9saq
Cryo-EM structure of SARS CoV-2 RdRp S759A mutant in complex with 20-40mer RNA incorporating ATP
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 PubMedNucleoside analogs (NAs) have been successfully used to treat viral infections. dNTP analogs are primarily DNA chain terminators, while NTP analogs, such as remdesivir, can inhibit as delayed chain terminators or when in the template strand. Determining the frequency of remdesivir triphosphate (RTP) incorporation in the presence of the competing ATP can help in understanding different modes of viral RNA-dependent RNA polymerase (RdRp) inhibition by NTP analogs. We employed enzymatic assays, mass spectrometry, and cryo-EM to show that SARS-CoV-2 RdRp preferentially incorporates RTP, outcompeting 10-fold higher ATP concentration; however, successive RTP incorporations are less favoured when ATP is present. Structures of SARS-CoV-2 RdRp in this and previous studies demonstrate resilience of remdesivir:UMP base pair to translocation, explaining the reduced preference for conjugate incorporations. Together, the RTP versus ATP incorporation is driven by their relative concentration and structural rigidity of remdesivir:UMP, ultimately limiting the number of incorporated remdesivir in a fully synthesized RNA strand. The S759A mutant confers RTP resistance, and the structures of S759A RdRp catalytic complexes reveal that altered ribose-ring conformation and repositioning of the primer 3'-end nucleotide contribute to RTP resistance. These findings enhance our understanding of non-obligate NTP analogs and provide insight into S759A resistance mechanism. Structural basis for selective remdesivir incorporation by SARS-CoV-2 RNA polymerase, and S759A resistance.,Gordon CJ, Oliva MF, Lee HW, Goovaerts Q, De Wijngaert B, Gotte M, Das K bioRxiv [Preprint]. 2025 Sep 4:2025.09.04.674295. doi: 10.1101/2025.09.04.674295. PMID:40950230[2] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. References
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