title: Altered serine/arginine-rich protein phosphorylation and exonic enhancer-dependent splicing in Mammalian cells lacking topoisomerase I.
abstract: DNA topoisomerase I (Topo I) specifically phosphorylates arginine-serine-rich (SR proteins) splicing factors and is potentially involved in pre-mRNA-splicing regulation. Using a Topo I-deficient murine B lymphoma-derived subclone (P388-45/C) selected for its resistance to high dosage of the antitumor drug camptothecin, we show that Topo I depletion results in the hypophosphorylation of SR proteins and impairs exonic splicing enhancer (ESE)-dependent but not constitutive splicing. The Affymetrix GeneChip system analysis revealed that several alternatively spliced genes, characterized by small exons and large introns, are down-regulated in Topo I-deficient cells. Given that ectopic expression of green fluorescent protein-Topo I fusion in Topo I-deficient cells restores both wild-type phosphorylation of SR proteins and ESE-dependent splicing, we conclude that Topo I-mediated phosphorylation plays a specific role in ESE-regulated splicing.
authors.affiliation: Institut de Génétique Moléculaire, Centre National de la Recherche Scientifique/UMR5535, and Institut Fédératif de Recherches 122 Montpellier, France.
authors.forename: Johann
authors.initials: J
authors.lastname: Soret
authors.forename: Mathieu
authors.initials: M
authors.lastname: Gabut
authors.forename: Cecile
authors.initials: C
authors.lastname: Dupon
authors.forename: Glenda
authors.initials: G
authors.lastname: Kohlhagen
authors.forename: James
authors.initials: J
authors.lastname: Stévenin
authors.forename: Yves
authors.initials: Y
authors.lastname: Pommier
authors.forename: Jamal
authors.initials: J
authors.lastname: Tazi
mesh_terms: D017398:Alternative Splicing; D000818:Animals; D000970:Antineoplastic Agents / Q000494:pharmacology; D002166:Camptothecin / Q000494:pharmacology; D004264:DNA Topoisomerases, Type I / Q000172:deficiency* / Q000235:genetics; D015536:Down-Regulation; D019008:Drug Resistance, Neoplasm; D005091:Exons / Q000502:physiology; D015973:Gene Expression Regulation, Leukemic; D049452:Green Fluorescent Proteins; D007941:Leukemia P388 / Q000201:enzymology / Q000235:genetics; D008164:Luminescent Proteins / Q000096:biosynthesis / Q000235:genetics; D051379:Mice; D009687:Nuclear Proteins / Q000378:metabolism*; D010750:Phosphoproteins / Q000378:metabolism*; D010766:Phosphorylation; D012326:RNA Splicing / Q000502:physiology*; D016601:RNA-Binding Proteins; D011993:Recombinant Fusion Proteins / Q000096:biosynthesis / Q000235:genetics / Q000378:metabolism; D000068103:Serine-Arginine Splicing Factors; D015533:Transcriptional Activation
chemical_list: D000970:Antineoplastic Agents; D008164:Luminescent Proteins; D009687:Nuclear Proteins; D010750:Phosphoproteins; D016601:RNA-Binding Proteins; D011993:Recombinant Fusion Proteins; D049452:Green Fluorescent Proteins; D000068103:Serine-Arginine Splicing Factors; D004264:DNA Topoisomerases, Type I; D002166:Camptothecin