FOXM1 binds directly to non-consensus sequences in the human genome

Area of Science:

• Molecular Biology
• Cancer Research
• Epigenetics

Background:

• FOXM1 is a key cell cycle regulator overexpressed in many cancers.
• While FOXM1 binds DNA motifs in vitro, genome-wide studies show limited motif enrichment, suggesting alternative recruitment.
• This study investigates direct vs. indirect DNA binding in FOXM1 chromatin recruitment.

Purpose of the Study:

• To determine the necessity of the FOXM1 DNA binding domain for chromatin recruitment.
• To explore the mechanism of FOXM1 chromatin association.

Main Methods:

• In vitro fluorescence polarization assays to identify FOXM1 DNA binding mutants.
• Chromatin immunoprecipitation sequencing (ChIP-seq) using wild-type and DNA binding-deficient FOXM1.
• Proteome-wide interaction analysis.

Main Results:

• Mutations in the FOXM1 DNA binding domain significantly inhibit binding to consensus FKH sequences.
• Genome-wide mapping confirms that FOXM1 DNA binding domain interaction with DNA is essential for chromatin recruitment.
• Reduced FOXM1 recruitment in mutants is not due to altered protein-protein interactions.

Conclusions:

• A functional FOXM1 DNA binding domain is critical for its chromatin recruitment.
• FOXM1 protein-protein interactions and phosphorylation patterns remain largely unaffected by loss of DNA binding.
• FOXM1 is likely recruited to chromatin through co-factor interactions, binding non-canonical DNA sequences.