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KMID : 0385220000100010014
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Korean Journal of Gerontology
2000 Volume.10 No. 1 p.14 ~ p.19
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Inhibition of Human Term Placental DNA Topoisomerase I Activity by Dephosphorylation
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Son Mi-Young
Youn Kyung-Ah
Kwak Sang-Tae
Kweon Gi-Ryang
Yon Wan-Hee
Park Seung-Gil
Im Gyu
Hwang Byoung-Doo
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Abstract
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The effects of dephosphorylation on human term placental DNA topoisomerase I (Topo I) activity have been investigated. The Topo I activity reduced to 75, 70, 50 and 10% in comparison with that of control by treatment of 2.5, 5, 10 and 20 units of calf intestinal alkaline phosphatase (CIP) far 30 min treatment, respectively. And the enzyme activity was not changed by treatment of 20 units of CIP for 5 min but dramatically reduced over 10 min. Both purified lope I and dephosphorylated Topo I activity were not changed by protein kinase A-dependent phosphorylation. The inhibitory effects of camptothecin on both purified Topo I and dephosphorylated Topo I were identical. These results suggest that human term placental Topo I may be already phosphorylated and its activity may be regulated by phosphorylation / dephosphorylation. And Topo I might be dephosphorylated preferentially except the domain responsible far the catalytic activity and then dephosphorylated at catalytic domain by phosphatase.
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KEYWORD
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DNA, topoisomerase, I, Placenta, Camptothecin
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