A basic motif anchoring ISWI to nucleosome acidic patch regulates nucleosome spacing

Area of Science:

• Molecular Biology
• Chromatin Biology
• Epigenetics

Background:

• ATP-dependent chromatin remodelers are crucial for gene regulation.
• The nucleosome acidic patch is implicated in remodeler activity.
• ISWI remodelers, including SNF2h, are key players in chromatin organization.

Purpose of the Study:

• To identify specific interactions between ISWI remodelers and nucleosomes.
• To investigate the role of a conserved basic motif in SNF2h.
• To understand how cancer-associated histone mutations affect chromatin remodeling.

Main Methods:

• Photocrosslinking-based nucleosome profiling (photoscanning) was employed.
• Biochemical reconstitution assays and cellular studies were performed.
• Kinetic studies with 'Janus' nucleosomes were conducted.

Main Results:

• A conserved basic motif in SNF2h was identified, engaging the nucleosome acidic patch.
• This motif is essential for SNF2h chromatin remodeling activity in vitro and in vivo.
• Cancer-associated histone mutations disrupt chromatin structure via ISWI-mediated unidirectional nucleosome sliding.

Conclusions:

• The basic motif in SNF2h is critical for anchoring the remodeler to nucleosomes.
• Oncogenic histone mutations can alter chromatin landscape by affecting nucleosome positioning.
• This provides a mechanistic link between histone mutations and chromatin dysregulation in cancer.