title: Nuclear cyclophilins affect spliceosome assembly and function in vitro.
abstract: Cyclophilins are ubiquitously expressed proteins that bind to prolines and can catalyse cis/trans isomerization of proline residues. There are 17 annotated members of the cyclophilin family in humans, ubiquitously expressed and localized variously to the cytoplasm, nucleus or mitochondria. Surprisingly, all eight of the nuclear localized cyclophilins are found associated with spliceosomal complexes. However, their particular functions within this context are unknown. We have therefore adapted three established assays for in vitro pre-mRNA splicing to probe the functional roles of nuclear cyclophilins in the context of the human spliceosome. We find that four of the eight spliceosom-associated cyclophilins exert strong effects on splicing in vitro. These effects are dose-dependent and, remarkably, uniquely characteristic of each cyclophilin. Using both qualitative and quantitative means, we show that at least half of the nuclear cyclophilins can act as regulatory factors of spliceosome function in vitro. The present work provides the first quantifiable evidence that nuclear cyclophilins are splicing factors and provides a novel approach for future work into small molecule-based modulation of pre-mRNA splicing.
authors.affiliation: Department of Molecular, Cell and Developmental Biology and Center for Molecular Biology of RNA, University of California, Santa Cruz, CA 95064, U.S.A.
authors.forename: B M
authors.initials: BM
authors.lastname: Adams
authors.affiliation: Department of Molecular, Cell and Developmental Biology and Center for Molecular Biology of RNA, University of California, Santa Cruz, CA 95064, U.S.A.
authors.forename: Miranda N
authors.initials: MN
authors.lastname: Coates
authors.affiliation: Department of Biochemistry and Molecular Biology, Drexel University College of Medicine, Philadelphia, PA 19102, U.S.A.
authors.forename: S RaElle
authors.initials: SR
authors.lastname: Jackson
authors.affiliation: Department of Molecular, Cell and Developmental Biology and Center for Molecular Biology of RNA, University of California, Santa Cruz, CA 95064, U.S.A.
authors.forename: Melissa S
authors.initials: MS
authors.lastname: Jurica
authors.affiliation: Department of Molecular, Cell and Developmental Biology and Center for Molecular Biology of RNA, University of California, Santa Cruz, CA 95064, U.S.A. Department of Biochemistry and Molecular Biology, Drexel University College of Medicine, Philadelphia, PA 19102, U.S.A. Tara.Davis@DrexelMed.edu.
authors.forename: Tara L
authors.initials: TL
authors.lastname: Davis
mesh_terms: D002474:Cell-Free System / Q000737:chemistry / Q000378:metabolism; D021983:Cyclophilins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D006367:HeLa Cells; D006801:Humans; D009687:Nuclear Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D012322:RNA Precursors / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D012326:RNA Splicing / Q000502:physiology*; D017381:Spliceosomes / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*
chemical_list: D009687:Nuclear Proteins; D012322:RNA Precursors; D021983:Cyclophilins
keywords: nuclear cyclophilins; pre-messenger RNA (mRNA) splicing; spliceosome