Brewer G, Ross J
McArdle Laboratory for Cancer Research, University of Wisconsin, Madison 53706.
Mol Cell Biol. 1989 May;9(5):1996-2006. doi: 10.1128/mcb.9.5.1996-2006.1989.
The turnover rates of some mRNAs vary by an order of magnitude or more when cells change their growth pattern or differentiate. To identify regulatory factors that might be responsible for this variability, we investigated how cytosolic fractions affect mRNA decay in an in vitro system. A 130,000 X g supernatant (S130) from the cytosol of exponentially growing erythroleukemia cells contains a destabilizer that accelerates the decay of polysome-bound c-myc mRNA by eightfold or more compared with reactions lacking S130. The destabilizer is deficient in or absent from the S130 of cycloheximide-treated cells, indicating that it is labile or is repressed when translation is blocked. It is not a generic RNase, because it does not affect the turnover of delta-globin, gamma-globin, or histone mRNA and does not destabilize a major portion of polysomal polyadenylated mRNA. The destabilizer accelerates the turnover of the c-myc mRNA 3' region, as well as subsequent 3'-to-5' degradation of the mRNA body. It is inactivated in vitro by mild heating and by micrococcal nuclease, suggesting that it contains a nucleic acid component. c-myb mRNA is also destabilized in S130-supplemented in vitro reactions. These results imply that the stability of some mRNAs is regulated by cytosolic factors that are not associated with polysomes.
当细胞改变其生长模式或分化时，一些mRNA的周转率会相差一个数量级或更多。为了确定可能导致这种变异性的调节因子，我们研究了胞质组分在体外系统中如何影响mRNA降解。来自指数生长的红白血病细胞胞质的130,000×g上清液（S130）含有一种去稳定剂，与缺乏S130的反应相比，它能使多核糖体结合的c-myc mRNA的降解加速八倍或更多。在环己酰亚胺处理的细胞的S130中，该去稳定剂缺乏或不存在，这表明当翻译被阻断时它是不稳定的或被抑制的。它不是一种通用的核糖核酸酶，因为它不影响δ-珠蛋白、γ-珠蛋白或组蛋白mRNA的周转，也不会使大部分多核糖体多聚腺苷酸化mRNA不稳定。该去稳定剂加速c-myc mRNA 3'区域的周转以及随后mRNA主体从3'到5'的降解。它在体外通过温和加热和微球菌核酸酶失活，这表明它含有核酸成分。在补充了S130的体外反应中，c-myb mRNA也会变得不稳定。这些结果表明，一些mRNA的稳定性受与多核糖体无关的胞质因子调节。
