Bustelo X R, Otero A, Gómez-Márquez J, Freire M
Departamento de Bioquímica e Bioloxía Molecular, Facultade de Bioloxía, Universidade de Santiago, Galicia, Spain.
J Biol Chem. 1991 Jan 25;266(3):1443-7.
Prothymosin alpha (ProT alpha) is a widely distributed acidic protein whose function has been related to cell proliferation. We have analyzed the expression of the rat ProT alpha gene in several proliferative systems: concanavalin A (ConA)/interleukin-2-stimulated thymocytes, ConA-stimulated splenic T-lymphocytes, and hepatocytes proliferating during liver regeneration. In these systems, ProT alpha mRNA was detected in all stages of the cell cycle, with maximal increments (2-4-fold) at the beginning of the S phase. By contrast, the mRNAs for proliferating cell nuclear antigen/cyclin and histone H3, two cell-cycle-regulated proteins, were hardly detected in resting cells but increased notably at the G1/S boundary and in the S phase, respectively. Treatment of T-cells with the calcium ionophore A23187 increased ProT alpha mRNA levels 2.5-fold, whereas phorbol 12-myristate 13-acetate, a protein kinase C activator, had no effect on ProT alpha gene expression. Incubation of ConA-stimulated T-cells with hydroxyurea, a DNA synthesis inhibitor, did not decrease the levels of ProT alpha mRNA, indicating that its expression is independent of DNA synthesis. These findings suggest that ProT alpha is required throughout all the stages of the cell cycle, resembling a constitutively expressed gene rather than one strictly involved in cell proliferation.
前胸腺素α（ProTα）是一种广泛分布的酸性蛋白，其功能与细胞增殖有关。我们分析了大鼠ProTα基因在几种增殖系统中的表达：伴刀豆球蛋白A（ConA）/白细胞介素-2刺激的胸腺细胞、ConA刺激的脾T淋巴细胞以及肝再生过程中增殖的肝细胞。在这些系统中，细胞周期的所有阶段均检测到ProTα mRNA，在S期开始时增幅最大（2至4倍）。相比之下，增殖细胞核抗原/细胞周期蛋白和组蛋白H3这两种细胞周期调节蛋白的mRNA在静止细胞中几乎检测不到，但分别在G1/S边界和S期显著增加。用钙离子载体A23187处理T细胞可使ProTα mRNA水平提高2.5倍，而蛋白激酶C激活剂佛波酯12-肉豆蔻酸酯13-乙酸酯对ProTα基因表达没有影响。用DNA合成抑制剂羟基脲孵育ConA刺激的T细胞不会降低ProTα mRNA水平，表明其表达与DNA合成无关。这些发现表明，ProTα在细胞周期的所有阶段都是必需的，类似于一个组成性表达的基因，而不是一个严格参与细胞增殖的基因。
