Matragkou Christina N, Papachristou Eleni T, Tezias Sotirios S, Tsiftsoglou Asterios S, Choli-Papadopoulou Theodora, Vizirianakis Ioannis S
Laboratory of Biochemistry, School of Chemistry, Aristotle University of Thessaloniki, GR-54124 Thessaloniki, Greece.
J Cell Biochem. 2008 Jul 1;104(4):1477-90. doi: 10.1002/jcb.21722.
Evidence now exists to indicate that some ribosomal proteins besides being structural components of the ribosomal subunits are involved in the regulation of cell differentiation and apoptosis. As we have shown earlier, initiation of erythroid differentiation of murine erythroleukemia (MEL) cells is associated with transcriptional inactivation of genes encoding ribosomal RNAs and ribosomal proteins S5 (RPS5) and L35a. In this study, we extended these observations and investigated whether transfection of MEL cells with RPS5 cDNA affects the onset of initiation of erythroid maturation and their entrance in cell cycle arrest. Stably transfected MEL cloned cells (MEL-C14 and MEL-C56) were established and assessed for their capacity to produce RPS5 RNA transcript and its translated product. The impact of RPS5 cDNA transfection on the RPS5 gene expression patterns and the accumulation of RPS5 protein in inducible transfected MEL cells were correlated with their ability to: (a) initiate differentiation, (b) enter cell cycle arrest at G(1)/G(0) phase, and (c) modulate the level of cyclin-dependent kinases CDK2, CDK4, and CDK6. The data presented indicate that deregulation of RPS5 gene expression (constitutive expression) affects RPS5 protein level and delays both the onset of initiation of erythroid maturation and entrance in cell cycle arrest in inducer-treated MEL cells.
现有证据表明，一些核糖体蛋白除了作为核糖体亚基的结构成分外，还参与细胞分化和凋亡的调控。正如我们之前所表明的，小鼠红白血病（MEL）细胞的红细胞分化起始与编码核糖体RNA、核糖体蛋白S5（RPS5）和L35a的基因的转录失活有关。在本研究中，我们扩展了这些观察结果，并研究了用RPS5 cDNA转染MEL细胞是否会影响红细胞成熟起始的发生及其进入细胞周期停滞状态。建立了稳定转染的MEL克隆细胞（MEL-C14和MEL-C56），并评估了它们产生RPS5 RNA转录本及其翻译产物的能力。RPS5 cDNA转染对诱导转染的MEL细胞中RPS5基因表达模式和RPS5蛋白积累的影响与它们的以下能力相关：（a）启动分化，（b）在G(1)/G(0)期进入细胞周期停滞，以及（c）调节细胞周期蛋白依赖性激酶CDK2、CDK4和CDK6的水平。所呈现的数据表明，RPS5基因表达失调（组成型表达）会影响RPS5蛋白水平，并延迟诱导剂处理的MEL细胞中红细胞成熟起始的发生和进入细胞周期停滞。
