{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,8,3]],"date-time":"2026-08-03T11:44:22Z","timestamp":1785757462092,"version":"3.56.0"},"reference-count":44,"publisher":"Wiley","license":[{"start":{"date-parts":[[2026,8,3]],"date-time":"2026-08-03T00:00:00Z","timestamp":1785715200000},"content-version":"vor","delay-in-days":0,"URL":"http:\/\/creativecommons.org\/licenses\/by\/4.0\/"},{"start":{"date-parts":[[2026,8,3]],"date-time":"2026-08-03T00:00:00Z","timestamp":1785715200000},"content-version":"tdm","delay-in-days":0,"URL":"http:\/\/doi.wiley.com\/10.1002\/tdm_license_1.1"}],"funder":[{"DOI":"10.13039\/501100002241","name":"Japan Science and Technology Agency","doi-asserted-by":"publisher","award":["JPMJFR2429"],"award-info":[{"award-number":["JPMJFR2429"]}],"id":[{"id":"10.13039\/501100002241","id-type":"DOI","asserted-by":"publisher"}]},{"DOI":"10.13039\/100007428","name":"Naito Foundation","doi-asserted-by":"publisher","id":[{"id":"10.13039\/100007428","id-type":"DOI","asserted-by":"publisher"}]}],"content-domain":{"domain":["chemistry-europe.onlinelibrary.wiley.com"],"crossmark-restriction":true},"short-container-title":["Chemistry A European J"],"abstract":"<jats:title>ABSTRACT<\/jats:title>\n                  <jats:p>Chemically modified small interfering RNAs (siRNAs) are proving to be highly effective as therapeutic agents, but the extent and positioning of chemical modifications must be carefully tuned because the RNA interference (RNAi) machinery imposes intrinsic constraints on siRNA architecture. Here, using a SARS\u2010CoV\u20102\u2010targeting siRNA as a model, we have systematically investigated the positional and extent\u2010dependent tolerance of 4\u2032\u2010thioRNA substitution within functional siRNAs. Single 4\u2032\u2010thioRNA substitution was broadly tolerated across multiple positions, and complete substitution of either the sense or antisense strand preserved robust RNAi activity. In contrast, full substitution of both strands resulted in a pronounced loss of activity. Physicochemical analysis suggested that this loss arises from interference with cleavage and removal of the sense strand during loading of the RNA\u2010induced silencing complex (RISC). Sense\u2010strand segmentation was therefore applied to fully 4\u2032\u2010thio\u2010modified siRNA to mimic the post\u2010cleavage state during RISC loading. This design partially restored RNAi activity, facilitating the development of fully 4'\u2010thio\u2010modified siRNAs with antiviral activity against SARS\u2010CoV\u20102. Collectively, these findings expand the chemical space available for functional siRNA design.<\/jats:p>","DOI":"10.1002\/chem.71507","type":"journal-article","created":{"date-parts":[[2026,8,3]],"date-time":"2026-08-03T10:47:37Z","timestamp":1785754057000},"update-policy":"https:\/\/doi.org\/10.1002\/crossmark_policy","source":"Crossref","is-referenced-by-count":0,"title":["4\u2032\u2010ThioRNA Substitution and Sense\u2010Strand Segmentation for the Design of Functional Fully Modified siRNAs Targeting SARS\u2010CoV\u20102"],"prefix":"10.1002","author":[{"given":"Yuhei","family":"Nogi","sequence":"first","affiliation":[{"name":"Graduate School of Pharmaceutical Science Tokushima University  Tokushima Tokushima Japan"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-2769-1505","authenticated-orcid":false,"given":"Jun","family":"Tsukimoto","sequence":"additional","affiliation":[{"name":"Graduate School of Pharmaceutical Science Tokushima University  Tokushima Tokushima Japan"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0003-4552-5006","authenticated-orcid":false,"given":"Noriko","family":"Saito\u2010Tarashima","sequence":"additional","affiliation":[{"name":"Graduate School of Pharmaceutical Science Tokushima University  Tokushima Tokushima Japan"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0001-9767-990X","authenticated-orcid":false,"given":"Takaaki","family":"Koma","sequence":"additional","affiliation":[{"name":"Department of Microbiology, Graduate School of Medicine Tokushima University  Tokushima Tokushima Japan"},{"name":"Division of Interdisciplinary Research for Medicine and Photonics, Institute of Post\u2010LED Photonics Tokushima University  Tokushima Tokushima Japan"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Masako","family":"Nomaguchi","sequence":"additional","affiliation":[{"name":"Department of Microbiology, Graduate School of Medicine Tokushima University  Tokushima Tokushima Japan"},{"name":"Division of Interdisciplinary Research for Medicine and Photonics, Institute of Post\u2010LED Photonics Tokushima University  Tokushima Tokushima Japan"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Noriaki","family":"Minakawa","sequence":"additional","affiliation":[{"name":"Graduate School of Pharmaceutical Science Tokushima University  Tokushima Tokushima Japan"}],"role":[{"vocabulary":"crossref","role":"author"}]}],"member":"311","published-online":{"date-parts":[[2026,8,3]]},"reference":[{"key":"e_1_2_9_2_1","doi-asserted-by":"crossref","first-page":"806","DOI":"10.1038\/35888","article-title":"Potent and Specific Genetic Interference by Double\u2010stranded RNA in\u00a0Caenorhabditis elegans","volume":"391","author":"Fire A.","year":"1998","journal-title":"Nature"},{"key":"e_1_2_9_3_1","doi-asserted-by":"crossref","first-page":"494","DOI":"10.1038\/35078107","article-title":"Duplexes of 21\u2010Nucleotide RNAs Mediate RNA Interference in Cultured Mammalian Cells","volume":"411","author":"Elbashir S. M.","year":"2001","journal-title":"Nature"},{"key":"e_1_2_9_4_1","doi-asserted-by":"crossref","first-page":"101","DOI":"10.1038\/s41392-020-0207-x","article-title":"Therapeutic siRNA: State of the Art","volume":"5","author":"Hu B.","year":"2020","journal-title":"Signal Transduction and Targeted Therapy"},{"key":"e_1_2_9_5_1","doi-asserted-by":"crossref","first-page":"10969","DOI":"10.1093\/nar\/gkx818","article-title":"Impact of Enhanced Metabolic Stability on Pharmacokinetics and Pharmacodynamics of GalNAc\u2013siRNA Conjugates","volume":"45","author":"Nair J. K.","year":"2017","journal-title":"Nucleic Acids Research"},{"key":"e_1_2_9_6_1","doi-asserted-by":"crossref","first-page":"708","DOI":"10.1016\/j.ymthe.2017.12.021","article-title":"Advanced siRNA Designs Further Improve In\u00a0Vivo Performance of GalNAc\u2010siRNA Conjugates","volume":"26","author":"Foster D. J.","year":"2018","journal-title":"Molecular Therapy"},{"key":"e_1_2_9_7_1","doi-asserted-by":"crossref","first-page":"2185","DOI":"10.1093\/nar\/gky037","article-title":"Comparison of Partially and Fully Chemically\u2010Modified siRNA in Conjugate\u2010Mediated Delivery In Vivo","volume":"46","author":"Hassler M. R.","year":"2018","journal-title":"Nucleic Acids Research"},{"key":"e_1_2_9_8_1","doi-asserted-by":"crossref","first-page":"11","DOI":"10.1089\/nat.2016.0639","article-title":"Impact of Oligonucleotide Structure, Chemistry, and Delivery Method on In Vitro Cytotoxicity","volume":"27","author":"Janas M. M.","year":"2017","journal-title":"Nucleic Acid Therapeutics"},{"key":"e_1_2_9_9_1","doi-asserted-by":"crossref","first-page":"2705","DOI":"10.1093\/nar\/gkg393","article-title":"Structural Variations and Stabilising Modifications of Synthetic siRNAs in Mammalian Cells","volume":"31","author":"Czauderna F.","year":"2003","journal-title":"Nucleic Acids Research"},{"key":"e_1_2_9_10_1","doi-asserted-by":"crossref","first-page":"4017","DOI":"10.1096\/fj.13-228668","article-title":"Single Modification at Position 14 of siRNA Strand Abolishes Its Gene\u2010Silencing Activity by Decreasing Both RISC Loading and Target Degradation","volume":"27","author":"Zheng J.","year":"2013","journal-title":"FASEB Journal"},{"key":"e_1_2_9_11_1","doi-asserted-by":"crossref","first-page":"644","DOI":"10.1016\/j.ymthe.2006.01.001","article-title":"Progress Towards In Vivo Use of siRNAs","volume":"13","author":"Behlke M. 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K.","year":"2022","journal-title":"Nucleic Acids Research"},{"key":"e_1_2_9_36_1","doi-asserted-by":"crossref","first-page":"5886","DOI":"10.1093\/nar\/gkm548","article-title":"Improved Silencing Properties Using Small Internally Segmented Interfering RNAs","volume":"35","author":"Bramsen J. B.","year":"2007","journal-title":"Nucleic Acids Research"},{"key":"e_1_2_9_37_1","doi-asserted-by":"crossref","first-page":"1805","DOI":"10.1093\/nar\/gkn011","article-title":"Unexpected A\u2010Form Formation of 4\u2032\u2010thioDNA in Solution, Revealed by NMR, and the Implications as to the Mechanism of Nuclease Resistance","volume":"36","author":"Matsugami A.","year":"2008","journal-title":"Nucleic Acids Research"},{"key":"e_1_2_9_38_1","doi-asserted-by":"crossref","DOI":"10.1016\/j.bmc.2022.117093","article-title":"Synthesis and Properties of Fully\u2010Modified 4\u2032\u2010SelenoRNA, an Endonuclease\u2010Resistant RNA Analog","volume":"76","author":"Ota M.","year":"2022","journal-title":"Bioorganic & Medicinal Chemistry"},{"key":"e_1_2_9_39_1","doi-asserted-by":"crossref","first-page":"607","DOI":"10.1016\/j.cell.2005.08.044","article-title":"Passenger\u2010Strand Cleavage Facilitates Assembly of siRNA Into Ago2\u2010Containing RNAi Enzyme Complexes","volume":"123","author":"Matranga C.","year":"2005","journal-title":"Cell"},{"key":"e_1_2_9_40_1","doi-asserted-by":"crossref","first-page":"621","DOI":"10.1016\/j.cell.2005.10.020","article-title":"Argonaute2 Cleaves the Anti\u2010Guide Strand of siRNA During RISC Activation","volume":"123","author":"Rand T. 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