This is highly crucial as a report by Seiler et al. recent clinical trials. Here we review Cenerimod the role of alternative splicing in disease, approaches to rescue incorrect splicing using engineered splicing factors, and small molecule splicing inhibitors developed to treat hematological cancers. Graphical_Abstract Introduction Alternative splicing (AS) of precursor messenger RNA Rabbit Polyclonal to SSTR1 is responsible for the precise regulation of gene expression and AS dysregulation is the cause of various human genetic diseases . The final spliced fate of an RNA transcript depends on which potential splice sites in a transcript are chosen by the spliceosome, a megadalton ribonucleoprotein complex . Aberrant splicing can occur when 1) mutations arise in the splicing signals of a gene or 2) mutations arise in the spliceosomal genes themselves. A splicing signal mutation can prevent proper association of the spliceosome at an intron/exon boundary or activate usage of a cryptic splice site in another location of the gene . Mutations in splicing factor genes change alternative splicing patterns by altering the binding affinities of the splicing factor proteins for their targets in the RNA . These two mechanisms lead to human disease. In this review, we will address therapeutic strategies utilized against both of these mutation modes of AS. AS also contributes to mechanisms of cancer resistance by modulating drug targets, which is well reviewed by Siegfried and Karni  and not further discussed here. Spliceosomes dynamically assemble across introns and exons The excision of introns and ligation of exons to process a pre-mRNA into a protein-coding transcript is completed by a multitude of transcript, allowing production of full length mRNA . To restore correct splicing of a gene causing retinitis pigmentosa, researchers transfected mutant U1 snRNAs into patient-derived primary skin fibroblasts and demonstrated improved splicing of the target transcript [22,23]. Another study focused on another engineered splicing protein, U2AF, to promote the wild-type splicing isoform . These engineered U1 snRNAs have also been studied as HIV-1 inhibitors. Targeting the U1 snRNP to the 3′ end of HIV-1 mRNA substantially reduced viral protein expression in cell lines by blocking pre-mRNA polyadenylation and targeting the HIV-1 mRNA for degradation . These studies highlight the wide variety of diseases that can potentially be treated using this approach, but also show that current research has been primarily focused on using U1 snRNA as a splicing modulator in cell lines or mice expressing human minigenes. In addition to engineering splicing factor genes, small molecules have been identified that can stabilize the spliceosome on mutated splicing signals. A small molecule stabilizer of Cenerimod pre-mRNA and the U1 snRNP complex elevates levels of full-length SMN protein and extends the survival of SMA mice  (Figure 2C). These small molecule therapies have been proven to increase motor function and longevity in these mice models . Despite the low toxicities and therapeutic successes observed in mouse studies, there have not been any clinical trials attempted yet using this engineered splicing factor approach. Further studies will be needed to determine the specificity of this technology and any potential off-target effects before application to human patients. Common splicing factor mutations that lead to cancer Mutations in the spliceosome drive many cancers , as a disease-relevant mutation in a spliceosomal gene induces widespread changes to intron/exon recognition in the cell. Given the relationship between spliceosome mutations and cancer progression, the spliceosome also represents a therapeutic vulnerability . As there are a limiting number of spliceosomes in the cell, spliceosome substrate competition will have strong global splicing affects [30,31]. Cancers with spliceosome mutations depend on wild-type spliceosome functionality for survival [32,33?]. High-throughput sequencing experiments have implicated four splicing factor mutations in various cancers. These mutations alter splicing factor functionality with far-reaching Cenerimod impacts on downstream genes and pathways that enable cancerous growth. Change/gain-of-function mutations in the genes for splicing factor 3B subunit 1 (SF3B1) , U2 small nuclear RNA auxiliary factor 1 (U2AF1) [35,36], and serine/arginine rich splicing factor 2 Cenerimod (SRSF2) [4,37] are frequent in patients with myelodysplastic syndromes (MDS) , chronic myelomonocytic leukemia (CMML), and chronic lymphocytic leukemia (CLL).