Yamato K, Hashimoto S, Okahashi N, Ishisaki A, Nonaka K, Koseki T, Kizaki M, Ikeda Y, Nishihara T
Department of Molecular Cellular Oncology/Microbiology, Tokyo Medical and Dental University, School of Dentistry, Japan.
Exp Cell Res. 2000 May 25;257(1):198-205. doi: 10.1006/excr.2000.4876.
We have previously found that bone morphogenetic protein-2 (BMP-2), a member of the transforming growth factor-beta family, induces cell-cycle arrest in the G1 phase and apoptotic cell death of HS-72 mouse hybridoma cells. In this study, we show that BMP-2 did not alter expression of cyclin D, cyclin E, cyclin-dependent kinase 2 (CDK2), CDK4, p27KIP1, p16INK4a, or p15INK4b, but enhanced expression of p21(CIP1/WAF1). Accumulation of p21(CIP1/WAF1) resulted in increased binding of p21(CIP1/WAF1) to CDK4 and concomitantly caused a profound decrease in the in vitro retinoblastoma protein (Rb) kinase activity of CDK4. Furthermore, the ectopic expression of human papilloma virus type-16 E7, an inhibitor of p21(CIP1/WAF1) and Rb, reverted G1 arrest induced by BMP-2. Expression of E6/E7, without increasing the p53 level, blocked inhibition of Rb phosphorylation and G1 arrest, but did not attenuate cell death in BMP-treated HS-72 cells. Taken together, these results suggest that inhibition of Rb phosphorylation by p21(CIP1/WAF1) is responsible for BMP-2-mediated G1 arrest and that BMP-2-induction of apoptosis might be independent of Rb hypophosphorylation.
我们之前发现，转化生长因子-β家族成员骨形态发生蛋白-2（BMP-2）可诱导HS-72小鼠杂交瘤细胞在G1期发生细胞周期停滞及凋亡性细胞死亡。在本研究中，我们发现BMP-2并未改变细胞周期蛋白D、细胞周期蛋白E、细胞周期蛋白依赖性激酶2（CDK2）、CDK4、p27KIP1、p16INK4a或p15INK4b的表达，但增强了p21（CIP1/WAF1）的表达。p21（CIP1/WAF1）的积累导致p21（CIP1/WAF1）与CDK4的结合增加，并同时导致CDK4的体外视网膜母细胞瘤蛋白（Rb）激酶活性显著降低。此外，人乳头瘤病毒16型E7（一种p21（CIP1/WAF1）和Rb的抑制剂）的异位表达可逆转BMP-2诱导的G1期停滞。E6/E7的表达在不增加p53水平的情况下，可阻断对Rb磷酸化的抑制和G1期停滞，但不会减弱BMP处理的HS-72细胞中的细胞死亡。综上所述，这些结果表明p21（CIP1/WAF1）对Rb磷酸化的抑制作用是BMP-2介导的G1期停滞的原因，且BMP-2诱导的凋亡可能独立于Rb低磷酸化。
