The carcinogen 2-acetylaminofluorene inhibits activation and nuclear accumulation of cyclin-dependent kinase 2 in growth-induced rat liver
✍ Scribed by Birgitte Lindeman; Ellen Skarpen; Morten P. Oksvold; Henrik S. Huitfeldt
- Publisher
- John Wiley and Sons
- Year
- 2000
- Tongue
- English
- Weight
- 275 KB
- Volume
- 27
- Category
- Article
- ISSN
- 0899-1987
No coin nor oath required. For personal study only.
✦ Synopsis
Growth arrest in G 1 is a common cellular response to DNA damage. In the present study, liver regeneration was combined with continuous exposure for 2-acetylaminofluorene (AAF) to study mechanisms of carcinogen-induced growth arrest in vivo. Growth arrest of uninitiated hepatocytes is central for AAF-induced promotion of premalignant lesions in rat liver. To characterize this growth arrest, we examined the activity of cyclin-dependent kinase (Cdk) 2 in unexposed liver and in AAF-exposed liver after growth induction by partial hepatectomy (PH). Rats were fed either a control diet or an AAF-supplemented diet. After 7 d, a two-third PH was performed and the animals were killed after 0, 12, 18, 24, and 36 h. Kinase assays showed that cyclin E± and Cdk2±associated activities were lower in AAFexposed liver than in unexposed liver after PH. Although the total cellular levels of cyclin E and Cdk2 were similar, cyclin E±Cdk2 assembly was markedly reduced. In unexposed hepatocytes, Cdk2 translocated to the nuclei after PH. Much of the nuclear Cdk2 was in a rapidly migrating form, presumably representing the Thr160-phosphorylated form of Cdk2. In contrast, in AAF-exposed liver both nuclear Cdk2 accumulation and Thr160-phosphorylation of Cdk2 were reduced. Although p53 and p21 waf1/cip1 were induced by AAF, the binding of p21 to cyclin E and Cdk2 was not increased in growth arrested liver. In conclusion, hepatocyte growth arrest caused by AAF exposure was characterized by a lowered Cdk2 activity that was accompanied by a reduced assembly of cyclin E±Cdk2 complexes but not by binding of p21.