Soret Johann, Gabut Mathieu, Dupon Cecile, Kohlhagen Glenda, Stévenin James, Pommier Yves, Tazi Jamal
Institut de Génétique Moléculaire, Centre National de la Recherche Scientifique/UMR5535, and Institut Fédératif de Recherches 122 Montpellier, France.
Cancer Res. 2003 Dec 1;63(23):8203-11.
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.
DNA拓扑异构酶I（Topo I）特异性地使富含精氨酸 - 丝氨酸（SR蛋白）的剪接因子磷酸化，并可能参与前体mRNA剪接调控。我们使用一个因对高剂量抗肿瘤药物喜树碱具有抗性而筛选出的Topo I缺陷型小鼠B淋巴瘤衍生亚克隆（P388 - 45/C），发现Topo I缺失导致SR蛋白的磷酸化不足，并损害外显子剪接增强子（ESE）依赖的剪接，但不影响组成型剪接。Affymetrix基因芯片系统分析显示，几个以小外显子和大内元为特征的可变剪接基因在Topo I缺陷细胞中表达下调。鉴于在Topo I缺陷细胞中绿色荧光蛋白 - Topo I融合蛋白的异位表达可恢复SR蛋白的野生型磷酸化和ESE依赖的剪接，我们得出结论，Topo I介导的磷酸化在ESE调控的剪接中起特定作用。
