title: Reduced fidelity of branch point recognition and alternative splicing induced by the anti-tumor drug spliceostatin A.
abstract: Spliceostatin A (SSA) is a stabilized derivative of a Pseudomonas bacterial fermentation product that displays potent anti-proliferative and anti-tumor activities in cancer cells and animal models. The drug inhibits pre-mRNA splicing in vitro and in vivo and binds SF3b, a protein subcomplex of U2 small nuclear ribonucleoprotein (snRNP), which is essential for recognition of the pre-mRNA branch point. We report that SSA prevents interaction of an SF3b 155-kDa subunit with the pre-mRNA, concomitant with nonproductive recruitment of U2 snRNP to sequences 5' of the branch point. Differences in base-pairing potential with U2 snRNA in this region lead to different sensitivity of 3' splice sites to SSA, and to SSA-induced changes in alternative splicing. Indeed, rather than general splicing inhibition, splicing-sensitive microarray analyses reveal specific alternative splicing changes induced by the drug that significantly overlap with those induced by knockdown of SF3b 155. These changes lead to down-regulation of genes important for cell division, including cyclin A2 and Aurora A kinase, thus providing an explanation for the anti-proliferative effects of SSA. Our results reveal a mechanism that prevents nonproductive base-pairing interactions in the spliceosome, and highlight the regulatory and cancer therapeutic potential of perturbing the fidelity of splice site recognition.
authors.affiliation: Centre de Regulació Genòmica, 08003 Barcelona, Spain.
authors.forename: Anna
authors.initials: A
authors.lastname: Corrionero
authors.forename: Belén
authors.initials: B
authors.lastname: Miñana
authors.forename: Juan
authors.initials: J
authors.lastname: Valcárcel
mesh_terms: D017398:Alternative Splicing / Q000187:drug effects*; D000970:Antineoplastic Agents / Q000494:pharmacology*; D002455:Cell Division / Q000187:drug effects; D015536:Down-Regulation / Q000187:drug effects; D006367:HeLa Cells; D006801:Humans; D010750:Phosphoproteins / Q000378:metabolism; D011485:Protein Binding / Q000187:drug effects; D055550:Protein Stability / Q000187:drug effects; D011714:Pyrans / Q000494:pharmacology*; D012322:RNA Precursors / Q000378:metabolism; D022821:RNA Splice Sites / Q000187:drug effects; D000072260:RNA Splicing Factors; D017413:Ribonucleoprotein, U2 Small Nuclear / Q000378:metabolism; D013141:Spiro Compounds / Q000494:pharmacology*; D017381:Spliceosomes / Q000187:drug effects
chemical_list: D000970:Antineoplastic Agents; D010750:Phosphoproteins; D011714:Pyrans; D012322:RNA Precursors; D022821:RNA Splice Sites; D000072260:RNA Splicing Factors; D017413:Ribonucleoprotein, U2 Small Nuclear; C112491:SF3B1 protein, human; D013141:Spiro Compounds; C553684:spliceostatin A