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Crystal Structure of SARS-CoV-2 NSP7-NSP8 complex.
Structural highlights
FunctionR1AB_SARS2 Multifunctional protein involved in the transcription and replication of viral RNAs. Contains the proteinases responsible for the cleavages of the polyprotein.[UniProtKB:P0C6X7] Inhibits host translation by interacting with the 40S ribosomal subunit. The nsp1-40S ribosome complex further induces an endonucleolytic cleavage near the 5'UTR of host mRNAs, targeting them for degradation. Viral mRNAs are not susceptible to nsp1-mediated endonucleolytic RNA cleavage thanks to the presence of a 5'-end leader sequence and are therefore protected from degradation. By suppressing host gene expression, nsp1 facilitates efficient viral gene expression in infected cells and evasion from host immune response.[UniProtKB:P0C6X7] May play a role in the modulation of host cell survival signaling pathway by interacting with host PHB and PHB2. Indeed, these two proteins play a role in maintaining the functional integrity of the mitochondria and protecting cells from various stresses.[UniProtKB:P0C6X7] Responsible for the cleavages located at the N-terminus of the replicase polyprotein. In addition, PL-PRO possesses a deubiquitinating/deISGylating activity and processes both 'Lys-48'- and 'Lys-63'-linked polyubiquitin chains from cellular substrates. Participates together with nsp4 in the assembly of virally-induced cytoplasmic double-membrane vesicles necessary for viral replication. Antagonizes innate immune induction of type I interferon by blocking the phosphorylation, dimerization and subsequent nuclear translocation of host IRF3. Prevents also host NF-kappa-B signaling.[UniProtKB:P0C6X7] Participates in the assembly of virally-induced cytoplasmic double-membrane vesicles necessary for viral replication.[UniProtKB:P0C6X7] Cleaves the C-terminus of replicase polyprotein at 11 sites. Recognizes substrates containing the core sequence [ILMVF]-Q-|-[SGACN] (PubMed:32198291). Also able to bind an ADP-ribose-1-phosphate (ADRP).[UniProtKB:P0C6X7][1] Plays a role in the initial induction of autophagosomes from host reticulum endoplasmic. Later, limits the expansion of these phagosomes that are no longer able to deliver viral components to lysosomes.[UniProtKB:P0C6X7] Forms a hexadecamer with nsp8 (8 subunits of each) that may participate in viral replication by acting as a primase. Alternatively, may synthesize substantially longer products than oligonucleotide primers.[UniProtKB:P0C6X7] Forms a hexadecamer with nsp7 (8 subunits of each) that may participate in viral replication by acting as a primase. Alternatively, may synthesize substantially longer products than oligonucleotide primers.[UniProtKB:P0C6X7] May participate in viral replication by acting as a ssRNA-binding protein.[UniProtKB:P0C6X7] Plays a pivotal role in viral transcription by stimulating both nsp14 3'-5' exoribonuclease and nsp16 2'-O-methyltransferase activities. Therefore plays an essential role in viral mRNAs cap methylation.[UniProtKB:P0C6X7] Responsible for replication and transcription of the viral RNA genome.[UniProtKB:P0C6X7] Multi-functional protein with a zinc-binding domain in N-terminus displaying RNA and DNA duplex-unwinding activities with 5' to 3' polarity. Activity of helicase is dependent on magnesium.[UniProtKB:P0C6X7] Enzyme possessing two different activities: an exoribonuclease activity acting on both ssRNA and dsRNA in a 3' to 5' direction and a N7-guanine methyltransferase activity. Acts as a proofreading exoribonuclease for RNA replication, thereby lowering The sensitivity of the virus to RNA mutagens.[UniProtKB:P0C6X7] Mn(2+)-dependent, uridylate-specific enzyme, which leaves 2'-3'-cyclic phosphates 5' to the cleaved bond.[UniProtKB:P0C6X7] Methyltransferase that mediates mRNA cap 2'-O-ribose methylation to the 5'-cap structure of viral mRNAs. N7-methyl guanosine cap is a prerequisite for binding of nsp16. Therefore plays an essential role in viral mRNAs cap methylation which is essential to evade immune system.[UniProtKB:P0C6X7] Publication Abstract from PubMedReplication of the approximately 30 kb-long coronavirus genome is mediated by a complex of non-structural proteins (NSP), in which NSP7 and NSP8 play a critical role in regulating the RNA-dependent RNA polymerase (RdRP) activity of NSP12. The assembly of NSP7, NSP8 and NSP12 proteins is highly dynamic in solution, yet the underlying mechanism remains elusive. We report the crystal structure of the complex between NSP7 and NSP8 of SARS-CoV-2, revealing a 2:2 heterotetrameric form. Formation of the NSP7-NSP8 complex is mediated by two distinct oligomer interfaces, with interface I responsible for heterodimeric NSP7-NSP8 assembly, and interface II mediating the heterotetrameric interaction between the two NSP7-NSP8 dimers. Structure-guided mutagenesis, combined with biochemical and enzymatic assays, further reveals a structural coupling between the two oligomer interfaces, as well as the importance of these interfaces for the RdRP activity of the NSP7-NSP8-NSP12 complex. Finally, we identify an NSP7 mutation that differentially affects the stability of the NSP7-NSP8 and NSP7-NSP8-NSP12 complexes leading to a selective impairment of the RdRP activity. Together, this study provides deep insights into the structure and mechanism for the dynamic assembly of NSP7 and NSP8 in regulating the replication of the SARS-CoV-2 genome, with important implications for antiviral drug development. Two conserved oligomer interfaces of NSP7 and NSP8 underpin the dynamic assembly of SARS-CoV-2 RdRP.,Biswal M, Diggs S, Xu D, Khudaverdyan N, Lu J, Fang J, Blaha G, Hai R, Song J Nucleic Acids Res. 2021 Jun 4;49(10):5956-5966. doi: 10.1093/nar/gkab370. PMID:33999154[2] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. See AlsoReferences
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