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15 recordsLinked to original sources
PubMed2025

Precursor RNA structural patterns at SF3B1 mutation sensitive cryptic 3' splice sites.

SF3B1 is a core component of the spliceosome involved in branch point recognition and 3' splice site selection. The SF3B1 K700E mutation (lysine to glutamic acid) is common in myelodysplastic syndrome and other blood disorders. SF3B1 K700E mutants utilize novel cryptic 3' splice sites; however, the properties distinguishing SF3B1-sensitive splice junctions from other alternatively spliced junctions are unknown. We identify a subset of 192 cryptic 3' splice junctions with significantly altered use in SF3B1 K700E cells, termed SF3B1-sensitive cryptic 3' splice sites, and 2800 cryptic 3' splice sites used in SF3B1 wild-type, termed SF3B1-resistant. We find that SF3B1-sensitive cryptic 3' splice sites are embedded in extended polypyrimidine tracts. Furthermore, canonical splice sites paired to SF3B1-sensitive cryptic 3' splice sites are significantly weaker than canonical 3' splice sites paired to SF3B1-resistant cryptic 3' splice sites. We test whether SF3B1-sensitive splice sites are structurally different from SF3B1-resistant 3' splice sites using chemical probing. We develop experimental RNA structure data for 83 SF3B1-sensitive junctions and 39 SF3B1-resistant junctions. We find that the pattern of structural accessibility at the NAG splicing motif in cryptic and canonical 3' splice sites is similar. However, the magnitude of accessibility differences is less in paired SF3B1-sensitive splice sites than in paired SF3B1-mutant splice sites. Additionally, SF3B1-sensitive splice junctions are more flexible than SF3B1-resistant junctions. Our results suggest that SF3B1-sensitive splice junctions have unique structure and sequence properties, containing poorly differentiated, weak splice sites that lead to altered 3' splice site recognition in the presence of SF3B1 mutation.

RNA Splicing Factors↗
PubMed2026

Oncogenic SF3B1 mutations alter the splicing of mRNA noncoding regions to induce a novel therapeutic vulnerability.

Oncogenic mutations of SF3B1 are common in myeloid cancers, chronic lymphocytic leukemia (CLL), and select solid tumors. Their mechanistic basis for promoting oncogenesis has been investigated in detail, with the stereotyped missplicing of messenger RNA (mRNA) protein coding sequences most intensively studied. These changes, in genes such as MAP3K7, BRD9, and ABCB7, typically lead to loss of function, thus contributing to cancer pathogenesis. Here, we systematically analyzed the impact of mutant SF3B1 on noncoding regions of mRNA transcripts across disease types, in both cell lines and primary patient specimens. This identified numerous novel and highly reproducible splicing alterations in such regions. Studies of a target gene, DCAF16, revealed multiple complex mutation-induced alterations in its 5' and 3' untranslated regions (UTRs). Remarkably, these were mechanistically associated with increased DCAF16 protein levels in SF3B1-mutant cells, representing, to our knowledge, the first time that oncogenic SF3B1 has been found to increase levels of a target protein in a gain-of-function manner. DCAF16 is a substrate recognition adapter for the DDB1/CUL4 E3 ubiquitin ligase complex. Novel protein degrader small molecules that coopt DCAF16 to degrade BRD4 as a neosubstrate demonstrated preferential selectivity for SF3B1-mutant cancers and CLL primary patient specimens due to increased DCAF16 protein levels. In turn, this reveals the therapeutic relevance of mutant SF3B1 dysregulation of transcript UTRs and uncovers a novel strategy for the treatment of these important neoplasms.

Humans↗
PubMed2005

Mammalian polycomb-mediated repression of Hox genes requires the essential spliceosomal protein Sf3b1.

Polycomb group (PcG) proteins are responsible for the stable repression of homeotic (Hox) genes by forming multimeric protein complexes. We show (1) physical interaction between components of the U2 small nuclear ribonucleoprotein particle (U2 snRNP), including Sf3b1 and PcG proteins Zfp144 and Rnf2; and (2) that Sf3b1 heterozygous mice exhibit skeletal transformations concomitant with ectopic Hox expressions. These alterations are enhanced by Zfp144 mutation but repressed by Mll mutation (a trithorax-group gene). Importantly, the levels of Sf3b1 in PcG complexes were decreased in Sf3b1-heterozygous embryos. These findings suggest that Sf3b1-PcG protein interaction is essential for true PcG-mediated repression of Hox genes.

Animals↗
PubMed2001

Molecular cloning, genetic mapping, and expression of the mouse Sf3b1 (SAP155) gene for the U2 snRNP component of spliceosome.

SAP155, a subunit of the U2 snRNP, is essential for prespliceosome assembly and splicing catalysis of the major spliceosome. Moreover, the protein has been identified in the minor (U12-dependent) spliceosome. These facts strongly suggest that SAP155 is shared by two distinct complexes owing to its importance in the removal of any type of intron. Here we have isolated a cDNA encoding the 146-kDa mouse homolog, designated Sf3b1. The amino acid sequence of Sf3b1 is very highly conserved among homologs from Schizosaccharomyces pombe (52.4% identity) to human (99.6%), and the C-terminal 825 residues of these Sf3b1 homologs show even higher identities. This C-terminal region shows significant similarity to the PR65 subunit of protein phosphatase 2A, which is composed of 15 tandem repeats of a 39 amino acid sequence. Mouse genome analyses showed Sf3bh1 to be a single-copy gene mapping to the central part of Chromosome (Chr) 1. Northern blot analysis and whole mount in situ hybridization revealed Sf3b1 to be ubiquitously expressed in a variety of adult tissues and mid-gestation embryos.

Amino Acid Sequence↗
PubMed2003

Generation of a monoclonal antibody against the mouse Sf3b1 (SAP155) gene product for U2 snRNP component of spliceosome.

SAP155 is a subunit of the U2 snRNP, and plays an important role for prespliceosome assembly and splicing catalysis of the major spliceosome. Recently, it was reported that SAP155 was also a subunit of the minor spliceosome. These suggest that SAP155 is essential for the removal of any type of intron. More recently, a homolog of SAP155 cDNA, designated Sf3b1, was isolated from mouse. In this study, we report the generation of a monoclonal antibody (MAb) against murine Sf3b1 protein. This MAb recognizes endogenous Sf3b1 gene product by Western blotting, but less efficiently by immunoprecipitation.

Animals↗
PubMed2006

The protein kinase DYRK1A phosphorylates the splicing factor SF3b1/SAP155 at Thr434, a novel in vivo phosphorylation site.

BACKGROUND: The U2 small nuclear ribonucleoprotein particle (snRNP) component SF3b1/SAP155 is the only spliceosomal protein known to be phosphorylated concomitant with splicing catalysis. DYRK1A is a nuclear protein kinase that has been localized to the splicing factor compartment. Here we describe the identification of DYRK1A as a protein kinase that phosphorylates SF3b1 in vitro and in cultivated cells. RESULTS: Overexpression of DYRK1A caused a markedly increased phosphorylation of SF3b1 in COS-7 cells as assessed by Western blotting with an antibody specific for phosphorylated Thr-Pro dipeptide motifs. Phosphopeptide mapping of metabolically labelled SF3b1 showed that the majority of the in vivo-phosphopeptides corresponded to sites also phosphorylated by DYRK1A in vitro. Phosphorylation with cyclin E/CDK2, a kinase previously reported to phosphorylate SF3b1, generated a completely different pattern of phosphopeptides. By mass spectrometry and mutational analysis of SF3b1, Thr434 was identified as the major phosphorylation site for DYRK1A. Overexpression of DYRK1A or the related kinase, DYRK1B, resulted in an enhanced phosphorylation of Thr434 in endogenous SF3b1 in COS-7 cells. Downregulation of DYRK1A in HEK293 cells or in HepG2 cells by RNA interference reduced the phosphorylation of Thr434 in SF3b1. CONCLUSION: The present data show that the splicing factor SF3b1 is a substrate of the protein kinase DYRK1A and suggest that DYRK1A may be involved in the regulation of pre mRNA-splicing.

Animals↗
PubMed2026

Systems genetics approaches model the heritable architecture of polyendocrine metabolic ovarian syndrome.

Polyendocrine metabolic ovarian syndrome (PMOS), formerly known as polycystic ovary syndrome (PCOS), is the most common endocrine disorder in women and is closely associated with complex diseases such as cardiovascular disease and type 2 diabetes. However, the mechanistic links between PMOS and its comorbidities remain poorly understood. Here, we present an integrative systems genetics platform that leverages genetic diversity in both mice and humans to dissect the drivers of PMOS and its associated complications. This framework uncovered conserved genetic and environmental factors underlying PMOS, identified susceptible cell types and organs, and elucidated mechanisms linking PMOS to subsequent pathologies. For instance, we showed that increased ovarian area contributes to both PMOS susceptibility and ovarian cancer progression, while specific ovary-heart signaling circuits modulate cardiac function with aging. We further identified ovarian SF3B1-mediated alternative splicing as a key mechanistic link between PMOS and metabolic traits. Pharmacologic inhibition of SF3B1 in mice reduced circulating testosterone, insulin, and glucose levels as well as fat mass expansion. Transcriptomics analysis of ovaries from mice and experiments using human cell lines localized these effects to exon skipping events in granulosa cells. Together, this study offers a mechanistic framework for modeling the diversity of PMOS pathologies and uncovers SF3B1-mediated splicing as a link between ovary function and systemic metabolism.

Female↗
PubMed2026

Mutational Landscape and Clonal Dynamics in AML Undergoing PTCy Hematopoietic Cell Transplantation.

To improve risk stratification, we performed targeted NGS at diagnosis in 191 patients with AML undergoing myeloablative allogeneic HCT with PTCy-based prophylaxis. We also investigated clonal evolution using paired diagnostic and relapse samples from 39 individuals. A total of 610 mutations were detected in 184 patients (96%), most commonly in FLT3 (26%), DNMT3A (25%), RUNX1 (24%), and NPM1 (19%). Sixteen unique fusion genes were identified in 35 patients, with KMT2A (43%) and core binding factor rearrangements (23%) being the most frequent. TP53 and WT1 mutations were strongly associated with adverse outcomes, whereas NPM1 retained favorable significance. RUNX1 co-mutations with SF3B1 or NRAS were associated with inferior survival. In an exploratory allelic analysis, multi-hit TP53 alterations, but not single-hit mutations, were associated with distinctly poorer OS, EFS, and relapse risk. Relapse involved mutational shifts in ∼70% of cases, with significant enrichment of WT1 and more modest increases in TP53, KRAS, ASXL1, NF1, and MECOM, while DNMT3A, TET2, and ASXL1 persisted stably. Neither acute nor chronic graft-versus-host disease was associated with molecular remodeling at relapse. Incorporating TP53 and WT1 into risk models, recognizing context-dependent effects of DNMT3A and RUNX1, and applying longitudinal genomic monitoring may help guide personalized strategies to prevent relapse. Extended abstract BACKGROUND Relapse remains the leading cause of treatment failure after allogeneic hematopoietic cell transplantation (HCT) for acute myeloid leukemia (AML), yet the genetic mechanisms underlying post-transplant relapse remain poorly understood, particularly in the era of post-transplant cyclophosphamide (PTCy). Characterizing the mutational landscape at diagnosis and the clonal evolution leading to relapse may improve post-transplant risk stratification and identify opportunities for personalized surveillance and intervention. OBJECTIVES To characterize the diagnostic mutational landscape, evaluate its prognostic significance, and investigate clonal evolution from diagnosis to relapse in AML patients undergoing myeloablative HCT with PTCy-based graft-versus-host disease prophylaxis. STUDY DESIGN We performed targeted next-generation sequencing (NGS) at diagnosis in 191 consecutive AML patients undergoing myeloablative allogeneic HCT with PTCy-based prophylaxis. Paired diagnostic and relapse samples were available for 39 patients to evaluate clonal evolution. RESULTS A total of 610 mutations were detected in 184 patients (96%), most commonly in FLT3 (26%), DNMT3A (25%), RUNX1 (24%), and NPM1 (19%). Sixteen unique fusion genes were identified in 35 patients, with KMT2A (43%) and core binding factor rearrangements (23%) being the most frequent. TP53 and WT1 mutations were strongly associated with adverse outcomes, whereas NPM1 retained favorable significance. RUNX1 co-mutations with SF3B1 or NRAS were associated with inferior survival. In an exploratory allelic analysis, multi-hit TP53 alterations, but not single-hit mutations, were associated with distinctly poorer OS, EFS, and relapse risk. Relapse involved mutational shifts in ∼70% of cases, with significant enrichment of WT1 and more modest increases in TP53, KRAS, ASXL1, NF1, and MECOM, while DNMT3A, TET2, and ASXL1 persisted stably. Neither acute nor chronic graft-versus-host disease was associated with molecular remodeling at relapse. CONCLUSIONS This study provides a comprehensive characterization of the mutational landscape and clonal evolution of AML undergoing contemporary PTCy-based allogeneic HCT. TP53 and WT1 identify patients at particularly high risk of post-transplant relapse, whereas NPM1 retains favorable prognostic significance. The frequent acquisition of new genetic lesions at relapse underscores the dynamic nature of post-transplant clonal evolution and supports longitudinal molecular monitoring together with genomically informed post-transplant surveillance and relapse-prevention strategies.

Clonal Dynamics↗
PubMed2026

Somatic genetic alterations in pituitary neuroendocrine tumors.

The molecular characterization of pituitary neuroendocrine tumors (PitNETs) has progressed pronouncedly in recent years, unraveling the molecular pathways driving initiation and progression of different PitNET types and allowing a better understanding of their biology. The most frequent recurring somatic driver alterations were recognized in corticotroph PitNETs (USP8, USP48, BRAF) and somatotroph PitNETs (GNAS) and, much less frequently, in lactotroph PitNETs (SF3B1). Additional well-characterized somatic driver alterations, including TP53, ATRX, and DAXX, are enriched in aggressive corticotroph tumors. Identification of new molecular markers and delineation of their clinical phenotypes are enabling further subclassification of PitNETs based on tumor molecular profiles, with earlier recognition of more aggressive variants. These molecular markers also provide an opportunity for new targeted therapies. Beyond single-gene alterations, epigenetic modifications, such as DNA methylation, histone modifications, and noncoding RNA dysregulation, are emerging as important contributors to PitNET pathogenesis and potential therapeutic targets. Multi-omics approaches encompassing genomics, transcriptomics, epigenomics, and proteomics are transforming PitNET classification. In this review, we provide a comprehensive, data-driven update on somatic driver alterations, epigenetic alterations, converging signaling pathways, and the related emerging therapeutic targets in PitNETs, integrating pooled analyses from published cohorts.

Humans↗
PubMed2026

Prognostic impact of age and MDS-associated mutations in NPM1-mutated AML.

Nucleophosmin-1 (NPM1) mutations define a major molecular subtype of acute myeloid leukemia (AML) and is generally associated with favorable prognosis. However, the impact of myelodysplastic syndrome-associated mutations (MDSm+) on patient outcomes within this subgroup remains uncertain. We retrospectively analyzed 271 patients with NPM1-mutated AML from 3 independent cohorts (SWOG, Fred Hutch, and Beat AML) to assess the prognostic significance of MDSm+ and its interaction with age. MDSm+ occurred in 17% of patients, most commonly involving SRSF2 and SF3B1. Although MDSm+ was associated with inferior overall survival (OS) compared with MDSm- in European LeukemiaNet (ELN) 2022 favorable-risk patients (hazard ratio [HR], 2.0; P = .008), this effect was largely driven by worse outcomes in older patients (≥65 years) as older ELN2022 favorable-risk patients had poor OS regardless of the presence of MDSm+ compared with younger patients. After stratification of patients by age, there was not a significant difference between MDSm+ and MDSm- in either younger patients (HR, 0.99; P = .98) or older patients (HR, 1.42; P = .33). These findings indicate that MDSm+ in NPM1 + AML is not independently associated with adverse risk after adjusting for age, and highlight the need for age-adjusted AML risk models.

Journal Article↗
PubMed2026

Genome-wide CRISPR screens map synthetic lethal interactions across recurrent cancer driver alterations.

Synthetic lethality (SL) provides a treatment paradigm for targeting cancer with alterations in driver genes that are not conventionally druggable, including tumor suppressor genes. We execute a series of genome-wide CRISPR screens using functionally validated isogenic cell lines and conduct a large-scale SL analysis using data from the cancer dependency map (DepMap). We chart SL interactions across 15 driver alterations: FBXW7, CCNE1, CDK12, ARID1A, KMT2D, DNMT3A, TET2, KEAP1, STK11, IDH1, SF3B1, SRSF2, U2AF1, chromosome 18q loss, and chromosome 13q loss. We show validation of several SL interactions, including ARID1A and the hexosamine biosynthetic pathway aminotransferase GFPT1, STK11 with CAMK protein kinase MARK2, FBXW7 and the CDK1 regulatory kinase PKMYT1, and CCNE1 amplification and the anaphase-promoting complex or cyclosome (APC/C). In summary, this study offers a rich resource of genetic interactions across cancer drivers enabling the discovery of biological insights and drug targets for future therapeutic development.

CP: cancer↗
PubMed2026

Genome-Wide Impact of Human DBR1 Depletion on RNA Processing Networks Reveal a Connection Between Pre-mRNA Splicing, mRNA Surveillance and Stress Granule Dynamics.

The RNA lariat debranching enzyme DBR1 is essential for intron turnover and RNA metabolism, yet its broader impact on transcriptome regulation remains incompletely defined. To elucidate the consequences of DBR1 depletion, we performed transcriptome-wide RNA sequencing of DBR1-knockdown and wild-type HEK293 cells. Differential expression analysis revealed widespread perturbations in pathways linked to RNA splicing, mRNA surveillance, translational control, and stress-granule biology. Many of the most significantly altered transcripts encode splicing factors and RNA quality-control components, underscoring DBR1's influence on post-transcriptional regulation. Alternative splicing analysis showed changes across multiple event types, with exon skipping accounting for >50% of events, followed by mutually exclusive exons, alternative 5' and 3' splice sites, and retained introns, indicating that DBR1 depletion induces pervasive splicing defects. Direct spliceosome inhibition using isoginkgetin (blocks tri-snRNP recruitment) and pladienolide B (targets SF3B1) reproduced the DBR1-KD mis-splicing patterns of cell signaling genes and factors involved in RNA metabolism, supporting a functional link between DBR1 activity and alternative splicing. Notably, DBR1 knockdown revealed a subset of transcripts that are both NMD-sensitive and enriched within stress granules. Consistent with this observation, G3BP1 immunopurification and confocal microscopy further support a role for DBR1 and UPF1 in stress-granule dynamics, suggesting that these factors may participate at distinct stages to influence mRNA fate under stress conditions. Together, these findings indicate that DBR1 functions beyond lariat RNA turnover as a common regulator of RNA processing, transcriptome stability, and stress granule homeostasis, revealing intricate crosstalk between RNA splicing and RNA quality control pathways in human cells.

Humans↗
PubMed2005

In vivo transcriptional profile analysis reveals RNA splicing and chromatin remodeling as prominent processes for adult neurogenesis.

Neural stem cells and neurogenesis persist in the adult mammalian brain subventricular zone (SVZ). Cells born in the rodent SVZ migrate to the olfactory bulb (Ob) where they differentiate into interneurons. To determine the gene expression and functional profile of SVZ neurogenesis, we performed three complementary sets of transcriptional analysis experiments using Affymetrix GeneChips: (1) comparison of adult mouse SVZ and Ob gene expression profiles with those of the striatum, cerebral cortex, and hippocampus; (2) profiling of SVZ stem cells and ependyma isolated by fluorescent-activated cell sorting (FACS); and (3) analysis of gene expression changes during in vivo SVZ regeneration after anti-mitotic treatment. Gene Ontology (GO) analysis of data from these three separate approaches showed that in adult SVZ neurogenesis, RNA splicing and chromatin remodeling are biological processes as statistically significant as cell proliferation, transcription, and neurogenesis. In non-neurogenic brain regions, RNA splicing and chromatin remodeling were not prominent processes. Fourteen mRNA splicing factors including Sf3b1, Sfrs2, Lsm4, and Khdrbs1/Sam68 were detected along with 9 chromatin remodeling genes including Mll, Bmi1, Smarcad1, Baf53a, and Hat1. We validated the transcriptional profile data with Northern blot analysis and in situ hybridization. The data greatly expand the catalogue of cell cycle components, transcription factors, and migration genes for adult SVZ neurogenesis and reveal RNA splicing and chromatin remodeling as prominent biological processes for these germinal cells.

Animals↗
PubMed2003

Mapping of porcine ESTs obtained from the anterior pituitary.

We report the physical mapping of porcine expressed sequence tags (ESTs) from anterior pituitary clones isolated by differential display PCR in a study using lines selected for reproduction. These ESTs were mapped using a somatic cell hybrid panel (SCHP) and a radiation hybrid panel (IMpRH) as follows (SCHP position, nearest marker on the RH map): SPARCL1 (8q23-q27, SSP1); ATF4 (5p11-p15, AC02); MEF2C [2(1/2q21)-(1/2q22), SW2134]; FTH1 (2p14-p17, SWR783); FRAP1 (6q22-q23, SW1355); PBP (14, SW2508); LOC92004 [13q23-(1/2q41), CP]; and PGRMC1 [Xq22, SW1943]. All RH assignments were at LOD score >6.0 except for PGRMC1 at LOD score 5.4. ESTs TCP1 [12p11-(2/3p13)], SF3B1 (15q23-q26) and Clock (8q11-q12) were assigned using only the SCHP. The map position of SPARCL1 coincides with a quantitative trait loci (QTL) for age at puberty found in the University of Nebraska selection lines. Physical mapping of ESTs reported in the present study contributes to characterization of the transcriptome of anterior pituitary of pigs, adds new information to the public database of the porcine genome expression map, and further develops the porcine-human comparative map.

Animals↗
PubMed2004

Origins of recently gained introns in Caenorhabditis.

The genomes of the nematodes Caenorhabditis elegans and Caenorhabditis briggsae both contain approximately 100,000 introns, of which >6,000 are unique to one or the other species. To study the origins of new introns, we used a conservative method involving phylogenetic comparisons to animal orthologs and nematode paralogs to identify cases where an intron content difference between C. elegans and C. briggsae was caused by intron insertion rather than deletion. We identified 81 recently gained introns in C. elegans and 41 in C. briggsae. Novel introns have a stronger exon splice site consensus sequence than the general population of introns and show the same preference for phase 0 sites in codons over phases 1 and 2. More of the novel introns are inserted in genes that are expressed in the C. elegans germ line than expected by chance. Thirteen of the 122 gained introns are in genes whose protein products function in premRNA processing, including three gains in the gene for spliceosomal protein SF3B1 and two in the nonsense-mediated decay gene smg-2. Twenty-eight novel introns have significant DNA sequence identity to other introns, including three that are similar to other introns in the same gene. All of these similarities involve minisatellites or palindromes in the intron sequences. Our results suggest that at least some of the intron gains were caused by reverse splicing of a preexisting intron.

Amino Acid Sequence↗