Nishijima Hitoshi, Nishitani Hideo, Saito Noriko, Nishimoto Takeharu
Department of Molecular Biology, Graduate School of Medical Science, Kyushu University, 3-1-1 Maidashi, Higashi-ku, Fukuoka 812-8582, Japan.
Genes Cells. 2003 May;8(5):423-35. doi: 10.1046/j.1365-2443.2003.00644.x.
Both caffeine and the inactivation of RCC1, the guanine-nucleotide exchange factor (GEF) of Ran, induce premature chromatin condensation (PCC) in hamster BHK21 cells arrested in the S-phase, suggesting that RCC1 is a target for caffeine.
Caffeine inhibited the Ran-GEF activity of RCC1 by preventing the binary complex formation of Ran-RCC1. Inhibition of the Ran-GEF activity of RCC1 by caffeine and its derivatives was correlated with their ability to induce PCC. Since caffeine is a derivative of xanthine, the bases and nucleosides were screened for their ability to inhibit RCC1. Adenine, adenosine, and all of the 2'-deoxynucleosides inhibited the Ran-GEF activity of RCC1; however, only adenine and 2'-deoxyadenosine (2'-dA) induced PCC. A factor(s) other than RCC1, should therefore be involved in PCC-induction. We found that both adenine and 2'-dA, but none of the other 2'-deoxynucleosides, inhibited the kinase activity of ATR, similar to that of caffeine. The ATR pathway was also abrogated by the inactivation of RCC1 in tsBN2 cells.
The effect of caffeine on cell-cycle control mimics the biological effect of adenine and 2'-dA, both of which inhibit ATR. dATP, a final metabolite of adenine and 2'-dA, is suggested to inhibit ATR, resulting in PCC.
咖啡因以及Ran的鸟嘌呤核苷酸交换因子（GEF）RCC1的失活，均可在停滞于S期的仓鼠BHK21细胞中诱导早熟染色质凝聚（PCC），这表明RCC1是咖啡因的一个作用靶点。
咖啡因通过阻止Ran-RCC1二元复合物的形成，抑制了RCC1的Ran-GEF活性。咖啡因及其衍生物对RCC1的Ran-GEF活性的抑制作用，与其诱导PCC的能力相关。由于咖啡因是黄嘌呤的衍生物，因此对碱基和核苷抑制RCC1的能力进行了筛选。腺嘌呤、腺苷以及所有2'-脱氧核苷均抑制了RCC1的Ran-GEF活性；然而，只有腺嘌呤和2'-脱氧腺苷（2'-dA）诱导了PCC。因此，PCC诱导过程中应该涉及RCC1以外的其他因子。我们发现，腺嘌呤和2'-dA均抑制了ATR的激酶活性，而其他2'-脱氧核苷均无此作用，这与咖啡因的作用类似。在tsBN2细胞中，RCC1的失活也消除了ATR信号通路。
咖啡因对细胞周期调控的影响模拟了腺嘌呤和2'-dA的生物学效应，二者均抑制ATR。腺嘌呤和2'-dA的最终代谢产物dATP被认为可抑制ATR，从而导致PCC。
