{"doi":"10.3390/v9100292","title":"Polyprotein Processing as a Determinant for in Vitro Activity of Semliki Forest Virus Replicase","abstract":"<jats:p>Semliki Forest virus (SFV) is an arthropod-borne alphavirus that induces membrane invaginations (spherules) in host cells. These harbor the viral replication complexes (RC) that synthesize viral RNA. Alphaviruses have four replicase or nonstructural proteins (nsPs), nsP1–4, expressed as polyprotein P1234. An early RC, which synthesizes minus-strand RNA, is formed by the polyprotein P123 and the polymerase nsP4. Further proteolytic cleavage results in a late RC consisting of nsP1–4 and synthesizing plus strands. Here, we show that only the late RCs are highly active in RNA synthesis in vitro. Furthermore, we demonstrate that active RCs can be isolated from both virus-infected cells and cells transfected with the wild-type replicase in combination with a plasmid expressing a template RNA. When an uncleavable polyprotein P123 and polymerase nsP4 were expressed together with a template, high levels of minus-strand RNA were produced in cells, but RCs isolated from these cells were hardly active in vitro. Furthermore, we observed that the uncleavable polyprotein P123 and polymerase nsP4, which have previously been shown to form spherules even in the absence of the template, did not replicate an exogenous template. Consequently, we hypothesize that the replicase proteins were sequestered in spherules and were no longer able to recruit a template.</jats:p>","journal":"Viruses","year":2017,"id":16738,"datarank":0.6606076690114641,"base_score":2.639057329615259,"endowment":2.639057329615259,"self_citation_contribution":0.3958585994422889,"citation_network_contribution":0.26474906956917515,"self_endowment_contribution":0.3958585994422889,"citer_contribution":0.26474906956917515,"corpus_percentile":null,"corpus_rank":null,"citation_count":13,"citer_count":10,"citers_with_citation_signal":9,"citers_with_endowment":9,"datacite_reuse_total":0,"is_dataset":false,"is_dataset_confidence":null,"is_data_producer":false,"deposit_databanks":null,"is_oa":false,"file_count":0,"downloads":0,"has_version_chain":false,"published_date":null,"fair_score":null,"fair_percentile":null,"algorithm_id":"datarank_citation_only_1hop_v6","ranking_scope":"data_only","authors":[{"id":122426,"name":"Irina C. Albulescu","orcid":null,"position":1,"is_corresponding":false},{"id":122427,"name":"Martijn J. van Hemert","orcid":null,"position":2,"is_corresponding":false},{"id":122428,"name":"Tero Ahola","orcid":null,"position":3,"is_corresponding":false},{"id":122425,"name":"Maija K. Pietilä","orcid":null,"position":0,"is_corresponding":false}],"reference_count":0,"raw_metadata":{"has_enrichment":true,"base_score":2.5649493574615367,"endowment":2.5649493574615367,"datacite_reuse_total":0,"file_count":0,"downloads":0,"views":0,"has_version_chain":false,"is_dataset":false,"is_oa":false,"pmid":"28991178","pmcid":"PMC5691643","openalex_id":"https://openalex.org/W2760850092","authors":[],"funders":[{"funder_name":"Academy of Finland","grant_id":"274748","title":"Functional reconstitution of membrane rearrangements induced by viral replication"},{"funder_name":"Academy of Finland","grant_id":"265997","title":"Mechanisms in the formation of membrane structures involved in virus replication"},{"funder_name":"Marie Skłodowska-Curie ETN","grant_id":"264286","title":"European Training Network on (+)RNA Virus Replication and Antiviral Drug Development"},{"funder_name":"Netherlands Organisation for Scientific Research","grant_id":"832.14.002","title":"SysVirDrug: Translating Systems Virology data into broad-spectrum antiviral Drugs"}],"total_grants":4,"fwci":1.5006,"citation_percentile":0.84493789,"influential_citations":0,"citation_trend":[{"year":2018,"count":2},{"year":2019,"count":1},{"year":2020,"count":3},{"year":2021,"count":1},{"year":2022,"count":2},{"year":2023,"count":1},{"year":2025,"count":2}],"oa_status":"gold","license":"cc-by","oa_locations":[{"url":"https://www.mdpi.com/1999-4915/9/10/292/pdf?version=1507367421","host_type":"journal"},{"url":"https://www.mdpi.com/1999-4915/9/10/292/pdf?version=1507367421","host_type":"GOLD"},{"url":"https://www.mdpi.com/1999-4915/9/10/292/pdf?version=1507367421","host_type":"publisher"},{"url":"https://www.mdpi.com/1999-4915/9/10/292/pdf","host_type":"publisher"},{"url":"https://doi.org/10.3390/v9100292","host_type":"journal"},{"url":"https://pubmed.ncbi.nlm.nih.gov/28991178","host_type":"repository"},{"url":"http://hdl.handle.net/1887/116569","host_type":"repository"},{"url":"https://doaj.org/article/a8011f77729d4f57ab89b2f20ec3bbe9","host_type":"repository"},{"url":"https://www.ncbi.nlm.nih.gov/pmc/articles/5691643","host_type":"repository"},{"url":"http://hdl.handle.net/10138/231297","host_type":"journal"},{"url":"https://dx.doi.org/10.3390/v9100292","host_type":"repository"},{"url":"https://hdl.handle.net/1887/116569","host_type":"repository"},{"url":"https://europepmc.org/articles/PMC5691643","host_type":"Europe_PMC"},{"url":"https://europepmc.org/articles/PMC5691643?pdf=render","host_type":"Europe_PMC"},{"url":"http://dx.doi.org/10.3390/v9100292","host_type":""}],"fields_of_study":["Mosquito-borne diseases and control","Viral Infections and Vectors","Insect symbiosis and bacterial influences","Biology","Medicine","0301 basic medicine","0303 health sciences","03 medical and health sciences","Animals","Arthropods","Gene Expression Regulation, Viral","Polyproteins","Protein Processing, Post-Translational","RNA, Viral","RNA-Dependent RNA Polymerase","Semliki forest virus","Viral Nonstructural Proteins","Virus Replication"],"mesh_terms":["Animals","Arthropods","Protein Processing, Post-Translational","RNA-Dependent RNA Polymerase","RNA, Viral","Semliki forest virus","Virus Replication","Gene Expression Regulation, Viral","Viral Nonstructural Proteins","Polyproteins"],"keywords":["Semliki Forest virus","RNA-dependent RNA polymerase","Alphavirus","RNA polymerase","RNA","Biology","Virology","Polymerase","In vitro","Togaviridae","Virus","Molecular biology","Biochemistry","Gene","In vitro replication","RNA synthesis","Nonstructural protein","Replication Complex","Gene Expression Regulation, Viral","Viral Nonstructural Proteins","Virus Replication","Microbiology","QR1-502","Article","Animals","RNA, Viral","Plant biology, microbiology, virology","Arthropods","Protein Processing, Post-Translational","Polyproteins"],"sdg_mappings":[{"sdg_number":3,"sdg_label":"3. Good health"},{"sdg_number":0,"sdg_label":"Life in Land"}],"linked_datasets":[],"clinical_trials":[],"software_tools":[],"database_accessions":[],"source":"live","citation_network_status":"fetched"},"created_at":"2026-06-02T14:35:45.428022Z","pmid":null,"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":[]}