DLAD, a novel mammalian divalent cation-independent endonuclease with homology to DNase II

In this report, we describe the molecular cloning and characterization of D LAD, a novel mammalian deoxyribonuclease homologous to DNase II. The full l ength cDNA for mouse DLAD has been cloned by polymerase chain reaction, The cDNA contains a 1065 bp open reading frame (ORF) encoding a 354 amino acid protein with a calculated molecular mass of 40 767. The predicted protein for DLAD shares 34.4% identity with DNase II. DLAD is also homologous to th ree predicted proteins, C07B5.5, F09G8.2 and K04H4.6, from the nematode Cae norhabditis elegans, Furthermore, the third ORF of the fowlpox virus genome is found to encode a DLAD homologue showing 37.1% identity at the amino ac id level, Northern blot analysis reveals that expression of the DLAD mRNA i s highly restricted to the liver. DLAD mainly exists as a cytoplasmic prote in with divalent cation-independent endonuclease activity and cleaves DNA t o produce 3'-phosphoryl/5'-hydroxyl ends. It is active under a wide range o f pH with maximum activity at pH 5.2, Among known DNase inhibitors tested, aurintricarboxylic acid and Zn2+ are found to be effective inhibitors of th e DLAD activity.