Splicing regulates NAD metabolite binding to histone macroH2A

Area of Science:

• Biochemistry
• Molecular Biology
• Epigenetics

Background:

• Histone macroH2A is a key component of mammalian heterochromatin.
• The macro domain is a conserved protein module found in various cellular proteins.

Purpose of the Study:

• To investigate the interaction between human macroH2A1.1 and its potential binding partners.
• To elucidate the structural basis of metabolite recognition by the macro domain.
• To explore the functional consequences of alternative splicing in macroH2A variants.

Main Methods:

• X-ray crystallography to determine the 1.6-Å crystal structure of macroH2A1.1 bound to O-acetyl-ADP-ribose (OAADPR).
• Site-directed mutagenesis to identify key residues involved in metabolite binding.
• Analysis of alternative splicing events in the H2AFY gene.

Main Results:

• Human macroH2A1.1 directly binds the SirT1-metabolite O-acetyl-ADP-ribose (OAADPR) through its macro domain.
• The crystal structure reveals specific molecular interactions for OAADPR recognition.
• Alternative splicing generates macroH2A1.2, which exhibits altered tissue distribution and lacks nucleotide-binding capability.
• Structural differences between macroH2A1.1 and macroH2A1.2 are subtle but abolish metabolite binding in macroH2A1.2.

Conclusions:

• The macro domain of macroH2A1.1 is a functional binding site for OAADPR.
• Alternative splicing of H2AFY provides a mechanism to regulate the interaction of macroH2A variants with nicotinamide adenine dinucleotide (NAD) metabolites.
• This regulation may influence the role of chromatin-associated proteins in response to metabolic changes.