Site-Specific Recognition of a 70-Base-Pair Element Containing d(GA)n Repeats Mediatesbithoraxoid Polycomb Group Response Element-Dependent Silencing

• DOI: 10.1128/mcb.21.14.4528-4543.2001
• Publication Date: 2002-07-27T10:03:53Z
• Authors: Jacob W. Hodgson; Bob Argiropoulos; Hugh W. Brock
• Keywords: Polycomb-group proteins

Polycomb group proteins act through response elements (PREs) to maintain silencing at homeotic loci. The minimal 1.5-kb bithoraxoid (bxd) PRE contains a region required for pairing-sensitive repression and flanking regions maintenance of embryonic silencing. Little is known about the identity specific sequences necessary function regions. Using gel mobility shift analysis, we identify DNA binding activities that interact specifically with multipartite 70-bp fragment (MHS-70) downstream sequence. Deletion MHS-70 in context 5.1-kb bxd element derepresses embryos. A partially purified activity requires multiple, nonoverlapping d(GA)3repeats vitro. Mutation within destabilizes subset cells vivo but gives weaker derepression than deletion MHS-70. These results suggest d(GA)3 repeats are important other also contribute Antibody supershift assays Western analyses show distinct isoforms Polyhomeotic two recognize repeats, TRL/GAGA factor Pipsqueak (Psq), present activity. Mutations Trl psq enhance phenotypes ofph, indicating Psq enhancers which have sequence-specific studies demonstrate site-specific recognition by d(GA) n repeat mediates PcG-dependent