Molecular Cloning and Expression of cDNA for Human RNase H

Abstract

We have cloned, expressed, and purified to electrophoretic homogeneity a human RNase H. The enzyme has a molecular weight of 32 kDa, is Mg²⁺ dependent, and is inhibited by Mn²⁺ and N-ethylmaleimide. Its molecular weight and cleavage characteristics are consistent with type 2 human RNase H. The human RNase H we have cloned is highly homologous to Escherichia coli RNase HI (33.6% amino acid identity) and to other RNase H enzymes homologous to E. coli RNase HI. The enzyme is encoded by a single gene that is at least 10 kb in length and is expressed ubiquitously in human cells and tissues.