Nuclear type I myosins actively support nucleolar and nuclear structure and function
Audrey Yi Tyan Peng1, Jianhui Li2, Brian C Freeman3
1Department of Cell and Developmental Biology, School of Molecular and Cellular Biology, University of Illinois-Urbana-Champaign, Urbana, Illinois USA.
Genes & Development
|August 6, 2026
Summary
Nuclear type I myosins are crucial for maintaining cell structure and function. Their depletion disrupts genome organization, gene expression, and nucleolar activities, highlighting their essential role in nuclear integrity.
Area of Science:
- Cell Biology
- Molecular Biology
- Genomics
Background:
- The nucleus, enclosed by a nuclear envelope, houses the genome and nucleolus.
- Molecular mechanisms maintaining nuclear structure and biomolecular spacing are not fully understood.
- Motor proteins, like myosins, are known for cytoplasmic organization but their nuclear roles are less defined.
Purpose of the Study:
- To investigate the role of nuclear myosin motors in maintaining nuclear organization and function.
- To determine the specific functions of different myosin types (I, II, V) within the nucleus.
Main Methods:
- Depletion of specific nuclear myosin types (I, II, V) using experimental techniques.
- Assessment of 3D genome organization, gene expression, nucleolar structure, and nuclear envelope morphology.
- Analysis of nucleolar function, including rRNA synthesis and processing.
- Tracking the dynamic mobility of nucleolar proteins (Nop1/fibrillarin) and RNA polymerase I.
Main Results:
- Nuclear type I myosins are essential for cell division; types II and V are not.
- Depletion of nuclear type I myosin caused 3D genome disorganization, altered gene expression, nucleolar disruption, and nuclear envelope defects.
- Nucleolar dysfunction, including reduced rRNA synthesis and processing, preceded genome disorganization.
- Altered dynamic mobilities of Nop1 (fibrillarin) and RNA polymerase I were observed upon type I myosin depletion.
Conclusions:
- Nuclear type I myosin is critical for maintaining the shape and function of the nucleolus and the nucleus.
- Type I myosin plays a vital role in coordinating nucleoplasmic biomolecular spacing and nuclear organization.
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