Rae1 and Nup98 and results in significantly reduced expression of reporter proteins compared to SARS-CoV ORF6, a potential mechanism for the delayed symptom onset and presymptomatic transmission uniquely associated with the SARS-CoV-2 pandemic. We also show that both SARS-CoV and SARS-CoV-2 ORF6 block nuclear import of a broad range of host proteins. Together, these data support a model in which ORF6 clogs the nuclear pore through its interactions with Rae1 and Nup98 to prevent both nuclear import and export, rendering host cells incapable of responding to SARS-CoV-2 infection.IMPORTANCE SARS-CoV-2, the causative agent of coronavirus disease 2019 (COVID-19), is an RNA virus with a large genome that encodes multiple accessory proteins. While these accessory proteins are not required for growth in vitro, they can contribute to the pathogenicity of the virus. We demonstrate that SARS-CoV-2-infected cells accumulate poly(A) mRNA in the nucleus, which is attributed to the accessory protein ORF6. Nuclear entrapment of mRNA and reduced expression of newly transcribed reporter proteins are associated with ORF6's interactions with the mRNA export proteins Rae1 and Nup98. SARS-CoV ORF6 also shows the same interactions with Rae1 and Nup98. However, SARS-CoV-2 ORF6 more strongly represses reporter expression and copurifies with Rae1 and Nup98 compared to SARS-CoV ORF6. Both SARS-CoV ORF6 and SARS-CoV-2 ORF6 block nuclear import of a wide range of host factors through interactions with Rae1 and Nup98. Together, our results suggest ORF6's disruption of nucleocytoplasmic transport prevents infected cells from responding to the invading virus.

Dataset Information

A picornavirus protein interacts with Ran-GTPase and disrupts nucleocytoplasmic transport.

Publications

A picornavirus protein interacts with Ran-GTPase and disrupts nucleocytoplasmic transport.

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