Structure of the nucleosome-bound human BCL7A

Area of Science:

• Molecular Biology
• Structural Biology
• Genomics

Background:

• The BCL7 family proteins (BCL7A, BCL7B, BCL7C) are recently identified subunits of the mammalian SWI/SNF chromatin remodeler.
• Their function and structural role within the complex are largely unknown, despite their mutation in various cancers, particularly blood malignancies.

Purpose of the Study:

• To elucidate the structural basis of BCL7A interaction with nucleosomes.
• To investigate the functional consequences of cancer-associated BCL7A mutations.
• To understand BCL7A's role in SWI/SNF complex activity and genomic function.

Main Methods:

• Cryo-electron microscopy (cryo-EM) for structural determination.
• Biophysical and biochemical assays to characterize protein-nucleosome interactions.
• Genomic analysis to assess BCL7A's function in vivo.

Main Results:

• BCL7A forms a stable, high-affinity complex with the nucleosome core particle (NCP) via an arginine anchor motif binding to the acidic patch.
• Cancer-associated BCL7A mutations were shown to impair this nucleosome interaction.
• BCL7A was found to contribute to the remodeling activity of the mammalian SWI/SNF (mSWI/SNF) complex and influence its genomic function.

Conclusions:

• The study reveals the structural mechanism of BCL7A binding to nucleosomes, highlighting an arginine anchor interaction with the acidic patch.
• Cancer mutations affecting BCL7A-nucleosome binding provide a rationale for their role in blood malignancies.
• These findings enhance the understanding of SWI/SNF complex chromatin recognition and BCL7 protein function.