Repressive chromatin must be remodeled to allow for transcriptional activat
ion of genes in eukaryotic cells. Factors that alter chromatin structure to
permit access of transcriptional activators, RNA polymerase II and the pol
ymerase-associated general transcription factors to nucleosomal promoter se
quences are as highly conserved as the basic mechanism of transcription. On
e group of promoter restructuring factors that perturbs chromatin in an ATP
-dependent manner includes NURF, CHRAC, ACF, the SWI/SNF complex, and SWI/S
NF-related proteins. Each member of this group contains a subunit homologou
s to the DNA-dependent ATPase; however, their individual mechanisms of acti
on are unique. The small amount of SWI/SNF complex (100-200 copies/cell), i
ts affiliation with a select number of inducible genes, and its interaction
with the glucocorticoid and estrogen receptors, suggests the SWI/SNF compl
ex might be preferentially targeted to active promoters. The SWI/SNF-relate
d family of RUSH proteins which includes RUSH-1 alpha and beta, hHLTF, HIP1
16, Zbu1, P113, and the transcription factor RUSH-la isolog has been implic
ated as a highly conserved DNA binding site-specific ATPase. (C) 1999 Elsev
ier Science Ireland Ltd. All rights reserved.