FUNCTIONAL-CHARACTERIZATION OF RNASE H1 FROM DROSOPHILA-MELANOGASTER

We have cloned and functionally characterized the RNase H1 gene from D . melanogaster. The longest open reading frame consists of 5 exons tha t encode a 333 amino acid protein with a molecular mass of 37.1 kDa. T his is the first demonstration of specific nuclease activity of a clon ed RNase gene from a multicellular higher eukaryote. No additional pro teins or cofactors are required for this nuclease activity. Comparison of Drosophila RNase H1 amino acid sequence to that of other cellular eukaryotic homologs reveals the presence of three evolutionarily disti nct domains. The N- and C-terminal conserved domains are connected by a highly variable domain. The C-terminal domain has high amino acid si milarity to bacterial RNase HI and the RNase H domain of retroviral re verse transcriptase, while the N-terminus, of unknown function, is sim ilar to the P6 translational activator of caulimo-viruses. (C) 1997 Ac ademic Press.