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Updated: May 25, 2026
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Myosin-Specific Adaptations of In vitro Fluorescence Microscopy-Based Motility Assays
Published on: February 4, 2021
Specific nuclear localizing sequence directs two myosin isoforms to the cell nucleus in calmodulin-sensitive manner
Rastislav Dzijak1, Sukriye Yildirim, Michal Kahle
1Department of Biology of the Cell Nucleus, Institute of Molecular Genetics of the ASCR, v.v.i., Prague, Czech Republic.
Plos One
|February 2, 2012
Summary
Nuclear myosin I (NM1) and its cytoplasmic counterpart (Myo1c) are imported into the nucleus via a novel nuclear localization sequence. This finding reveals new roles for these molecular motors in nuclear functions.
Area of Science:
- Cell Biology
- Molecular Biology
- Biochemistry
Background:
- Nuclear myosin I (NM1) is a molecular motor in the nucleus involved in transcription and chromatin remodeling.
- NM1 is an isoform of cytoplasmic myosin 1c (Myo1c), differing by a 16-amino acid N-terminal extension.
- This N-terminal stretch was hypothesized to mediate NM1 nuclear import.
Purpose of the Study:
- To elucidate the mechanism of nuclear import for NM1.
- To identify the specific sequence responsible for NM1 nuclear localization.
- To determine the nuclear transport receptors involved in NM1 import.
Main Methods:
- Over-expression of GFP-tagged NM1 mutants.
- Transfection of tagged NM1 and Myo1c constructs.
- Analysis of endogenous Myo1c in knockout mouse cells.
- Pull-down and co-immunoprecipitation assays.
- Calmodulin competition assays.
Main Results:
- A novel nuclear localization sequence (NLS) within the calmodulin-binding motif of NM1 was identified.
- Both NM1 and Myo1c were confirmed to be present in the nucleus.
- Importin beta, importin 5, and importin 7 were identified as nuclear transport receptors for NM1.
- Elevated calmodulin levels interfered with NM1 nuclear import.
Conclusions:
- A novel NLS facilitates the nuclear import of both NM1 and Myo1c.
- This finding expands the known functions of myosin I isoforms within the nucleus.
- It opens new avenues for studying nuclear processes and nucleocytoplasmic transport of molecular motors.
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