The trithorax group (trxG) of activators and Polycomb group (PcG) of repressors 
are believed to control the expression of several key developmental regulators 
by changing the structure of chromatin. Here, we have sought to dissect the 
requirements for transcriptional activation by the Drosophila trxG protein 
Zeste, a DNA-binding activator of homeotic genes. Reconstituted transcription 
reactions established that the Brahma (BRM) chromatin-remodeling complex is 
essential for Zeste-directed activation on nucleosomal templates. Because it is 
not required for Zeste to bind to chromatin, the BRM complex appears to act 
after promoter binding by the activator. Purification of the Drosophila BRM 
complex revealed a number of novel subunits. We found that Zeste tethers the BRM 
complex via direct binding to specific subunits, including trxG proteins Moira 
(MOR) and OSA. The leucine zipper of Zeste mediates binding to MOR. 
Interestingly, although the Imitation Switch (ISWI) remodelers are potent 
nucleosome spacing factors, they are dispensable for transcriptional activation 
by Zeste. Thus, there is a distinction between general chromatin restructuring 
and transcriptional coactivation by remodelers. These results establish that 
different chromatin remodeling factors display distinct functional properties 
and provide novel insights into the mechanism of their targeting.