101. G‐quadruplex‐forming nucleic acids interact with splicing factor 3B subunit 2 and suppress innate immune gene expression
- Author
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Hiroyuki Seimiya, Koji Ueda, Sachiko Okabe, Kyoko Matsumoto, Keiji Okamoto, Risa Fujii, and Kenichi Ohashi
- Subjects
interferon‐stimulated gene ,RNA Splicing ,Oligonucleotides ,Biology ,Ligands ,Models, Biological ,03 medical and health sciences ,Splicing factor ,Transcription (biology) ,Cell Line, Tumor ,Nucleic Acids ,Splicing factor 3b subunit 2 ,Gene expression ,Genetics ,cancer ,Humans ,innate immune gene ,Ubiquitins ,030304 developmental biology ,Regulation of gene expression ,telomere ,0303 health sciences ,Gene knockdown ,Fused-Ring Compounds ,SF3B2 ,virus diseases ,RNA ,Original Articles ,Cell Biology ,Immunity, Innate ,Cell biology ,G‐quadruplex ,G-Quadruplexes ,Gene Ontology ,STAT1 Transcription Factor ,Gene Expression Regulation ,splicing factor ,Gene Knockdown Techniques ,RNA splicing ,Cytokines ,Original Article ,RNA Splicing Factors ,Protein Binding ,Signal Transduction - Abstract
G‐quadruplex (G4), a non‐canonical higher‐order structure formed by guanine‐rich nucleic acid sequences, affects various genetic events in cis, including replication, transcription and translation. Whereas up‐regulation of innate immune/interferon‐stimulated genes (ISGs) is implicated in cancer progression, G4‐forming oligonucleotides that mimic telomeric repeat‐containing RNA suppress ISG induction in three‐dimensional (3D) culture of cancer cells. However, it is unclear how G4 suppresses ISG expression in trans. In this study, we found that G4 binding to splicing factor 3B subunit 2 (SF3B2) down‐regulated STAT1 phosphorylation and ISG expression in 3D‐cultured cancer cells. Liquid chromatography‐tandem mass spectrometry analysis identified SF3B2 as a G4‐binding protein. Either G4‐forming oligonucleotides or SF3B2 knockdown suppressed ISG induction, whereas Phen‐DC3, a G4‐stabilizing compound, reversed the inhibitory effect of G4‐forming oligonucleotides on ISG induction. Phen‐DC3 inhibited SF3B2 binding to G4 in vitro. SF3B2‐mediated ISG induction appeared to occur independently of RNA splicing because SF3B2 knockdown did not affect pre‐mRNA splicing under the experimental conditions, and pharmacological inhibition of splicing by pladienolide B did not repress ISG induction. These observations suggest that G4 disrupts the ability of SF3B2 to induce ISGs in cancer. We propose a new mode for gene regulation, which employs G4 as an inhibitory trans‐element., We demonstrate that a splicing factor SF3B2 mediates interferon‐stimulated gene (ISG) expression in cancer cells. G‐quadruplex‐forming oligonucleotides bind to SF3B2 and suppress ISG up‐regulation. The findings provide a mechanism for the function of G‐quadruplex as a trans‐element of gene regulation.
- Published
- 2021