The spliceosome machinery is composed of multimeric protein complexes that generate a diverse repertoire of mRNA through coordinated splicing of heteronuclear RNAs. While somatic mutations in spliceosome components have been discovered in several cancer types, the molecular bases and consequences of spliceosome aberrations in cancer are poorly understood. Here we report for the first time that PRPF6, a member of the tri-snRNP (small ribonucleoprotein) spliceosome complex, drives cancer proliferation by preferential splicing of genes associated with growth regulation. Inhibition of PRPF6 and other tri-snRNP complex proteins, but not other snRNP spliceosome complexes, selectively abrogated growth in cancer cells with high tri-snRNP levels. High-resolution transcriptome analyses revealed that reduced PRPF6 alters the constitutive and alternative splicing of a discrete number of genes, including an oncogenic isoform of the ZAK kinase. These findings implicate an essential role for PRPF6 in cancer via splicing of distinct growth-related gene products.

Abstract Spliceosome coordinated RNA splicing is an essential cellular process that can generate an immensely diverse repertoire of RNA. While cancer cells have been known to hijack this process to generate splice forms with oncogenic function, the specific role of spliceosome components in this process is not well understood. In this study, we use an integrative genomic approach to identify PRPF6, a member of the tri-snRNP spliceosome complex as essential for colon cancer growth. We show that, in addition to PRPF6, other tri-snRNP components are coordinately overexpressed or amplified in cancer cells. Inhibition of the tri-snRNP complex, but not other spliceosome components, abrogated cancer cell growth only in dependent cancer cell lines in vitro and in vivo. High resolution transcriptome analysis reveals that the tri-snRNP complex binds and regulates the splicing of a relatively small number of genes, many of which are transcriptional targets of the c-MYC oncogene. Intriguingly, many components of the tri-snRNP complex are mutated in a genetic form of Retinitis Pigmentosa. This genetic corollary suggests that the tri-snRNP complex is necessary in specific cellular contexts that may depend on the proper transcription and splicing of a tri-snRNP regulated set of genes. Citation Format: Adam Adler, Zhaoshi Jiang, Mark McCleland, Elizabeth Blackwood, Sharon Yee, Benjamin Haley, Jean-Philippe Stephan, Sofia Hussain, Vivek Chopra, Ron Firestein. The tri-snRNP spliceosome complex is required for MYC-dependent cancer growth. [abstract]. In: Proceedings of the 104th Annual Meeting of the American Association for Cancer Research; 2013 Apr 6-10; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2013;73(8 Suppl):Abstract nr 3203. doi:10.1158/1538-7445.AM2013-3203 Note: This abstract was not presented at the AACR Annual Meeting 2013 because the presenter was unable to attend.