Gao S, Scott R E
Department of Pathology, University of Tennessee Health Science Center, Memphis, Tennessee 38163, USA.
J Cell Physiol. 2003 Dec;197(3):445-52. doi: 10.1002/jcp.10381.
The stable overexpression of near full-length P2P-R protein in human Saos 2 cells restricts cell cycle progression by inducing mitotic arrest at prometaphase and mitotic apoptosis (Gao and Scott, 2002). Those effects of P2P-R were observed in Saos-2 cells that lack p53 and employ a caspase-3-dependent apoptotic signaling pathway. The current studies were performed to evaluate if overexpression of specific segments of the P2P-R protein promote apoptosis in human MCF-7 cells that contain p53 and employ a different apoptotic signaling pathway. Since segments of P2P-R were found not to induce apoptosis independently, the ability of three different P2P-R segments to promote camptothecin-induced apoptosis was evaluated following their stable transfection and expression in MCF-7 cells. Relative to full-length P2P-R (1-1560 aa), the three P2P-R segments used in these studies included: P2P-R-2 (761-1560 aa), P2P-R-3 (1156-1560 aa), and P2P-R-4 (1314-1560 aa). The results document that overexpression of P2P-R-2 and P2P-R-3 promotes camptothecin-induced apoptosis by three to fivefold when assayed by flow cytometric analysis of apoptotic sub 2n cell populations or by TUNEL assays. In contrast, P2P-R-4 had no effect on apoptosis. These results suggest that the ability of P2P-R to promote camptothecin-induced apoptosis in MCF-7 cells involves a specific region (1156-1314 aa) that exists within P2P-R. The data presented also show that the p53 binding domain of P2P-R overlaps with the apoptosis-associated region and previous studies documented that this region of P2P-R also binds single-strand nucleotides (Witte and Scott, 1997). Therefore, P2P-R-promoted apoptosis induced by camptothecin may be influenced by such interactions.
在人Saos 2细胞中近全长P2P-R蛋白的稳定过表达通过诱导有丝分裂前期的有丝分裂停滞和有丝分裂凋亡来限制细胞周期进程（高和斯科特，2002年）。在缺乏p53并采用caspase-3依赖性凋亡信号通路的Saos-2细胞中观察到了P2P-R的这些作用。进行当前研究以评估P2P-R蛋白特定片段的过表达是否能促进含有p53并采用不同凋亡信号通路的人MCF-7细胞中的凋亡。由于发现P2P-R的片段不能独立诱导凋亡，因此在MCF-7细胞中稳定转染并表达三种不同的P2P-R片段后，评估了它们促进喜树碱诱导凋亡的能力。相对于全长P2P-R（1-156阗），这些研究中使用的三种P2P-R片段包括：P2P-R-2（761-156阗）、P2P-R-3（1156-156阗）和P2P-R-4（1314-156阗）。结果表明，当通过对亚2n凋亡细胞群体进行流式细胞术分析或通过TUNEL检测时，P2P-R-2和P2P-R-3的过表达可将喜树碱诱导的凋亡促进三到五倍。相比之下，P2P-R-4对凋亡没有影响。这些结果表明，P2P-R在MCF-7细胞中促进喜树碱诱导凋亡的能力涉及P2P-R中存在的一个特定区域（1156-1314阗）。所呈现的数据还表明，P2P-R的p53结合结构域与凋亡相关区域重叠，并且先前的研究表明P2P-R的该区域也结合单链核苷酸（威特和斯科特，1997年）。因此，喜树碱诱导的P2P-R促进的凋亡可能受此类相互作用的影响。
