A DROSOPHILA HOMOLOG OF THE YEAST ORIGIN RECOGNITION COMPLEX

Genes from Drosophila melanogaster have been identified that encode pr oteins homologous to Orc2p and Orc5p of the Saccharomyces cerevisiae o rigin recognition complex (ORC). The abundance of the Drosophila Orc2p homolog DmORC2 is developmentally regulated and is greatest during th e earliest stages of embryogenesis, concomitant with the highest rate of DNA replication. Fractionation of embryo nuclear extracts revealed that DmORC2 is found in a tightly associated complex with five additio nal polypeptides, much like the yeast ORC. These studies will enable d irect testing of the initiator-based model of replication in a metazoa n.