Cunningham K S, Hanson M N, Schoenberg D R
Department of Molecular and Cellular Biochemistry and Comprehensive Cancer Center, Ohio State Biochemistry Program and Molecular, Cellular and Developmental Biology Program, The Ohio State University, Columbus, OH 43210, USA.
Nucleic Acids Res. 2001 Mar 1;29(5):1156-62. doi: 10.1093/nar/29.5.1156.
Estrogen induces a global change in the translation profile of Xenopus hepatocytes, replacing serum protein synthesis with production of the yolk protein precursor vitellogenin. This is accomplished by the coordinate destabilization of serum protein mRNAs and the transcriptional induction and subsequent stabilization of vitellogenin mRNA. Previous work identified an endonuclease activity whose appearance on polysomes correlated with the disappearance of serum protein mRNAs. This enzyme, polysomal ribonuclease 1 (PMR1), is a novel member of the peroxidase gene family. The current study examined the association of PMR1 with its mRNA targets on polysomes and mRNPs. The highest amount of polysome-bound PMR1 was observed prior to estrogen induction of mRNA decay. Its distribution on sucrose density gradients matched the absorbance profile of polysome-bound mRNA, suggesting that PMR1 forms a latent complex with mRNA. Following dissociation with EDTA the 62 kDa PMR1 sedimented with a larger complex of >670 kDa. Estrogen induces a 22-fold increase in unit enzymatic activity of polysome-bound PMR1, and a time-dependent loss of PMR1 from polysomes in a manner that mirrors the disappearance of albumin mRNA. These data suggest that the key step in the extensive estrogen-induced change in mRNA decay in Xenopus liver is activation of a latent mRNA endonuclease associated with its target mRNA.
雌激素可诱导非洲爪蟾肝细胞的翻译谱发生全局性变化，使卵黄蛋白原（一种卵黄蛋白前体）的生成取代血清蛋白的合成。这是通过血清蛋白mRNA的协同去稳定作用以及卵黄蛋白原mRNA的转录诱导和随后的稳定化来实现的。先前的研究发现了一种核酸内切酶活性，其在多核糖体上的出现与血清蛋白mRNA的消失相关。这种酶，即多核糖体核糖核酸酶1（PMR1），是过氧化物酶基因家族的一个新成员。当前的研究检测了PMR1与其在多核糖体和mRNA-蛋白质复合物上的mRNA靶标的关联。在雌激素诱导mRNA降解之前，观察到与多核糖体结合的PMR1量最高。其在蔗糖密度梯度上的分布与多核糖体结合的mRNA的吸光度谱相匹配，表明PMR1与mRNA形成了一种潜在复合物。用EDTA解离后，62 kDa的PMR1与一个大于670 kDa的更大复合物一起沉降。雌激素可使与多核糖体结合的PMR1的单位酶活性增加22倍，并使PMR1以反映白蛋白mRNA消失的方式随时间从多核糖体上丢失。这些数据表明，非洲爪蟾肝脏中雌激素广泛诱导的mRNA降解变化的关键步骤是与靶mRNA相关的潜在mRNA核酸内切酶的激活。
