Project description:U2AF1 is an important component of the spliceosome complex required for pre-mRNA splicing.Mutations in U2AF1 have been described in myeloid neoplasms, with variants causing specific alterations in 3′ splice site recognition. U2AF1 mutations (MT) are typically acquired later in life and associated with rapid rates of progression to MDS and AML. But how mutations affect U2AF1 function has only begun to be examined. Here we used CRISPR/Cas9 to introduce the S34F mutation to U2AF1 in K562 leukemia cells, generating an isogenic model so that splicing alterations can be attributed solely to mutant U2AF1.
Project description:To investigate the effect of the MDS-associated U2AF1-S34F mutation on gene expression and pre-mRNA splicing in mouse neutrophils, we performed RNA-seq on RNA isolated from bone marrow neutrophils expressing either U2AF1-S34F or U2AF1-WT transgenes
Project description:The splicing factor gene, U2AF1, is recurrently mutated in a variety of human cancers, including lung adenocarcinomas. The most frequent U2AF1 mutant, U2AF1 p.Ser34Phe (S34F), induces specific changes in pre-mRNA splicing, but it is unclear how these splicing changes are regulated. We have used genomic editing methods to modify the U2AF1 gene locus in an immortalized human bronchial epithelial cell line (HBEC3kt) and in human lung adenocarcinoma cells with pre-existing U2AF1 alleles, creating a U2AF1 S34F allele in the endogenous locus of HBEC3kts and inactivating U2AF1 S34F alleles in two lung adenocarcinoma cell lines (H441 and HCC78). By comparing global splicing alterations in these isogenic pairs of cell lines, we have identified many splicing alterations that are associated with the U2AF1 S34F mutation. Further, by decreasing the levels of wild-type U2AF1 in the isogenic HBEC3kt cells, we show that the magnitude of mutant-associated splicing is proportional to the ratio of S34F:WT gene products. This observation suggest that wild-type U2AF1 is a negative regulator of splicing alterations induced by U2AF1 S34F.
Project description:Identification of differentially spliced genes by wild type or S34F mutation of U2AF1 Examination of effects on splicing events by overexpressing wipdtype or S34F mutation of two U2AF1 isoforms in A549 cells. All experimental conditions are performed in duplicate.
Project description:Mutations of the splicing factor U2AF1 are frequent in the myeloid malignancy myelodysplastic syndromes (MDS) and in other cancers. Patients with MDS suffer from peripheral blood cytopenias, including anemia, and increasing bone marrow blasts. We investigated the impact of the common U2AF1 S34F mutation on cellular function and mRNA splicing in the main cell lineages affected in MDS. We demonstrated that U2AF1 S34F expression in human hematopoietic progenitors impairs erythroid differentiation, and skews granulomonocytic differentiation towards granulocytes. RNA-sequencing of erythroid and granulomonocytic colonies revealed that U2AF1 S34F induced a higher number of cassette exon splicing events in granulomonocytic than erythroid cells, and altered mRNA splicing of many transcripts (expressed in both cell types) in a lineage-specific manner. The introduction of isoform changes identified in the target genes H2AFY and STRAP into hematopoietic progenitors recapitulated phenotypes associated with U2AF1 S34F expression in erythroid and/or granulomonocytic cells, suggesting a causal link. Importantly, we provided evidence showing that isoform modulation of the U2AF1 S34F target genes H2AFY and STRAP rescues the erythroid differentiation defect in U2AF1 S34F MDS cells, raising the possibility of using splicing modulators therapeutically. These data have critical implications for understanding MDS phenotypic heterogeneity, and for the development of new targeted therapies.
Project description:R-loops and guanine quadruplexes (G4s) are secondary structures of nucleic acids that are ubiquitously present in cells, and are enriched in promoter regions of genes. By employing a bioinformatic approach based on overlap analysis of transcription factor ChIP-seq datasets, we found that many splicing factors, including U2AF1 whose recognition of 3¢ splicing site is crucial for pre-mRNA splicing, exhibit pronounced enrichment at endogenous R-loop- and DNA G4-structure loci in promoter regions of human genes. We revealed that U2AF1 can bind directly to R-loops and DNA G4 structures at low nM binding affinity. Additionally, we showed the ability of U2AF1 to undergo phase separation, which could be stimulated by binding with R-loops, but not duplex DNA, RNA/DNA hybrid, DNA G4, or single-stranded RNA. We also demonstrated that U2AF1 binds to promoter R-loops in human cells, and this binding competes with U2AF1’s interaction with 3¢-splicing site, thereby modulating pre-mRNA splicing. Together, we uncovered a group of candidate proteins that can bind to both R-loops and DNA G4s, revealed the direct and strong interaction of U2AF1 with these nucleic acid structures, and unveiled new functions of this interaction, i.e., promotion of phase separation of U2AF1 and modulation of mRNA splicing. Our work also established, for the first time, a biochemical basis for U2AF1’s occupancy in gene promoters.
Project description:Somatic mutations in the spliceosome have emerged in recent years as oncogenes in human cancer. These mutations are in the factors involved in splice site selection, including a missense mutation (Ser34Phe) in a conserved nucleic acid binding domain of the spicing factor U2AF1. This protein plays a critical role in recognition of the 3'-splice site and assembly of the pre-spliceosomal complex. However, the role that this mutation plays in oncogenesis is still unknown. Here, we have uncovered a non-canonical function of U2AF1. PAR-CLIP and RIP data show that U2AF1 directly binds mature mRNA in the cytoplasm and that binding on or near the start codon results in translational repression. This splicing-independent translational regulatory role of U2AF1 is altered by the S34F mutation, leading to elevated translation of hundreds of mRNA, as revealed by polysome profiling.
Project description:Whole-exome sequencing studies have identified common mutations affecting genes encoding components of the RNA splicing machinery in hematological malignancies. Here, we sought to determine how mutations affecting the 3' splice site recognition factor U2AF1 altered its normal role in RNA splicing. We find that U2AF1 mutations influence the similarity of splicing programs in leukemias, but do not give rise to widespread splicing failure. U2AF1 mutations cause differential splicing of hundreds of genes, affecting biological pathways implicated in myeloid disease such as DNA methylation (DNMT3B), X chromosome inactivation (H2AFY), the DNA damage response (ATR, FANCA), and apoptosis (CASP8). We show that U2AF1 mutations alter the preferred 3' splice site motif in vivo, in cell culture, and in vitro. Mutations affecting the first and second zinc fingers give rise to different alterations in splice site preference and largely distinct downstream splicing programs. These allele-specific effects are consistent with a computationally predicted model of U2AF1 in complex with RNA. Our findings suggest that U2AF1 mutations contribute to pathogenesis by causing quantitative changes in splicing that affect diverse cellular pathways, and give insight into the normal function of U2AF1’s zinc finger domains. mRNA profiles of K562 cells expressing U2AF1 WT, mutants and knockdown of U2AF1 generated by deep sequencing.
Project description:Mutations in spliceosome genes occur in the bone marrow of approximately 50% of patients with myelodysplastic syndromes (MDS), with mutations in the splicing factor gene U2AF1 found in ~11% of MDS patients. We hypothesized that cells harboring a spliceosome gene mutation would have increased sensitivity to further perturbation of the spliceosome by splicing modulator drugs. To examine the effects of the splicing modulator drug sudemycin D6 on primary hematopoietic cells expressing mutant U2AF1(S34F), we treated transgenic mice expressing either mutant U2AF1(S34F) or U2AF1(wildtype, WT) concurrently with 5 days of sudemycin D6 treatment in vivo. We harvested bulk bone marrow cells 18 hours after the last day of treatment and performed strand-specific transcriptome sequencing to examine the cumulative pre-mRNA splicing changes associated with both mutant U2AF1 expression and sudemycin D6 treatment.