Brca2, Pds5 and Wapl differentially control cohesin chromosome association and function

Area of Science:

• Molecular Biology
• Cell Biology
• Genetics

Background:

• The cohesin complex is crucial for accurate chromosome segregation during cell division by maintaining sister chromatid cohesion.
• Cohesin also plays roles in DNA repair and gene transcription, with loading and removal mediated by specific protein complexes.
• Pds5 is known for cohesin removal but also has essential roles in sister chromatid cohesion, and its interaction with DNA repair protein Brca2 suggests broader functions.

Purpose of the Study:

• To investigate the roles of Brca2 and Pds5 in sister chromatid cohesion beyond their known functions.
• To elucidate the mechanisms by which Brca2 and Pds5 influence cohesin binding to DNA replication origins and gene regulatory elements.
• To determine the impact of Brca2, Pds5, and Wapl on gene expression in the context of cohesin's functions.

Main Methods:

• Assaying precocious sister chromatid separation in cultured cells depleted of Brca2 and Pds5.
• Genome-wide chromatin immunoprecipitation to map cohesin subunit (SA) binding sites.
• RNA sequencing (RNA-seq) to analyze gene expression changes.

Main Results:

• Brca2 opposes Pds5 function in maintaining sister chromatid cohesion.
• Pds5 facilitates SA cohesin subunit association with DNA replication origins, while Brca2 inhibits this binding.
• Pds5 and Wapl, but not Brca2, restrict the spread of cohesin from origins, influencing gene regulatory element binding.
• Brca2, Pds5, and Wapl collectively impact the expression of many genes involved in Nipped-B and cohesin pathways.

Conclusions:

• Brca2 has novel functions in regulating sister chromatid cohesion and gene expression, extending beyond its established role in DNA repair.
• The study expands the understanding of how accessory proteins modulate the diverse functions of the cohesin complex.
• These findings highlight a complex interplay between DNA repair proteins and the cohesin machinery in maintaining genome stability and regulating gene activity.