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. 2023 Jan 11;21(3):178–194. doi: 10.1038/s41579-022-00839-1

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© Springer Nature Limited 2023, Springer Nature or its licensor (e.g. a society or other partner) holds exclusive rights to this article under a publishing agreement with the author(s) or other rightsholder(s); author self-archiving of the accepted manuscript version of this article is solely governed by the terms of such publishing agreement and applicable law.

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Fig. 3 — Cellular induction of an antiviral response is dependent on bidirectional trafficking through the nuclear pore complex (NPC). With the aid of nuclear transport receptors (importins), cellular transcription factors that are induced in response to infection translocate through the NPC into the nucleus and bind sequences within antiviral genes to drive their expression. Following de novo transcription and capping of the nascent messenger RNA (mRNA), the host spliceosome assembles at RNA splicing sites and promotes intron excision to yield translationally competent mature transcripts. These transcripts associate with nuclear transport receptors (exportins) and are exported through the NPC into the cytoplasm, where they are translated by host ribosomes and routed for proper folding and cellular localization based on recognition of their signal peptide by the signal recognition particle (SRP). SARS-CoV-2 encodes several proteins that block nuclear transport (depicted in purple), including non-structural proteins (Nsps), the open reading frame 6 (ORF6) accessory protein and the membrane structural protein (M). This inhibition is facilitated by interactions with the host proteins indicated (KPNA2, karyopherin subunit α2; KPNA6, karyopherin subunit α6; NTF2, nuclear transport factor 2; Nup62, nucleoporin 62; Nup98, nucleoporin 98; NXF1, nuclear RNA export factor 1; NXT1, nuclear transport factor 2-like export factor 1; Rae1, ribonucleic acid export factor 1). SARS-CoV-2 also encodes proteins that ultimately shut off translation (depicted in red) by inhibiting host RNA splicing, preferentially blocking host RNAs for nuclear export in favour of viral RNAs, interfering with ribosomal function and preventing protein trafficking. As Nsp1 is also capable of more generally inhibiting protein synthesis, its role in preferential targeting of viral RNAs remains uncertain (question marks).