Cloning of a cDNA encoding a rat DNase II-like acid DNase

DNase II is a well-known deoxyribonuclease (DNase) that catalyzes the hydrolysis of DNA into oligonucleotides under acidic conditions. We have identified a novel DNase that shows homology to DNase II, named DLAD, from a search of an expressed sequence tag data base. The full-length cDNA for rat DLAD cloned by polymerase chain reaction encodes a 356-amino acid polypeptide containing a putative N-terminal signal peptide and 5 potential N-glycosylation sites; there is a predicted catalytic domain resemblance to rat DNase II. The predicted DLAD translation product shares 32.9% identity with DNase II. Interestingly, expression of the DRAD mRNA is highly restricted to the liver. A Myc-His tagged recombinant DLAD recovered mainly from the cytoplasm of transfected HeLa S3 cells has a divalent cation-independent DNase activity. The DLAD activity prefers acidic conditions to neutral. The recombinant protein expressed in HeLa S3 cells inhibits the expression of GFP- and lac Z-expression vectors, suggesting that DLAD may play a role in elimination of exogenous DNA. Identification of the full-length cDNA for DLAD would lead to an understanding of the physiology of this DNase II-like molecule.