The results show that depending on the fiberconfiguration (linker DNA length and NFRs), the histone fold domainof macroH2A1 can either increase or decrease chromatin compaction.This dual potential agrees with gene expression studies showing thatmacroH2A1 can activate or repress genes,25,26 and that in HD, some genes of neuronal and glial cells increasetheir expression while others decrease it.6 The precise values of NRL and NFRs in the genes activated by macroH2Aversus repressed is unknown. Here, MACROH2A1 is linked to Huntington disease.