RBFOX2/GOLIM4 Splicing Axis Activates Vesicular Transport Pathway to Promote Nasopharyngeal Carcinogenesis

ABSTRACT 20-30% of patients with nasopharyngeal carcinoma (NPC) develop distant metastasis or recurrence leading to poor survival, of which the underlying key molecular events have yet to be addressed. Here we profiled alternative splicing events in 85 NPC samples using transcriptome analysis and revealed that the long isoform of GOLIM4 (-L) with exon-7 was highly expressed in NPC and associated with poor prognosis. Lines of evidence demonstrated the pro-tumorigenic function of GOLIM4-L in NPC cells. We further revealed that RBFOX2 binds to a GGAA motif in exon-7 and promotes its inclusion forming GOLIM4-L. RBFOX2 knockdown suppressed the tumorigenesis of NPC cells, phenocopying GOLIM4-L knockdown, which was significantly rescued by GOLIM4-L overexpression. Moreover, high expression of RBFOX2 was correlated with the exon-7 inclusion of GOLIM4 in NPC biopsies and associated with worse prognosis. Furthermore, we observed that RBFOX2 and GOLIM4 could influence vesicle-mediated transport through maintaining the organization of Golgi apparatus. Finally, we revealed that RAB26 interacted with GOLIM4 and mediated its tumorigenic potentials in NPC cells. Taken together, our findings provide insights into how alternative splicing contributes to NPC development, by highlighting a functional link between GOLIM4-L and its splicing regulator RBFOX2 activating vesicle-mediated transport involving RAB26. Keywords: GOLIM4, RBFOX2, Nasopharyngeal carcinoma (NPC), Alternative splicing, RAB26 Overall design: We performed transcriptome sequencing of NPC cells to identify RBFOX2 and GOLIM4-L-regulated genes and alternative splicing events.