RNA plays an important role in cellular regulation--either by its presence in active form or by its total absence. A number of proteins have been shown to be involved in regulating RNA synthesis and RNA processing in Escherichia coli--among these are RNA polymerase, rho and RNase III. We have described an enzyme from chick embryos (RNase DII) which is an analogue of RNase III. These proteins are involved in the synthesis or inhibition of synthesis of specific species of RNA and in the processing of RNA. Another enzyme which may be involved in regulation of RNA synthesis is RNase H. To better understand the nature of this enzyme, we have determined the nucleotide sequences coding for E. coli RNase H and for a mutant of e. coli RNase H. Clones bearing plasmids of the wild-type RNase H gene produce 10-20 x the normal level of enzyme. Analogous clones the mutant gene also produce 10-20 x the normal level of enzyme but with a lower specific activity. The objective of this research project is to determine the method by which several of these enzymes act to regulate RNA synthesis in E. coli and chick embryos.