Recent advances highlight two important chromatin remodeling systems i
nvolved in the transcriptional process. One system includes several me
mbers of the evolutionarily conserved SWI2/SNF2 family found in distin
ct multiprotein complexes with ATP-dependent nucleosome destabilizing
activity; the other is the enzymatic system that governs histone acety
lation and deacetylation. Identification of the catalytic subunits of
these opposing histone-modifying activities reveal conserved proteins
defined genetically as transcriptional regulators.