Culture-age effect on uracil-DNA glycosylase activity in normal human skin fibroblasts.

Abstract

Culture-passage dependent change in the activity of uracil-DNA glycosylase, one of DNA repair enzymes, was characterized in cell-free extracts of normal human fibroblasts from phase II through phase III. During phase II, the enzyme activity was proportional to the DNA synthetic activity in random cultures, and synchronized cells showed the elevation of the enzyme activity only during S phase. However, cell populations of presenescent phase III having retarded growth showed a dysregulated substantial increase of the glycosylase activity during G0 and G1 phases. Finally, the enzyme activity decreased as a linear function of population doubling level during the entire phase III. Werner syndrome (WS) cells also showed a rapid decrease in the enzyme activity during phase III. The thermolability of uracil-DNA glycosylase was identical between presenescent and senescent normal and WS cells.