Biology subjects

Krainer, A. R.

Publications and source records attributed to Krainer, A. R..

14 recordsLinked to original sources

bioRxiv2026

The Spliceosome Scaffold Component BCAS2 Promotes Pancreatic Cancer Progression through Weak 5 Splice Site Dependent Splicing Regulation

Pancreatic ductal adenocarcinoma (PDAC) remains one of the deadliest malignancies. Dysregulated RNA splicing has emerged as a critical mechanism contributing to PDAC progression. However, whether structural components of the spliceosome regulate oncogenic alternative splicing was not known. Here, we identify the nineteen complex (NTC) component BCAS2/SPF27 as a critical regulator of PDAC progression. Elevated expression of BCAS2 in PDAC is associated with poor patient outcomes. Transcriptomic analyses revealed that BCAS2 specifically regulates alternative exons with weak splice sites. In particular, BCAS2 promotes SOS1 exon 21 inclusion and consequently RAC-signaling activation. Furthermore, splice-switching antisense oligonucleotide (ASO) mediated skipping of SOS1 exon 21 suppressed PDAC proliferation and migration. Our findings uncover a role of BCAS2 in the regulation of weak splice site usage and identify the BCAS2/SOS1/RAC signaling axis as a potential therapeutic vulnerability in pancreatic cancer.

cancer biology↗

bioRxiv2026

Exon-Skipping Antisense Oligonucleotides for H3.3K27M-Altered Diffuse Midline Glioma Therapy

Diffuse midline gliomas (DMGs) are a deadly class of pediatric high-grade brain cancers. Approximately 80% of pontine DMGs feature a dominant, somatic, heterozygous point mutation in the non-canonical histone H3.3-coding gene H3-3A. This dominant-negative mutation replaces lysine 27 with methionine (K27M) and prevents global K27 di- and tri-methylation of all wild-type histone H3 proteins. We aimed to target the H3.3K27M onco-histone pre-mRNA with splice-switching antisense oligonucleotides (ASOs) designed to promote skipping of H3-3A exon 2, as this constitutive exon comprises both the K27M mutation and the natural in-frame start codon of the gene. The lead ASO identified in a systematic screen specifically induced H3-3A exon 2 skipping, did not affect expression or splicing of the paralog gene H3-3B--which also encodes histone H3.3--and restored global H3K27me3 marks in patient-derived DMG cells grown as neurospheres. In a patient-derived orthotopic xenograft tumor mouse model, the lead ASO reduced proliferation and extended survival. Our results show the potential of exon-skipping ASOs targeting H3-3A exon 2 as a therapeutic option for H3.3K27M-altered DMG. More generally, they exemplify the strategy of using ASOs to induce skipping of a constitutive exon to effectively achieve gene downregulation.

molecular biology↗

bioRxiv2026

Targeting EZH2 Oncogenic Splicing: Decoding the Regulatory Network and Antisense Correction

Recurrent mutations in splicing factors (SFs) have been established as crucial drivers of tumorigenesis in several types of blood cancer, and also common in a variety of solid tumors. Mutations change the RNA-binding preferences of SFs, promote global splicing alterations, and often generate erroneous mRNAs that are then degraded by nonsense-mediated mRNA decay (NMD). Consequently, several critical genes linked to hematopoiesis are dysregulated, leading to blood cancer. Although the field has progressed considerably in identifying aberrant genes and affected pathways, effective therapies have not yet emerged in SF-mutated cancers. To address this key gap, we instigated a gene-specific targeted strategy by unlocking the regulatory network. As a proof-of-concept, we scrutinized a tumor suppressor gene EZH2, which is a bona fide target in SRSF2-mutated cancer. We precisely defined splicing cis-elements in EZH2 transcripts and illustrated the dynamic choreography of regulatory proteins in the entire splicing and NMD catalytic pathways. We uncovered a highly coordinated cross-regulation between splicing and NMD promoted by mutant SRSF2 by enhancing the deposition of critical spliceosome- and NMD-associated factors, augmenting mRNA decay to ablate tumor suppression. We then designed antisense oligonucleotides (ASOs) targeting important regulatory sites. Our lead ASO successfully corrects aberrant splicing and NMD, restores the expression and function of EZH2, and partially rescues hematopoietic defects and cellular properties. Our study demonstrates that ASO pharmacology is an actionable strategy for clinical development, challenging the existing paradigms in SF-mutated cancers.

cancer biology↗

bioRxiv2025

On-target toxicity limits the efficacy of CDK11 inhibition against cancers with 1p36 deletions

The cyclin-dependent kinase CDK11 is an understudied kinase that has been the subject of conflicting reports regarding its function in cancer. Here, we combine genetic and pharmacological approaches to demonstrate that CDK11 is a critical regulator of cancer cell survival that is required for RNA splicing and the expression of homologous recombination genes. Inhibition of CDK11 disrupts genome stability, promotes the retention of intronic sequences in mature mRNAs, and induces synthetic lethality with PARP inhibitors. Through integrative analysis of functional genomics datasets, we identify heterozygous deletions of chromosome 1p36 - which encompasses CDK11 and its activating cyclin CCNL2 - as a recurrent and predictive biomarker of sensitivity to CDK11 inhibition. To assess the therapeutic potential of CDK11, we develop MEL-495R, a selective and orally bioavailable CDK11 inhibitor. Additionally, we establish a genetically-engineered mouse model that allows us to differentiate between the on-target and off-target effects of CDK11 inhibitors in vivo. Using this platform, we demonstrate that MEL-495R induces widespread on-target toxicity, revealing a narrow therapeutic index. Together, these findings define CDK11 as a core cancer dependency, uncover a chromosomal deletion that sensitizes tumors to CDK11 inhibition, and provide a generalizable strategy for deconvolving drug efficacy and toxicity in vivo for novel oncology targets.

cancer biology↗

bioRxiv2025

Splice-switching ASOs targeting an Alu-derived exon in the AURKA 5'UTR collapse an SRSF1-AURKA-MYC oncogenic circuit in pancreatic cancer

Pancreatic ductal adenocarcinoma (PDAC) remains a highly lethal malignancy, driven by oncogenic KRAS mutations and dysregulated oncogenes, such as SRSF1, MYC, and AURKA. Although KRAS-targeted therapies are in development, resistance mechanisms underscore the need to identify alternative vulnerabilities. Here, we uncover an SRSF1-AURKA-MYC oncogenic circuit, wherein SRSF1 regulates AURKA 5UTR alternative splicing, enhancing AURKA protein expression; AURKA positively regulates SRSF1 and MYC post-translationally, independently of its kinase activity; and MYC in turn transcriptionally upregulates both SRSF1 and AURKA. Elevated SRSF1 in tumor cells promotes inclusion of an exonized Alu exon in the AURKA 5UTR, resulting in splicing-dependent mRNA accumulation and exon-junction- complex deposition. Modulating 5UTR splicing with splice-switching antisense oligonucleotides (ASOs) collapses the oncogenic circuit, reducing PDAC cell viability and triggering apoptosis. Our findings identify AURKA alternative splicing as a critical regulatory node and highlight ASO-mediated splice-switching as a potential therapeutic strategy that simultaneously targets SRSF1, AURKA, and MYC oncogenes.

cancer biology↗

bioRxiv2022

Specificity, synergy, and mechanisms of splice-modifying drugs

Drugs that target pre-mRNA splicing hold great therapeutic potential, but the quantitative understanding of how these drugs work is limited. Here we introduce mechanistically interpretable quantitative models for the sequence-specific and concentration-dependent behavior of splice-modifying drugs. Using massively parallel splicing assays, RNA-seq experiments, and precision dose-response curves, we obtain quantitative models for two small-molecule drugs, risdiplam and branaplam, developed for treating spinal muscular atrophy. The results quantitatively characterize the specificities of risdiplam and branaplam for 5 splice site sequences, suggest that branaplam recognizes 5 splice sites via two distinct interaction modes, and disprove the prevailing two-site hypothesis for risdiplam activity at SMN2 exon 7. The results also show that anomalous single-drug cooperativity, as well as multi-drug synergy, are widespread among small-molecule drugs and antisense-oligonucleotide drugs that promote exon inclusion. Our quantitative models thus clarify the mechanisms of existing treatments and provide a basis for the rational development of new therapies.

biophysics↗

bioRxiv2021

Loss of KRASG12D feedback regulation involving splicing factor SRSF1 accelerates pancreatic cancer

The gene encoding KRAS GTPase is recurrently mutated in pancreatic ductal adenocarcinoma (PDAC), triggering the formation of precursor lesions, i.e., acinar-to-ductal metaplasia (ADM) and pancreatic intraepithelial neoplasia (PanIN). However, the majority of pancreatic cells from KC (LSL-KrasG12D/+; Pdx-1-Cre) mice expressing the KrasG12D mutation remain morphologically normal for a long time, suggesting the existence of compensatory feedback mechanisms that buffer aberrant KrasG12D signaling, and that additional steps are required for disrupting cell homeostasis and promoting transformation. Here we report a feedback mechanism in which the ubiquitously expressed splicing factor SRSF1--which is associated with cell transformation in multiple cell types--is downregulated in the majority of morphologically normal pancreas cells with the KrasG12D mutation. Conversely, increasing SRSF1 expression disrupts cell homeostasis by activating MAPK signaling, in part by regulating alternative splicing and mRNA stability of interleukin 1 receptor type 1 (Il1r1). This disruption in homeostasis in turn accelerates KrasG12D-mediated PDAC initiation and progression. Our results demonstrate the involvement of SRSF1 in the pancreatic-cell homeostatic response against the KrasG12D mutation, dysregulation of which facilitates PDAC initiation. One-Sentence SummarySplicing factor SRSF1 is involved in KRASG12D feedback regulation and pancreatic-cancer tumorigenesis.

cancer biology↗

bioRxiv2021

Exon-Skipping Antisense Oligonucleotides for Cystic Fibrosis Therapy

Mutations in the cystic fibrosis transmembrane conductance regulator (CFTR) gene cause cystic fibrosis (CF), and the CFTR-W1282X nonsense mutation causes a severe form of CF. Although Trikafta and other CFTR-modulation therapies benefit most CF patients, targeted therapy for patients with the W1282X mutation is lacking. The CFTR-W1282X protein has residual activity, but is expressed at a very low level due to nonsense-mediated mRNA decay (NMD). NMD-suppression therapy and read-through therapy are actively being researched for CFTR nonsense mutants. NMD suppression could increase the mutant CFTR mRNA, and read-through therapies may increase the levels of full-length CFTR protein. However, these approaches have limitations and potential side effects: because the NMD machinery also regulates the expression of many normal mRNAs, broad inhibition of the pathway is not desirable; and read-through drugs are inefficient, partly because the mutant mRNA template is subject to NMD. To bypass these issues, we pursued an exon-skipping antisense oligonucleotide (ASO) strategy to achieve gene-specific NMD evasion. A cocktail of two splice-site-targeting ASOs induced the expression of CFTR mRNA without the PTC-containing exon 23 (CFTR-{Delta}ex23), which is an in-frame exon. Treatment of human bronchial epithelial cells with this cocktail of ASOs that target the splice sites flanking exon 23 results in efficient skipping of exon 23 and an increase in CFTR-{Delta}ex23 protein. The splice-switching ASO cocktail increases the CFTR-mediated chloride current in human bronchial epithelial cells. Our results set the stage for developing an allele-specific therapy for CF caused by the W1282X mutation.

molecular biology↗

bioRxiv2021

Gene-Specific Nonsense-Mediated mRNA Decay Targeting for Cystic Fibrosis Therapy

Low CFTR mRNA expression due to nonsense-mediated mRNA decay (NMD) is a major hurdle in developing a therapy for cystic fibrosis (CF) caused by the W1282X mutation in the CFTR gene. CFTR-W1282X truncated protein retains partial function, so increasing its levels by inhibiting NMD of its mRNA will likely be beneficial. Because NMD regulates the normal expression of many genes, gene-specific stabilization of CFTR-W1282X mRNA expression is more desirable than general NMD inhibition. Synthetic antisense oligonucleotides (ASOs) designed to prevent binding of exon junction complexes (EJC) downstream of premature termination codons (PTCs) attenuate NMD in a gene-specific manner. We developed a cocktail of three ASOs that specifically increases the expression of CFTR W1282X mRNA and CFTR protein in ASO-transfected human bronchial epithelial cells. This treatment increased the CFTR-mediated chloride current. These results set the stage for clinical development of an allele-specific therapy for CF caused by the W1282X mutation.

molecular biology↗

bioRxiv2020

Empirical variance component regression for sequence-function relationships

Contemporary high-throughput mutagenesis experiments are providing an increasingly detailed view of the complex patterns of genetic interaction that occur between multiple mutations within a single protein or regulatory element. By simultaneously measuring the effects of thousands of combinations of mutations, these experiments have revealed that the genotype-phenotype relationship typically reflects genetic interactions not only between pairs of sites, but also higher-order interactions among larger numbers of sites. However, modeling and understanding these higher-order interactions remains challenging. Here, we present a method for reconstructing sequence-to-function mappings from partially observed data that can accommodate all orders of genetic interaction. The main idea is to make predictions for unobserved genotypes that match the type and extent of epistasis found in the observed data. This information on the type and extent of epistasis can be extracted by considering how phenotypic correlations change as a function of mutational distance, which is equivalent to estimating the fraction of phenotypic variance due to each order of genetic interaction (additive, pairwise, three-way, etc.). Using these estimated variance components, we then define an empirical Bayes prior that in expectation matches the observed pattern of epistasis, and reconstruct the genotype-phenotype mapping by conducting Gaussian process regression under this prior. To demonstrate the power of this approach, we present an application to the antibody-binding domain GB1 and also provide a detailed exploration of a dataset consisting of high-throughput measurements for the splicing efficiency of human pre-mRNA 5' splice sites, for which we also validate our model predictions via additional low-throughput experiments.

evolutionary biology↗

bioRxiv2019

Differential functions of splicing factors in breast-cancer initiation and metastasis

Misregulation of alternative splicing is a hallmark of human tumors; yet to what extent and how it contributes to malignancy are only beginning to be unraveled. Here, we define which members of the splicing factor SR and SR-like families contribute to breast cancer, and uncover differences and redundancies in their targets and biological functions. We first identify splicing factors frequently altered in human breast tumors, and then assay their oncogenic functions using breast organoid models. Importantly we demonstrate that not all splicing factors affect mammary tumorigenesis. Specifically, upregulation of either SRSF4, SRSF6 or TRA2{beta} promotes cell transformation and invasion. By characterizing the targets of theses oncogenic factors, we identify a shared set of spliced genes associated with well-established cancer hallmarks. Finally, we demonstrate that the splicing factor TRA2{beta} is regulated by the MYC oncogene, plays a role in metastasis maintenance in vivo, and its levels correlate with breast-cancer-patient survival.

cancer biology↗

bioRxiv2018

Delivery of GalNAc-conjugated splice-switching ASOs to non-hepatic cells through ectopic expression of asialoglycoprotein receptor

Splice-switching antisense oligonucleotides (ASOs) are promising therapeutic tools to target various genetic diseases, including cancer. However, in vivo delivery of ASOs to orthotopic tumors in cancer mouse models or to certain target tissues remains challenging. A viable solution already in use is receptor-mediated uptake of ASOs via tissue-specific receptors. For example, the asialoglycoprotein receptor (ASGP-R) is exclusively expressed in hepatocytes. Triantennary GalNAc (GN3)-conjugated ASOs bind to the receptor and are efficiently internalized by endocytosis, enhancing ASO potency in the liver. Here we explore the use of GalNAc-mediated targeting to deliver therapeutic splice-switching ASOs to cancer cells that ectopically express ASGP-R, both in vitro and in tumor mouse models. We found that ectopic expression of the major isoform ASGP-R1 H1a is sufficient to promote uptake and increase GN3-ASO potency to various degrees in all tested cancer cells. We show that cell-type specific glycosylation of the receptor does not affect its activity. In vivo, GN3-conjugated ASOs specifically target subcutaneous xenograft tumors that ectopically express ASGP-R1, and modulate splicing significantly more strongly than unconjugated ASOs. Our work shows that GN3-targeting is a useful tool for proof-of-principle studies in orthotopic cancer models, until endogenous receptors are identified and exploited for efficiently targeting cancer cells.

molecular biology↗

bioRxiv2017

A human-specific switch of alternatively spliced AFMID isoforms contributes to TP53 mutations and tumor recurrence in hepatocellular carcinoma

Pre-mRNA splicing can contribute to the switch of cell identity that occurs in carcinogenesis. Here we analyze a large collection of RNA-Seq datasets and report that splicing changes in hepatocyte-specific enzymes, such as AFMID and KHK, are associated with HCC patients survival and relapse. The switch of AFMID isoforms is an early event in HCC development, and is associated with driver mutations in TP53 and ARID1A. Finally, we show that the switch of AFMID isoforms is human-specific and not detectable in other species, including primates. The integrative analysis uncovers a mechanistic link between splicing switches, de novo NAD+ biosynthesis, driver mutations, and HCC recurrence.

bioinformatics↗

bioRxiv2017

De novo indels within introns contribute to ASD incidence

Copy number profiling and whole-exome sequencing has allowed us to make remarkable progress in our understanding of the genetics of autism over the past ten years, but there are major aspects of the genetics that are unresolved. Through whole-genome sequencing, additional types of genetic variants can be observed. These variants are abundant and to know which are functional is challenging. We have analyzed whole-genome sequencing data from 510 of the Simons Simplex Collections quad families and focused our attention on intronic variants. Within the introns of 546 high-quality autism target genes, we identified 63 de novo indels in the affected and only 37 in the unaffected siblings. The difference of 26 events is significantly larger than expected (p-val = 0.01) and using reasonable extrapolation shows that de novo intronic indels can contribute to at least 10% of simplex autism. The significance increases if we restrict to the half of the autism targets that are intolerant to damaging variants in the normal human population, which half we expect to be even more enriched for autism genes. For these 273 targets we observe 43 and 20 events in affected and unaffected siblings, respectively (p-value of 0.005). There was no significant signal in the number of de novo intronic indels in any of the control sets of genes analyzed. We see no signal from de novo substitutions in the introns of target genes.

genetics↗