Altered serine/arginine-rich protein phosphorylation and exonic enhancer-dependent splicing in Mammalian cells lacking topoisomerase I

M. Gabut , C. Dupon , G. Kohlhagen , J. Stevenin (1) , Y. Pommier , J. Tazi (2) , J. Soret (2)

1 IGBMC - Institut de génétique et biologie moléculaire et cellulaire
2 IGMM - Institut de Génétique Moléculaire de Montpellier

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.

Mots clés: Alternative Splicing Animals Antineoplastic Agents/pharmacology Camptothecin/pharmacology DNA Topoisomerases; Leukemic Green Fluorescent Proteins Leukemia P388/enzymology/genetics Luminescent Proteins/biosynthesis/genetics Mice Nuclear Proteins/*metabolism Phosphoproteins/*metabolism Phosphorylation RNA Splicing/*physiology RNA-Binding Proteins Recombinant Fusion Proteins/biosynthesis/genetics/metabolism Trans-Activation (Genetics); Neoplasm Exons/physiology Gene Expression Regulation; Type I/*deficiency/genetics Down-Regulation Drug Resistance

Domaines: Biochimie, Biologie Moléculaire

M. Gabut, C. Dupon, G. Kohlhagen, J. Stevenin, Y. Pommier, et al.. Altered serine/arginine-rich protein phosphorylation and exonic enhancer-dependent splicing in Mammalian cells lacking topoisomerase I. Cancer Research, 2003, 63 (23), pp.8203--11. ⟨hal-02199832⟩