| Autor: |
P, Giannoni, G, Fronza, L, Scarabelli, E, Fugassa, M, Orunesu, C F, Cesarone |
| Rok vydání: |
1991 |
| Předmět: |
|
| Zdroj: |
Bollettino della Societa italiana di biologia sperimentale. 67(5) |
| ISSN: |
0037-8771 |
| Popis: |
Previous studies have demonstrated that DNA topoisomerase I activity can be closely related to DNA replication and active transcription in different experimental models. This relationship was further investigated by studying the time course of DNA topoisomerase I activity in cultured rat hepatocytes stimulated by epidermal growth factor. This mitogen has been shown to stimulate DNA synthesis in liver cells both in vivo and in vitro. DNA topoisomerase I activity was assayed quantifying ATP-independent relaxation of a negatively supercoiled plasmid, substrate for the enzyme. Incubation of cellular extracts was carried out at 30 degrees C for 15'. Products were electrophoresed and analyzed by densitometry. DNA synthesis was measured as [3H]thymidine incorporation in the hepatocytes, after a 2 hrs pulse labelling. An increase in DNA topoisomerase I activity was observed early after epidermal growth factor addition, before the onset of DNA synthesis. Concomitant administration of orotic acid, which has recently shown mitoinhibitory effect, abolished the EGF-induced activity as well as DNA synthesis. Taken together these data indicate that, in cultured hepatocytes, the induction of DNA synthesis is supported by DNA topoisomerase I with a precise time schedule. Orotic acid administration abolishes this response and causes an overall loss in DNA topoisomerase I activity. |
| Databáze: |
OpenAIRE |
| Externí odkaz: |
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