Exonuclease VII is a single stranded specific deoxynibonuclease which cna degrade denatured DNA, single stranded regions extending from from the termini of duplex DNA, or displaced single stranded regions. It is composed of two non-identical subunits, the genes being in different regions of the chromosome. It is proposed here to express and purify large quanties of the enzyme, study the cellular regulation of its production, and examine the cellular effects of its deficiency. The availability of large quantities of the enzyme will allow detailed mechanistic and functional studies to begin. Having the cloned genes which encode the two subunits makes possible studies of the transcriptional regulation of the genes. The analysis of mutations may provide further insight into the role the enzyme plays in cellular metabolism. Nucleases are among the most abundant and diverse group of enzymes participating in nucleic acid metabolism. It is perfectly obvious in paper models of many DNA and RNA metabolic processes what a variety of functions these enzymes should do. In actual fact, the cellular roles of only a few such enzymes are understood. E. coli exonuclease VII is one that is not. Its enzymatic properties suggest it will be an extremely useful reagent for the specific removal of single-stranded termini from duplex DNA molecules. Dr. Chase was the discoverer of Exonuclease VII and is certainly will prepared to reinitiate this study.
