The mammalian ISWI chromatin remodeling complexes contain either one of two related ISWI ATPases, Snf2l and Snf2h [6],[7]. The Snf2l ATPase is contained in two assemblies–NURF (Nucleosome Remodeling Factor), which is dedicated to the regulation of transcription, and the recently reported CERF [8],[9]. NURF is the founding member of the ISWI family of chromatin remodeling complexes, and was originally characterized in Drosophila [10]. Purified Drosophila NURF catalyzes ATP-dependent nucleosome sliding and promotes transcription from chromatin templates in vitro [9]. As shown by whole genome expression studies of mutants, NURF positively or negatively regulates transcription of several hundred Drosophila genes in vivo, including many genes important for fly development [11]. This is likely accomplished through recruitment of NURF301, the largest NURF subunit, by gene-specific transcription factors [11]–[13], and binding of a PHD finger of NURF301 to tri-methylated lysine 4 on histone H3 [14]. Human NURF contains the orthologs of three of four Drosophila NURF components–BPTF (Bromodomain PHD-finger Transcription Factor), the mammalian counterpart of NURF301, SNF2L (the ISWI ATPase) and RbAp46/48, a WD-40 repeat histone-binding protein found in several chromatin-related protein complexes [15]. Biochemical studies of human NURF have shown that it has similar properties to its Drosophila counterpart [15].
