Properties of two nuclease genes in Neurospora crassa

Two genes, nuc-1 and nuc-2, of Neurospora crassa which were responsible for the nucleic acid digestion, were located on linkage group 1 and 2, respectively. A temperature-sensitive mutant (B1ts-2) was obtained from a nuc-2 mutant. Nuclease mutants showed a reduced activity of nuclease N(3) which was found to be a complex consisting of nuclease N(3) (') and inhibitor molecule. Nuclease N(3), nuclease N(3) (') and inhibitor were partially purified and estimated to have the approximate molecular weights of 38,000, 12,500 and 25,000 respectively. A nuc-1 mutant produced the nuclease N(3) (') altered in thermolability. A nuc-2 mutant and B1ts-2 produced the inhibitor altered in the capacity to inhibit nuclease N(3) (') activity. The inhibitor prepared from B1ts-2 was more thermostable than that from other strains. From these results, it was suggested that the nuc-1 gene is the structural gene for nuclease N(3) (') and the nuc-2 gene that for the inhibitor. A possible involvement of this enzyme-inhibitor complex in the regulation of nuclease activity and synthesis of other proteins was suggested.