Functions of NSPs encoded by ORF1a and 1b of SARS-CoV-2
| NSP proteins | Possible biological functions | References |
|---|---|---|
| Nsp1 | Inhibit translation of host proteins through r-mRNA binding | [5–8] |
| Nsp2 | Disruption of host cell environment by binding with prohibitin-1 and 2 | [6–8] |
| Nsp3 (a PLpro), largest nsp with 1,299 aa) | Viral polyprotein processing | [6–8] |
| Nsp4 | Viral replication and formation of transcription complexes | [6–8] |
| Nsp5 | Viral polyprotein processing | [6–8] |
| Nsp6 (a 3C-like protease) | Viral replication and formation of transcription complexes, biogenesis of replication organelle | [6, 7, 9] |
| Nsp7 | Accessory factors of RdRP, stabilization of the replication/transcription complex, SARS-CoV nsp7 enhances RNA binding by nsp8 | [6–8] |
| Nsp8 | Accessory factors of RdRP, stabilization of the replication/transcription complex | [6–8] |
| Complex formed between Nsp7+8 nsp(7+8) | It is a unique multimeric RNA polymerase capable of both de novo initiation and primer extension activity, and is an accessory factor for RdRP | [6–8] |
| Nsp9 | RNA-binding protein | [6–8, 10, 11] |
| Nsp10 | Cofactor of nsp14 and nsp16, Nsp14−Nsp10 complex enhances translation inhibition, which is executed by NSP14 consequently abolishing the IFN-I-dependent induction of ISGs | [6–8, 12] |
| Nsp11 (smallest nsp with 13 aa) | Intrinsically disordered protein with unknown function | [6–9, 12, 13] |
| Nsp12 | It is an RdRP in addition to being a nucleotidyl-transferase | [6, 7, 13] |
| Nsp13 | It is a helicase with a possible function in nucleic acid metabolism including DNA replication, recombination, transcription, repair, ribosome biogenesis, RNA processing, translation, and decay | [6–8, 13] |
| Nsp14 | It is a proofreading 3’–5’ exoribonuclease and a guanosine-N7 methyltransferase (N7-MTase) for the RNA cap formation, effects of viral infection on the host cell transcriptome, Nsp14−Nsp10 complex enhances translation inhibition, which is executed by NSP14 consequently abolishing the IFN-I-dependent induction of ISGs | [6–8, 12, 13] |
| Nsp15 and 16 | Nsp15 is a uridine-specific endoribonuclease and IFN antagonist, whereas the Nsp16 is ribose 2′-O-methyltransferase for gRNA cap formation | [6–8, 12, 13] |
aa: amino acids; RdRP: RNA-dependent RNA polymerase; ISGs: IFN stimulated genes; gRNA: genomic RNA; mRNA: messenger RNA; r-mRNA: ribosomal-mRNA
