{"doi":"10.1101/2024.09.05.611469","title":"SARS-CoV-2 Nsp15 antagonizes the cGAS-STING-mediated antiviral innate immune responses","abstract":"Abstract Coronavirus (CoV) Nsp15 is a viral endoribonuclease (EndoU) with a preference for uridine residues. CoV Nsp15 is an innate immune antagonist which prevents dsRNA sensor recognition and stress granule formation by targeting viral and host RNAs. SARS-CoV-2 restricts and delays the host antiviral innate immune responses through multiple viral proteins, but the role of SARS-CoV-2 Nsp15 in innate immune evasion is not completely understood. Here, we generate an EndoU activity knockout rSARS-CoV-2 Nsp15-H234A to elucidate the biological functions of Nsp15. Relative to wild-type rSARS-CoV-2, replication of rSARS-CoV-2 Nsp15-H234A was significantly decreased in IFN-responsive A549-ACE2 cells but not in its STAT1 knockout counterpart. Transcriptomic analysis revealed upregulation of innate immune response genes in cells infected with rSARS-CoV-2 Nsp15-H234A relative to wild-type virus, including cGAS-STING, cytosolic DNA sensors activated by both DNA and RNA viruses. Treatment with STING inhibitors H-151 and SN-011 rescued the attenuated phenotype of rSARS-CoV-2 Nsp15-H234A . SARS-CoV-2 Nsp15 inhibited cGAS-STING-mediated IFN-β promoter and NF-κB reporter activity, as well as facilitated the replication of EV-D68 and NDV by diminishing cGAS and STING expression and downstream innate immune responses. Notably, the decline in cGAS and STING was also apparent during SARS-CoV-2 infection. The EndoU activity was essential for SARS-CoV-2 Nsp15-mediated cGAS and STING downregulation, but not all HCoV Nsp15 share the consistent substrate selectivity. In the hamster model, rSARS-CoV-2 Nsp15-H234A replicated to lower titers in the nasal turbinates and lungs and induced higher innate immune responses. Collectively, our findings exhibit that SARS-CoV-2 Nsp15 serves as a host innate immune antagonist by targeting host cGAS and STING. Significance statement Host innate immune system serves as the primary defense against pathogens, including SARS-CoV-2. Co-evolving with the hosts, viruses develop multiple approaches to escape the host surveillance. SARS-CoV-2 silences and dysregulates innate immune responses, and the chaos of antiviral IFN responses highly correlates to COVID-19 disease severity. Nsp15 is a conventional innate immune antagonist across coronaviruses, but the biological impact about SARS-CoV-2 Nsp15 is still unclear. Here, we provide a novel insight that SARS-CoV-2 Nsp15 hampers the expression of innate immune regulator – cGAS and STING via its endoribonuclease activity, then further ameliorates virus replication.","journal":"bioRxiv (Cold Spring Harbor Laboratory)","year":2024,"id":485690,"datarank":0.0,"base_score":0.0,"endowment":0.0,"self_citation_contribution":0.0,"citation_network_contribution":0.0,"self_endowment_contribution":0.0,"citer_contribution":0.0,"corpus_percentile":null,"corpus_rank":null,"citation_count":5,"citer_count":0,"citers_with_citation_signal":0,"citers_with_endowment":0,"datacite_reuse_total":0,"is_dataset":false,"is_dataset_confidence":0.9497,"is_data_producer":false,"deposit_databanks":null,"is_oa":true,"file_count":0,"downloads":0,"has_version_chain":false,"published_date":"2024-01-01","fair_score":null,"fair_percentile":null,"algorithm_id":"datarank_citation_only_1hop_v6","ranking_scope":"data_only","authors":[{"id":95211,"name":"Yao Yu Yeo","orcid":"0000-0002-7604-2296","position":1,"is_corresponding":false},{"id":870604,"name":"Tsoi Ying Lai","orcid":null,"position":2,"is_corresponding":false},{"id":291522,"name":"Chuan-Tien Hung","orcid":"0000-0001-6899-1312","position":3,"is_corresponding":false},{"id":552500,"name":"Shreyas Kowdle","orcid":"0000-0002-7786-3547","position":4,"is_corresponding":false},{"id":552502,"name":"Griffin D. Haas","orcid":"0000-0002-2517-1071","position":5,"is_corresponding":false},{"id":55231,"name":"Sizun Jiang","orcid":"0000-0001-6149-3142","position":6,"is_corresponding":false},{"id":272522,"name":"Weina Sun","orcid":"0000-0002-2435-5047","position":7,"is_corresponding":false},{"id":110494,"name":"Benhur Lee","orcid":"0000-0003-0760-1709","position":8,"is_corresponding":false},{"id":632922,"name":"Hsin-Ping Chiu","orcid":"0000-0002-5010-7338","position":0,"is_corresponding":true}],"reference_count":67,"raw_metadata":null,"created_at":"2026-07-19T02:07:52.536246Z","pmid":"39282446","pmcid":null,"fwci":null,"citation_percentile":null,"influential_citations":0,"oa_status":null,"license":null,"views":0,"total_file_size_bytes":0,"version_count":0,"fair_f":null,"fair_a":null,"fair_i":null,"fair_r":null,"fair_zscore":null,"fair_rationale":null,"fair_model":null,"fair_agent_version":null,"fair_fulltext_source":null,"fair_has_llm":null,"fair_computed_at":null,"clinical_trials":[],"software_tools":[],"db_accessions":[],"linked_datasets":[],"topics":[]}