Drosophila Enhancer of zeste protein interacts with dSAP18

The Drosophila Enhancer of zeste [E(z)] gene encodes a member of the Polycomb group of transcriptional repressors. Here we report evidence for direct physical interaction between E(Z) and dSAP18, which previously has been shown to interact with Drosophila GAGA factor and BICOID proteins. dSAP18 shares extensive sequence similarity with a human polypeptide originally identified as a subunit of the SIN3A-HDAC (switch-independent 3-histone deacetylase) co-repressor complex. Yeast two-hybrid and in vitro binding assays demonstrate direct E(Z)-dSAP 18 interaction and show that dSAP 18 is capable of interacting with itself. Co-immunoprecipitation experiments provide evidence for in vivo association of E(Z) and dSAP18. Gel filtration analysis of embryo nuclear extracts shows that dSAP18 is present in native protein complexes ranging from similar to1100 to similar to450 kDa in molecular mass. These studies provide support for a model in which dSAP18 contributes to the activities of multiple protein complexes, and potentially may mediate interactions between distinct proteins and/or protein complexes. (C) 2002 Elsevier Science B.V. All rights reserved.