A putative N-terminal nuclear export sequence is sufficient for Mps1 nuclear exclusion during interphase

Area of Science:

• Cell Biology
• Molecular Biology

Background:

• Mps1 is crucial for the mitotic checkpoint and interphase regulation, including DNA damage response and centrosome duplication.
• Mps1 primarily localizes to the cytoplasm but enters the nucleus in late G2 phase.
• The mechanism of Mps1 nuclear-cytoplasmic shuttling remained unclear.

Purpose of the Study:

• To elucidate the mechanism of Mps1 nuclear export during interphase.
• To identify the specific sequence responsible for Mps1 translocation.

Main Methods:

• Inhibition of Crm1 with Leptomycin B to assess Mps1 export.
• Co-immunoprecipitation to detect Mps1-Crm1 association.
• Bioinformatic analysis to identify potential nuclear export sequences (NES).
• Site-directed mutagenesis to disrupt the putative NES motif.
• Fluorescent protein tagging (EGFP) to visualize subcellular localization.

Main Results:

• Mps1 export from the nucleus to the cytoplasm is a dynamic, Crm1-dependent process.
• A direct association between Mps1 and the export receptor Crm1 was confirmed.
• A novel N-terminal putative nuclear export sequence (pNES) in Mps1 was identified.
• Mutating the pNES motif resulted in altered subcellular distribution, with the mutant protein showing diffused localization instead of predominant cytoplasmic residency.

Conclusions:

• The identified pNES sequence is sufficient to mediate Mps1 export from the nucleus during interphase.
• This discovery clarifies a critical aspect of Mps1 regulation and nuclear transport.