Study of Scr regulation and insulator function in Drosophila. P. Majumder , H.N. Cai. Cellular Biology, University of Georgia, Athens, GA 30602.

   Chromatin boundary elements or insulators regulate enhancer-promoter interactions in complex genetic loci. The mechanism of insulator action is not known. Previous studies indicate that interactions between insulators and/or other nuclear sites may be essential for insulator function. For example, the activity of the Drosophila suHw insulator is influenced by its cis-arrangement and position relative to the enhancer and promoter elements. We have used a transgenic Drosophila embryo stripe expression assay to examine the interactions among various Drosophila insulators in vivo. Our initial analysis indicates that unlike the homologous suHw-suHw interaction that abolishes the insulator activity, tandem arrangement of suHw and scs insulators enhances their ability to block various enhancers in transgenic embryos. Results from additional combinations between various Drosophila insulator elements will be presented. Insulators or chromatin boundaries have been identified in the Bx-C homeotic gene complex and shown to be important for the regulation of the Abd B gene activity. Evidence will be presented for the study of SF-1 a novel insulator we identified in the Antp-C complex, in regulating Scr and ftz gene activity.