MATURATION STAGE AND PROLIFERATION-DEPENDENT EXPRESSION OF DUTPASE INHUMAN T-CELLS

We have developed a database of lymphoid polypeptides detected by two- dimensional polyacrylamide gel electrophoresis to aid in studies of le ukemogenesis and of mutation affecting protein structure. In prior stu dies, we observed a 19-kDa phosphopolypeptide which was induced with p roliferation in mature T cells and constitutively expressed in immatur e thymocytes. In this report we describe the identification of this po lypeptide as the phosphorylated form of dUTPase (EC 3.6.1.23), followi ng cDNA cloning of the gene, based on a partial amino acid sequence of the phosphopolypeptide. Studies of the expression and phosphorylation of dUTPase in human T cells indicate that accumulation and phosphoryl ation of dUTPase in mature T cells occur in a cell cycle-dependent man ner. Interestingly, noncycling immature thymocytes express constitutiv ely high levels of phosphorylated and unphosphorylated dUTPase. These results suggest an important role for dUTPase in immature thymocytes t hat is independent of proliferation.