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Updated: Jan 7, 2026

A Reporter Based Cellular Assay for Monitoring Splicing Efficiency
Published on: September 15, 2021
SF3B1K700E rewires splicing of cell cycle regulators
Mai Baker1,2, Eden Engel3,4, Aveksha Sharma3
1Department of Biochemistry and Molecular Biology, The Institute for Medical Research Israel-Canada, Faculty of Medicine, The Hebrew University of Jerusalem, Jerusalem 9112102, Israel mib.sal89@gmail.com maayan.salton@mail.huji.ac.il.
Abstract:
Pre-mRNA splicing plays a crucial role in maintaining cellular homeostasis, with strict regulation required for processes such as cell cycle progression. SF3B1, a core component of the spliceosome, has emerged as a key player in alternative splicing regulation and is frequently mutated in cancer. Among these mutations, SF3B1K700E disrupts normal splicing patterns and deregulates cell cycle control. Here we profiled K562 erythroleukemia cells expressing either wild type or SF3B1K700E by RNA-seq and uncovered 763 high-confidence splicing alterations enriched for G2/M regulators, including ARPP19, ENSA, STAG2, and ECT2. Notably, increased inclusion of ARPP19 exon 2 produces the ARPP19-long isoform, which sustains PP2A-B55 inhibition and promotes mitotic progression. A core subset of the K700E-linked splicing changes reappeared after siRNA-mediated SF3B1 depletion in HeLa cells, underscoring a mutation-dependent spliceosomal signature that transcends cell type. Pharmacological inhibition of DYRK1A or broad serine/threonine phosphatases shifted ARPP19 exon 2 inclusion in the same direction as SF3B1K700E, pointing to a kinase-phosphatase signaling axis that influences these splice events. Functionally, ectopic expression of ARPP19-long accelerated mitotic exit, and high ARPP19-long abundance is associated with poorer overall survival in the TCGA-AML cohort. Our findings highlight a connection between SF3B1-dependent splicing, cell cycle progression, and tumorigenesis, offering new insights into the molecular mechanisms underlying cancer-associated splicing dysregulation.
Insights
Mutations in SF3B1 (a spliceosome component) disrupt RNA splicing, affecting cell cycle control and promoting cancer. The SF3B1K700E mutation specifically alters splicing of G2/M regulators like ARPP19, impacting cell division and patient survival.
Area of Science:
- Molecular Biology
- Cancer Biology
- Genetics
Background:
- Pre-mRNA splicing is vital for cellular homeostasis and tightly regulated, especially for cell cycle progression.
- SF3B1, a spliceosome component, is crucial for alternative splicing and frequently mutated in cancers.
- The SF3B1K700E mutation disrupts splicing and cell cycle control, contributing to tumorigenesis.
Purpose of the Study:
- To investigate the impact of SF3B1K700E mutation on RNA splicing patterns.
- To identify splicing alterations linked to the SF3B1K700E mutation and their functional consequences.
- To explore the relationship between SF3B1-dependent splicing, cell cycle regulation, and cancer development.
Main Methods:
- RNA sequencing (RNA-seq) of K562 erythroleukaemia cells expressing wild-type or SF3B1K700E.
- siRNA-mediated depletion of SF3B1 in HeLa cells to validate mutation-dependent splicing signatures.
- Pharmacological inhibition of DYRK1A and serine/threonine phosphatases.
- Functional assays including ectopic expression of ARPP19-long isoform.
- Analysis of TCGA-AML cohort data.
Main Results:
- Identified 763 high-confidence splicing alterations in SF3B1K700E cells, enriched for G2/M regulators (e.g., ARPP19, ENSA, STAG2, ECT2).
- Increased inclusion of ARPP19 exon 2 leads to ARPP19-long isoform, inhibiting PP2A-B55 and promoting mitosis.
- A subset of SF3B1K700E-linked splicing changes were observed upon SF3B1 depletion, indicating a mutation-specific spliceosomal signature.
- Kinase-phosphatase signaling (DYRK1A, phosphatases) influences ARPP19 exon 2 inclusion.
- Ectopic ARPP19-long expression accelerated mitotic exit; high ARPP19-long levels correlated with poorer survival in AML patients.
Conclusions:
- SF3B1K700E mutation drives specific splicing alterations impacting cell cycle regulators.
- The ARPP19-long isoform plays a role in mitotic progression and is linked to adverse outcomes in AML.
- SF3B1-dependent splicing dysregulation is a key mechanism in cancer development, offering potential therapeutic targets.
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