title: An siRNA Screen Identifies the U2 snRNP Spliceosome as a Host Restriction Factor for Recombinant Adeno-associated Viruses.
abstract: Adeno-associated viruses (AAV) have evolved to exploit the dynamic reorganization of host cell machinery during co-infection by adenoviruses and other helper viruses. In the absence of helper viruses, host factors such as the proteasome and DNA damage response machinery have been shown to effectively inhibit AAV transduction by restricting processes ranging from nuclear entry to second-strand DNA synthesis. To identify host factors that might affect other key steps in AAV infection, we screened an siRNA library that revealed several candidate genes including the PHD finger-like domain protein 5A (PHF5A), a U2 snRNP-associated protein. Disruption of PHF5A expression selectively enhanced transgene expression from AAV by increasing transcript levels and appears to influence a step after second-strand synthesis in a serotype and cell type-independent manner. Genetic disruption of U2 snRNP and associated proteins, such as SF3B1 and U2AF1, also increased expression from AAV vector, suggesting the critical role of U2 snRNP spliceosome complex in this host-mediated restriction. Notably, adenoviral co-infection and U2 snRNP inhibition appeared to target a common pathway in increasing expression from AAV vectors. Moreover, pharmacological inhibition of U2 snRNP by meayamycin B, a potent SF3B1 inhibitor, substantially enhanced AAV vector transduction of clinically relevant cell types. Further analysis suggested that U2 snRNP proteins suppress AAV vector transgene expression through direct recognition of intact AAV capsids. In summary, we identify U2 snRNP and associated splicing factors, which are known to be affected during adenoviral infection, as novel host restriction factors that effectively limit AAV transgene expression. Concurrently, we postulate that pharmacological/genetic manipulation of components of the spliceosomal machinery might enable more effective gene transfer modalities with recombinant AAV vectors.
authors.affiliation: Department of Molecular Medicine, Mayo Clinic, Rochester, Minnesota, United States of America.
authors.forename: Claire A
authors.initials: CA
authors.lastname: Schreiber
authors.affiliation: Department of Molecular Medicine, Mayo Clinic, Rochester, Minnesota, United States of America.
authors.forename: Toshie
authors.initials: T
authors.lastname: Sakuma
authors.affiliation: Department of Dermatology, UC Davis School of Medicine, Sacramento, California, United States of America.
authors.forename: Yoshihiro
authors.initials: Y
authors.lastname: Izumiya
authors.affiliation: Department of Molecular Medicine, Mayo Clinic, Rochester, Minnesota, United States of America.
authors.forename: Sara J
authors.initials: SJ
authors.lastname: Holditch
authors.affiliation: Department of Molecular Medicine, Mayo Clinic, Rochester, Minnesota, United States of America.
authors.forename: Raymond D
authors.initials: RD
authors.lastname: Hickey
authors.affiliation: Department of Chemistry, University of Pittsburgh, Pittsburgh, Pennsylvania, United States of America.
authors.forename: Robert K
authors.initials: RK
authors.lastname: Bressin
authors.affiliation: Department of Chemistry, University of Pittsburgh, Pittsburgh, Pennsylvania, United States of America.
authors.forename: Upamanyu
authors.initials: U
authors.lastname: Basu
authors.affiliation: Department of Chemistry, University of Pittsburgh, Pittsburgh, Pennsylvania, United States of America.
authors.forename: Kazunori
authors.initials: K
authors.lastname: Koide
authors.affiliation: Gene Therapy Center and Department of Genetics, University of North Carolina School of Medicine, Chapel Hill, North Carolina, United States of America.
authors.forename: Aravind
authors.initials: A
authors.lastname: Asokan
authors.affiliation: Department of Molecular Medicine, Mayo Clinic, Rochester, Minnesota, United States of America.
authors.forename: Yasuhiro
authors.initials: Y
authors.lastname: Ikeda
mesh_terms: D002352:Carrier Proteins / Q000378:metabolism*; D002460:Cell Line; D000229:Dependovirus / Q000235:genetics* / Q000472:pathogenicity; D005822:Genetic Vectors; D015698:Genomic Library; D006790:Host-Parasite Interactions / Q000502:physiology*; D006801:Humans; D015151:Immunoblotting; D047468:Immunoprecipitation; D018613:Microscopy, Confocal; D034741:RNA, Small Interfering; D016601:RNA-Binding Proteins; D020133:Reverse Transcriptase Polymerase Chain Reaction; D017413:Ribonucleoprotein, U2 Small Nuclear / Q000378:metabolism; D017381:Spliceosomes / Q000378:metabolism*; D015534:Trans-Activators; D014161:Transduction, Genetic
chemical_list: D002352:Carrier Proteins; C486761:PHF5A protein, human; D034741:RNA, Small Interfering; D016601:RNA-Binding Proteins; D017413:Ribonucleoprotein, U2 Small Nuclear; D015534:Trans-Activators