Zinc finger transcription factor INSM1 interrupts cyclin D1 and CDK4 binding and induces cell cycle arrest

Area of Science:

• Molecular Biology
• Cell Biology
• Cancer Research

Background:

• Insulinoma-associated protein 1 (INSM1) is a zinc finger transcription factor crucial for pancreatic beta-cell development.
• Understanding INSM1's role in cell fate determination requires investigating its impact on cell cycle regulation.

Purpose of the Study:

• To elucidate the mechanism by which INSM1 influences cell cycle function and proliferation.
• To identify the specific domains of INSM1 involved in its interaction with cell cycle regulators.

Main Methods:

• Utilized competitive pull-down and co-immunoprecipitation assays to determine INSM1 binding interactions.
• Employed an inducible Tet-on system in Cos-7 and Panc-1 cells for controlled INSM1 expression.
• Assessed cellular proliferation using MTT assays, soft agar colony formation, and in vivo tumor growth studies in nude mice.

Main Results:

• INSM1 binds to the cyclin box of cyclin D1, disrupting its association with CDK4 and leading to retinoblastoma protein hypophosphorylation.
• Ectopic INSM1 expression induced cell cycle arrest, which was reversible by co-expression of cyclin D1 and CDK4.
• The proline-rich N-terminal region of INSM1 is essential for cyclin D1 binding and subsequent cell cycle arrest.
• INSM1 overexpression inhibited Panc-1 cell proliferation and tumor growth in vivo.

Conclusions:

• INSM1 directly interacts with cyclin D1, interfering with cell cycle signaling pathways.
• INSM1 functions as a negative regulator of cellular proliferation, suggesting its potential as a therapeutic target in relevant cancers.