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CRM1 inhibits NPAT condensation and histone locus body formation via a competitive occupation strategy

Xiao Xia Cong1,2, Shui Bo Xu1,3, Wen Kai Zou1,3

  • 1Department of General Intensive Care Unit and Department of Biochemistry, The Second Affiliated Hospital, Liangzhu Laboratory, Zhejiang University School of Medicine, Hangzhou, China.

The Journal of Cell Biology
|January 2, 2026
PubMed

Insights

Exportin CRM1 binds to nuclear protein NPAT, inhibiting its condensation and histone locus body formation. This competitive occupation mechanism reveals a novel exportin regulatory strategy for nuclear protein condensation.

Area of Science:

  • Cell Biology
  • Molecular Biology
  • Biochemistry

Background:

  • Nuclear import and export proteins play crucial roles in regulating cellular processes.
  • Exportins, a class of nuclear transport receptors, are known to mediate the transport of specific cargo proteins from the nucleus to the cytoplasm.
  • The function of exportins in regulating the condensation of nuclear proteins and the formation of nuclear bodies remains largely unexplored.

Purpose of the Study:

  • To investigate the interaction between exportin CRM1 and the nuclear protein NPAT.
  • To elucidate the mechanism by which CRM1 affects NPAT condensation and histone locus body (HLB) formation.
  • To explore the potential of targeting this interaction for therapeutic interventions.

Main Methods:

  • Co-immunoprecipitation assays to detect CRM1-NPAT binding.
  • Immunofluorescence microscopy to visualize HLB formation and NPAT localization.
  • In vitro assays using purified proteins and peptides to study NPAT self-association and condensation.
  • Site-directed mutagenesis to analyze the role of the NES motif in CRM1-NPAT interaction.

Main Results:

  • Exportin CRM1 directly binds to the nuclear protein NPAT.
  • CRM1 mediates the nuclear export of NPAT by targeting a nuclear export signal (NES) within the LisH domain.
  • The LisH domain of NPAT is essential for its self-association and condensation, which is inhibited by CRM1's competitive occupation of the NES motif.
  • CRM1 mutants defective in NPAT binding failed to regulate NPAT condensation and HLB remodeling.
  • A designed peptide mimicking the LisH domain disrupted NPAT condensation and HLB formation.

Conclusions:

  • Exportin CRM1 regulates NPAT condensation and HLB formation through a competitive occupation mechanism.
  • This study reveals a novel role for exportins in controlling nuclear protein condensation.
  • The findings provide insights into the regulation of histone transcription and suggest potential therapeutic strategies targeting CRM1-NPAT interactions.

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