DrosophilaFACT contributes toHoxgene expression through physical and functional interactions with GAGA factor

Abstract

Chromatin structure plays a critical role in the regulation of transcription.DrosophilaGAGA factor directs chromatin remodeling to its binding sites. We show here thatDrosophilaFACT (facilitateschromatintranscription), a heterodimer of dSPT16 and dSSRP1, is associated with GAGA factor through its dSSRP1 subunit, binds to a nucleosome, and facilitates GAGA factor-directed chromatin remodeling. Moreover, genetic interactions betweenTrithorax-likeencoding GAGA factor andspt16implicate the GAGA factor–FACT complex in expression ofHoxgenesUltrabithorax, Sex combs reduced, andAbdominal-B. Chromatin immunoprecipitation experiments indicated the presence of the GAGA factor–FACT complex in the regulatory regions ofUltrabithoraxandAbdominal-B.These data illustrate a crucial role of FACT in the modulation of chromatin structure for the regulation of gene expression.