HuCHRAC, a human ISWI chromatin remodelling complex contains hACF1 and twonovel histone-fold proteins

Chromatin remodelling complexes containing the nucleosome-dependent ATPase ISWI were first isolated from Drosophila embryos (NURF, CHRAC and ACF), ISW I was the only common component reported in these complexes. Our purificati on of human CHRAC (HuCHRAC) shows that ISWI chromatin remodelling complexes can have a conserved subunit composition in completely different cell type s, suggesting a conserved function of ISWI, We show that the human homologu es of two novel putative histone-fold proteins in Drosophila CHRAC are pres ent ill HuCHRAC, The two human histone-fold proteins form a stable complex that binds naked DNA but not nucleosomes, HuCHRAC also contains human ACF1 (hACF1), the homologue of Acf1, a subunit of Drosophila ACF, The N-terminus of mouse ACF1 was reported as a heterochromatin-targeting domain, hACF1 is a member of a family of proteins with a related domain structure that all may target heterochromatin. We discuss a possible function for HuCHRAC in h eterochromatin dynamics. HuCHRAC does not contain topoisomerase IT, which w as reported earlier as a subunit of Drosophila CHRAC.