Hotspot mutations in the spliceosome gene SF3B1 are reported in ∼20% of uveal melanomas.,SF3B1 is involved in 3′-splice site (3′ss) recognition during RNA splicing; however, the molecular mechanisms of its mutation have remained unclear.,Here we show, using RNA-Seq analyses of uveal melanoma, that the SF3B1R625/K666 mutation results in deregulated splicing at a subset of junctions, mostly by the use of alternative 3′ss.,Modelling the differential junctions in SF3B1WT and SF3B1R625/K666 cell lines demonstrates that the deregulated splice pattern strictly depends on SF3B1 status and on the 3’ss-sequence context.,SF3B1WT knockdown or overexpression do not reproduce the SF3B1R625/K666 splice pattern, qualifying SF3B1R625/K666 as change-of-function mutants.,Mutagenesis of predicted branchpoints reveals that the SF3B1R625/K666-promoted splice pattern is a direct result of alternative branchpoint usage.,Altogether, this study provides a better understanding of the mechanisms underlying splicing alterations induced by mutant SF3B1 in cancer, and reveals a role for alternative branchpoints in disease.,Mutations in the splicing factor SF3B1 are found in uveal melanoma.,Here, Alsafadi et al. use RNA-sequencing data from these cancers and experimental models, and show that mutant SF3B1 promotes alternative branchpoints in a specific gene subset and that the mutant protein gains a new function.
Long non-coding RNAs (lncRNAs) have been shown to be implicated in the complex network of cancer including malignant melanoma and play important roles in tumorigenesis and progression.,However, their functions and downstream mechanisms are largely unknown.,This study aimed to investigate whether BRAF-activated non-coding RNA (BANCR), a novel and potential regulator of melanoma cell, participates in the proliferation of malignant melanoma and elucidate the underlying mechanism in this process.,We found that BANCR was abnormally overexpressed in human malignant melanoma cell lines and tissues, and increased with tumor stages by quantitative PCR.,BANCR knockdown induced by shRNA transfection significantly inhibited proliferation of tumor cells and inactivated MAPK pathway, especially by silencing the ERK1/2 and JNK component.,Moreover, combination treatment of BANCR knockdown and suppression ERK1/2 or JNK (induced by specific inhibitors U0126 or SP600125 respectively) produced synergistic inhibitory effects in vitro.,And the inhibitory effects induced by ERK1/2 or JNK could be rescued by BANCR overexpression.,By tumorigenicity assay in BALB/c nude mice, we further found that BANCR knockdown inhibited tumor growth in vivo.,In addition, patients with high expression of BANCR had a lower survival rate.,Taken together, we confirmed the abnormal upregulation of a novel lncRNA, BANCR, in human malignant melanoma.,BANCR was involved in melanoma cell proliferation both in vitro and in vivo.,The linkage between BANCR and MAPK pathway may provide a novel interpretation for the mechanism of proliferation regulation in malignant melanoma.