Structure of nucleosome core particles containing uH2A (A24)

Area of Science:

• Chromatin biology
• Histone modifications
• Nucleosome structure

Background:

• Histone variants play crucial roles in regulating gene expression and DNA processes.
• Ubiquitinylation of histone H2A (uH2A) is a key post-translational modification linked to various cellular functions.
• Understanding the structural impact of uH2A incorporation into nucleosomes is essential.

Purpose of the Study:

• To investigate the structural and functional consequences of incorporating uH2A into nucleosomes.
• To determine if uH2A affects nucleosome core particle structure and DNA accessibility.
• To assess the binding of High Mobility Group (HMG) proteins to uH2A-containing nucleosomes.

Main Methods:

• Purification of uH2A and its reconstitution into nucleohistone particles.
• Preparation of uH2A-containing core particles via nuclease digestion.
• DNase I digestion assays to assess DNA accessibility.
• Electrophoretic mobility shift assays (EMSAs) to study HMG protein binding.

Main Results:

• Two molecules of uH2A can be accommodated within a single nucleosome core particle.
• The presence of uH2A does not significantly alter the DNase I digestion pattern or rate compared to H2A-containing particles.
• HMG proteins 14 and 17 demonstrate binding capability to uH2A-containing core particles.

Conclusions:

• uH2A has a minimal impact on the structural integrity of individual nucleosomes.
• Nucleosome structure remains largely unaffected by uH2A incorporation at the individual nucleosome level.
• uH2A-containing nucleosomes are compatible with the binding of regulatory proteins like HMG 14 and 17.