• The ATRX ADD domain directly binds to the histone variant macroH2A-H2B, expanding its known interaction partners beyond histone H3K9me3.
• Structural analysis using AlphaFold2-multimer reveals the molecular basis of macroH2A1-H2B recognition by the ATRX ADD domain.
• The interaction is mediated by the histone-fold domain of macroH2A-H2B, not the macro domain, and is conserved for both macroH2A1 and macroH2A2.
• These findings have implications for understanding ATRX-related diseases and chromatin regulation, potentially informing therapeutic strategies.