Department of Biological Sciences, Virginia Polytechnic Institute and State University, Blacksburg, VA 246021, USA.
Proteomics. 2013 Jan;13(1):48-60. doi: 10.1002/pmic.201200188.
The biological processes that unfold during the G1-phase of the cell cycle are dependent on extracellular mitogenic factors that signal the cell to enter a state of quiescence, or commit to a cell-cycle round by passing the restriction point (R-point) and enter the S-phase. Unlike normal cells, cancer cells evolved the ability to evade the R-point and continue through the cell cycle even in the presence of extensive DNA damage or absence of mitogenic signals. The purpose of this study was to perform a quantitative proteomic evaluation of the biological processes that are responsible for driving MCF-7 breast cancer cells into division even when molecular checkpoints such as the G1/S R-point are in place. Nuclear and cytoplasmic fractions of the G1 and S cell-cycle phases were analyzed by LC-MS/MS to result in the confident identification of more than 2700 proteins. Statistical evaluation of the normalized data resulted in the selection of proteins that displayed twofold or more change in spectral counts in each cell state. Pathway mapping, functional annotation clustering, and protein interaction network analysis revealed that the top-scoring clusters that could play a role in overriding the G1/S transition point included DNA damage response, chromatin remodeling, transcription/translation regulation, and signaling proteins.
细胞周期 G1 期发生的生物过程取决于细胞外有丝分裂原因子，这些因子信号使细胞进入静止状态，或者通过限制点（R 点）进入细胞周期的 S 期，从而促使细胞周期完成一轮循环。与正常细胞不同，癌细胞进化出了逃避 R 点的能力，即使存在广泛的 DNA 损伤或缺乏有丝分裂信号，它们也能继续通过细胞周期。本研究的目的是对负责驱动 MCF-7 乳腺癌细胞分裂的生物学过程进行定量蛋白质组学评估，即使在 G1/S R 点等分子检查点存在的情况下也是如此。通过 LC-MS/MS 分析 G1 和 S 细胞周期相的核和细胞质部分，从而能够可靠地鉴定出 2700 多种蛋白质。对归一化数据的统计评估导致选择了在每种细胞状态下光谱计数变化超过两倍的蛋白质。途径映射、功能注释聚类和蛋白质相互作用网络分析表明，可能在超越 G1/S 转换点方面发挥作用的得分最高的聚类包括 DNA 损伤反应、染色质重塑、转录/翻译调控和信号蛋白。
