AN IMPRINTING ELEMENT FROM THE MOUSE H19 LOCUS FUNCTIONS AS A SILENCER IN DROSOPHILA

Genomic imprinting as originally described in Sciara(1) is displayed b y many organisms. In mammals, X-inactivation and the parent-of-origin- specific silencing of imprinted genes are examples of this phenomenon( 2,3). A heritable chromatin structural modification may be the critica l mechanism in such instances of chromosome condensation and preferent ial gene inactivation. H19 is an imprinted gene(4) in which the repres sed paternal allele is hypermethylated and the compacted chromatin is relatively resistant to digestion by nucleases(5-7). In order to uncov er underlying conserved epigenetic mechanisms we have introduced a mou se H19 transgene into Drosophila. We show here that a 1.2-kb H19 upstr eam sequence functions in cis as a parent-of-origin independent silenc ing element in Drosophila. Strikingly, this cis-acting element is loca ted within an upstream region that is necessary for H19 imprinting in mice(8). These results suggest involvement of an evolutionary conserve d mechanism in both gene silencing in Drosophila and imprinting in mic e.