RATIO OF 3' → 5'–EXONUCLEASE AND DNA-POLYMERASE ACTIVITIES IN NORMAL
AND CANCER CELLS OF RODENTS AND HUMANS
T. P. Kravetskaya, N. L. Ronzhina, V. M. Krutyakov
B. P. Konstantinov Petersburg Nuclear Physics Institute RAS,
Division of Molecular and Radiation Biophysics, Gatchina;
e-mail: krut@omrb.pnpi.spb.ru
Mutations in the genes of corrective 3' → 5'–exonucleases as well as in DNA polymerases lead to decrease
in DNA biosynthesis accuracy all over genome. This is accompanied by the increase in mutagenesis and carcinogenesis
probabilities. In this work, the activities of 3' → 5'–exonucleases and DNA polymerases were studied
in the extracts from normal and cancer cells of rodents and humans, and we are the first to measure their integral
ratios. As example, in cultivated dermal fibroblasts of an adult human, the value of the ratio of activities of
3' → 5'–exonucleases to DNA polymerase activity (3'-exo/pol) surpassed several folds the such a value for HeLa
cells. Similar picture was observed during the comparison of normal fibroblasts of rat embryos and transformed
fibroblasts of Chinese hamster A238. Experiments with cell-free extracts of some organs from healthy rats
of various ages have shown that normal proliferating cells demonstrate higher 3' → 5'–exonuclease activity and
higher values of 3'-exo/pol that quiescent cells. Comparison of these data suggests a violation of the function of
corrective 3' → 5'–exonucleases in abnormally growing cancer cells.
Key words: 3' → 5'–exonucleases, normal cells, cancer cells
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