Investigations of Drosophila Suppressor of Hairy-wing zinc-finger mutants identify distinct subclasses of genomic binding sites. Ryan M. Baxley¹, Michael W. Klein², Ashley G. Fell², Joel A. Morales-Rosado², James D. Bullard², Pamela K. Geyer^1,2. 1) Molecular & Cellular Biology Program, University of Iowa; 2) Biochemistry Department, University of Iowa, Iowa City, IA.

   Suppressor of Hairy-wing [Su(Hw)] is a twelve zinc finger (ZnF) DNA binding protein that localizes to ~3,000 genomic regions. While its role in gypsy insulator function is well characterized, its essential function in oogenesis is poorly understood. Our recent investigations demonstrate that loss of Su(Hw) alters transcription of many target genes in the ovary. These findings imply that Su(Hw) is a multi-functional transcription factor, capable of conferring insulator, repressor and activator effects when bound at distinct target sites. The features that contribute to the diverse regulatory functions of Su(Hw) binding sites (SBSs) are unknown. To understand these processes, we performed an EMS mutagenic screen and identified two new su(Hw) mutations that genetically separate Su(Hw) functions. One mutant retains gypsy insulator activity and not female fertility, while a second mutant retains female fertility and not gypsy insulator function. Interestingly, each of these alleles encodes a protein that disrupts a single ZnF, suggesting that the ZnF domain contributes to Su(Hw) regulation. To test this prediction, analyses of genome-wide occupancy of the Su(Hw) ZnF mutants were completed. These studies revealed that the functionally separate ZnF mutants occupy different sequence subclasses of SBSs that show enrichment for different co-factors. These observations suggest that DNA sequence may define the regulatory output of an SBS. These predictions are being tested through functional analyses. Together, our studies provide insights into how multiple regulatory roles are executed by a single DNA binding transcription factor.