Mitoinhibitory effects of the tumor promoter 2-acetylaminofluorene in rat liver:: loss of E2F-1 and E2F-3 expression and cdk 2 kinase activity in late G1
Mitoinhibitory effects of the tumor promoter 2-acetylaminofluorene in rat liver:: loss of E2F-1 and E2F-3 expression and cdk 2 kinase activity in late G1
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DOI：
10.1016/j.jhep.2004.02.028
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发表时间：
2004-06-01
影响因子：
25.7
通讯作者：
Porsch-Hällström, I
中科院分区：
文献类型：
--
作者：
Ohlson, LCE;Koroxenidou, L;Porsch-Hällström, I
背景/目标：方法：采用cdk 2激酶法检测组蛋白H1的磷酸化水平，观察肝癌促进剂2-乙酰氨基芴（2-AAF）对肝癌细胞增殖的抑制作用。cdk 4激酶测定，以检查是否形成能够磷酸化Rb的活性cdk 4/细胞周期蛋白D复合物。结果：AAF处理后，cdk 4激酶介导的Rb磷酸化水平增加。转录因子E2 F-1和E2 F-3的核表达下调，而E2 F-4则减少。2-AAF处理还显著降低了G1/S-转换期间cdk 2激酶活性/组蛋白H1磷酸化。Western blot显示2-AAF处理后细胞核和细胞质中cyclin A和cyclin B蛋白均丢失，而Rb蛋白水平在G1期显著升高。在对照肝脏中观察到的细胞周期依赖性核p107蛋白升高，在AAF处理的动物中没有观察到。结论：2-AAF的影响;非常低的cdk 2激酶活性可能会阻止G1/S转变; pRb水平升高，转录因子E2 F-1和-3水平降低，这可能是负责减少E2 F靶基因的表达，如细胞周期蛋白A和E2 F-1。(C)2004年欧洲肝脏研究协会。Elsevier B. V.出版，保留所有权利。
Background/Aims: Examine the mitoinhibitory effect of the liver tumor promoter 2-acetylaminofluorene (2-AAF) in vivo, with focus on the proteins regulating G1- and S progression.Methods: cdk 2 kinase assay to examine histone H1 phosphorylation. cdk 4 kinase assay to examine whether active cdk 4/cyclin D complexes, capable of phosphorylating Rb, are formed. Western blot to monitor protein expression.Results: cdk 4 kinase-mediated Rb phosphorylation was increased by AAF treatment. Nuclear expression of the transcription factors E2F-1 and E2F-3 was downregulated, while E2F-4 was decreased. 2-AAF treatment also markedly reduced cdk 2 kinase activity/histone H1 phosphorylation during G1/S-transition. Western blot showed loss of nuclear as well as cytoplasmic cyclin A and cyclin B protein after 2-AAF treatment, while the Rb protein level was markedly increased during G1. The cell cycle dependent elevation of nuclear p107 protein, seen in control livers, was not observed in AAF-treated animals.Conclusions: Effects of 2-AAF; Very low cdk 2 kinase activity that could possibly block G1/S-transition; increased pRb level together with diminished levels of transcription factors E2F-1 and -3, that could be responsible for reducing the expression of E2F target genes such as cyclin A and E2F-1. (C) 2004 European Association for the Study of the Liver. Published by Elsevier B.V. All rights reserved.