Selective Translational Control by PABPC1 Phase Separation Regulates Blast Crisis and Therapy Resistance in Chronic Myeloid Leukaemia

Hematology Cell Biology Biochemistry Oncology Life Sciences Medicine
Chronic Myeloid Leukaemia PABPC1 Phase Separation Translational Control Therapy Resistance Blast Crisis CRISPR-Cas9 Screening

Academic Background and Problem Introduction

Chronic Myeloid Leukemia (CML) is a hematologic malignancy driven by the BCR-ABL1 fusion gene. Although Tyrosine Kinase Inhibitors (TKIs) have significantly improved the survival rate of CML patients, TKI resistance and disease progression to the blast crisis (BC) phase remain major challenges in clinical treatment. The prognosis for BC patients is extremely poor, with a median survival of less than one year. Therefore, investigating the molecular mechanisms of CML progression, particularly exploring new therapeutic targets, holds significant clinical importance.

In recent years, increasing evidence suggests that translational control plays a crucial role in cancer progression. However, the specific mechanisms of translational regulation in CML progression remain unclear. This study aims to reveal the translational regulatory mechanisms underlying CML blast crisis through high-throughput screening and functional studies, and to explore potential therapeutic strategies.

Paper Source and Author Information

This study was conducted by a collaborative research team from the Institute of Basic Medical Sciences, Chinese Academy of Medical Sciences, Sun Yat-sen University, Southern Medical University, and other institutions. The corresponding authors are Yanni Ma, Meng Zhao, Jia Yu, and Xiaoshuang Wang. The paper was published in April 2025 in the journal Nature Cell Biology, titled “Selective translational control by PABPC1 phase separation regulates blast crisis and therapy resistance in chronic myeloid leukaemia.”

Research Process and Experimental Design

1. High-Throughput CRISPR-Cas9 Screening

The research team first employed CRISPR-Cas9 screening technology to screen 407 canonical RNA-Binding Proteins (RBPs) in the CML blast crisis cell line K562, aiming to identify key regulatory factors associated with CML progression. The screening results revealed that Poly(A) Binding Protein Cytoplasmic 1 (PABPC1) was significantly upregulated in CML blast crisis and served as a core regulator of protein synthesis and cell proliferation.

2. Functional Validation of PABPC1 in CML Blast Crisis

To validate the function of PABPC1, the research team constructed a conditional knockout mouse model of PABPC1 and conducted in vivo experiments in a BCR-ABL1-induced CML mouse model. The results showed that PABPC1 knockout significantly extended the survival of mice and reduced the infiltration and proliferation of leukemia cells. Additionally, PABPC1 knockout decreased the frequency and activity of Leukemia Stem Cells (LSCs), indicating its critical role in CML blast crisis progression.

3. PABPC1 Selectively Regulates the Translation of Leukemia-Related mRNAs

Through RNA Immunoprecipitation Sequencing (RIP-seq) and Polysome Profiling, the research team found that PABPC1 preferentially binds to and promotes the translation of leukemia-related mRNAs with long and highly structured 5′ Untranslated Regions (5′UTRs), such as BCR-ABL1, IDH2, and HRAS. These genes were significantly upregulated in CML blast crisis, and the reduction in their translation efficiency directly inhibited the proliferation and disease progression of CML cells.

4. Mechanism of PABPC1-Mediated Translational Regulation Through Phase Separation

The research team further discovered that PABPC1 forms biomolecular condensates through Liquid-Liquid Phase Separation (LLPS), thereby recruiting the translation initiation factor eIF4F complex to promote the translation of target mRNAs. The phase separation capability of PABPC1 depends on its Intrinsically Disordered Region (IDR3), and deletion or replacement of IDR3 significantly impairs its translational regulatory function.

5. Screening and Validation of PABPC1 Inhibitors

To explore the therapeutic potential of PABPC1, the research team screened 7,997 compounds using AlphaScreen and identified two small-molecule compounds, 1,10-Phenanthroline and ML324, which effectively inhibit the RNA-binding activity of PABPC1. Both compounds significantly suppressed the proliferation and disease progression of CML cells in vitro and in vivo and were able to overcome TKI resistance.

Main Research Findings

  1. PABPC1 is a Key Regulatory Factor in CML Blast Crisis Progression: High-throughput screening and functional validation demonstrated that PABPC1 is significantly upregulated in CML blast crisis and serves as a core regulator of protein synthesis and cell proliferation.
  2. PABPC1 Selectively Regulates the Translation of Leukemia-Related mRNAs: PABPC1 preferentially binds to and promotes the translation of leukemia-related mRNAs with long and highly structured 5′UTRs, such as BCR-ABL1, IDH2, and HRAS.
  3. PABPC1 Regulates Translation Through Phase Separation: PABPC1 forms biomolecular condensates through LLPS, recruiting the eIF4F complex to promote the translation of target mRNAs.
  4. PABPC1 Inhibitors Have Therapeutic Potential: 1,10-Phenanthroline and ML324 effectively inhibit the RNA-binding activity of PABPC1 and significantly suppress the proliferation and disease progression of CML cells in vitro and in vivo.

Research Conclusions and Significance

This study reveals the critical role of PABPC1 in CML blast crisis progression and elucidates the molecular mechanism by which it selectively regulates the translation of leukemia-related mRNAs through phase separation. Additionally, the research team identified two small-molecule compounds that effectively inhibit PABPC1 function, providing new strategies to overcome TKI resistance and treat CML blast crisis.

Research Highlights

  1. Innovative Discovery: First to reveal the mechanism by which PABPC1 regulates translation through phase separation and identify its critical role in CML blast crisis.
  2. High-Throughput Screening and Functional Validation: Systematically validated the function and mechanism of PABPC1 through CRISPR-Cas9 screening and various functional experiments.
  3. Therapeutic Potential: Identified two small-molecule compounds that effectively inhibit PABPC1 function, providing new drug candidates for CML treatment.

Other Valuable Information

This study also found that PABPC1 is significantly upregulated in TKI-resistant CML cells, and its inhibition can overcome TKI resistance. This discovery offers new perspectives on the mechanisms of TKI resistance and lays the foundation for developing combination therapies.

This research not only deepens our understanding of the molecular mechanisms of CML progression but also provides important theoretical and experimental evidence for developing new therapeutic strategies.