Drosophila taranis is an important mediator of Polycomb mediated transcriptional silencing. Pranabananda Dutta, Willis Li. Medicine, University of California, San Diego, La Jolla, CA.

   The Polycomb group (PcGs) proteins are implicated in epigenetic transcriptional repression in development, stem cell maintenance and tumorigenesis. The molecular mechanism by which PcGs silence target loci is not fully understood. Here we show that Drosophila taranis (tara) is required for positioning Pc to its target genes. Embryos lacking tara exhibit partial homeotic transformation in the cuticular segments, a phenotype associated with Pc mutants. Consistent with the homeotic transformation, tara loss of function results in misexpression of homeotic gene Ultrabithorax (Ubx) and in reduced Pc recruitment on polytene chromosomes. Hence, we show that taranis modulates the spatialexpression pattern of Polycomb target genes during Drosophila development.