Padgett R A, Wahl G M, Coleman P F, Stark G R
J Biol Chem. 1979 Feb 10;254(3):974-80.
We have investigated the mechanism of overproduction of the multifunctional protein catalyzing the first three steps of UMP biosynthesis in stable mutants of Syrian hamster cells in culture. The rate of degradation of this protein is unaltered in one mutant cell line which overproduces it by 118-fold. In all mutants tested, the increase in the rate of synthesis of this protein is equal to the increase in its steady state concentration. There is a similar correlation between steady state levels of this protein in vivo and the capacity of polysomal RNA isolated from these cells to direct the synthesis of the protein in vitro. The one mutant cell line studied contains large amounts of a polysomal poly(A)-containing RNA (Mr = 2.7 +/- 0.2 times 10(6)) that is not detected in wild type cells. This large RNA co-sediments in sucrose gradients with the capacity to direct the synthesis of the multifunctional protein in vitro.
我们研究了在培养的叙利亚仓鼠细胞稳定突变体中，催化尿苷一磷酸（UMP）生物合成前三步的多功能蛋白质过量产生的机制。在一个将该蛋白质过量产生118倍的突变细胞系中，这种蛋白质的降解速率未发生改变。在所有测试的突变体中，这种蛋白质合成速率的增加与其稳态浓度的增加相等。在体内这种蛋白质的稳态水平与从这些细胞中分离的多聚核糖体RNA在体外指导该蛋白质合成的能力之间，存在类似的相关性。所研究的一个突变细胞系含有大量多聚核糖体的含聚腺苷酸（poly(A)）RNA（分子量=2.7±0.2×10⁶），而在野生型细胞中未检测到这种RNA。这种大的RNA在蔗糖梯度中共沉降，具有在体外指导多功能蛋白质合成的能力。
