MacroH2A1.1 (D5F6N) Rabbit mAb #12455

Histone macroH2A1 and macroH2A2 comprise a family of variant histone H2A proteins. MacroH2A1 exists as two distinct isoforms due to alternative splicing of a single gene; macroH2A1.1 levels accumulate throughout differentiation and development while macroH2A1.2 shows a constant level of expression (1). MacroH2A1 and macroH2A2 are encoded by completely distinct genes located on separate chromosomes (2,3). Both macroH2A1 and macroH2A2 proteins contain an amino-terminal histone-like region with 64% sequence identity to canonical histone H2A, in addition to a carboxy-terminal “macro” domain (1-3). MacroH2A1 and macroH2A2 are enriched in facultative heterochromatin, including inactivated X chromosomes in mammalian females and senescence-associated heterochromatin foci (2-5). Both act to repress gene transcription by inhibiting the binding of transcription factors to chromatin, the acetylation of histones by p300, and the chromatin-remodeling activities of SWI/SNF and ACF (6,7). The macro domain of macroH2A1.1 binds to ADP-ribose and functions to recruit macroH2A1.1 to activated PARP at sites of DNA damage, where it mediates chromatin rearrangements to locally regulate the DNA damage response (8). MacroH2A1.2 and macroH2A2 do not bind poly-ADP-ribose and are not recruited to sites of activated PARP (8).