俄亥俄大学的科学家进行的新研究显示，会破坏某些蛋白质之信使RNA (mRNA)的酵素PMR1，在细胞受到环境压力期间，保护mRNA。这种反应会使癌细胞在化疗和放射治疗中存活下来。
这种酵素会依附在某些mRNA分子正，并且遗留了一颗插着保险拴的手榴弹。这些mRNAs传递着制造某些特殊蛋白质的信息，当命令到达时，细胞必须停止手边的工作来制造这些蛋白质。但是当制造的指令抵达时，同时也将手榴弹的保险拴拉开，使酵素开始破坏mRNA，因此迅速地抑制这种蛋白质的生产。
这项新研究发现，在面临这种环境压力的情况下，这种依附在mRNA上的酵素PMR1，也会帮助mRNA在细胞中搭建临时的遮雨棚，又称为压力颗粒(stress granules)，mRNA可以在压力颗粒中受到保护，使环境压力结束后，蛋白质的生产可以迅速地恢复。
压力颗粒是mRNA 和蛋白质短暂的聚集处，当细胞面临不利的环境条件如饥饿、氧气过低或接受化疗或放射治疗时，mRNA 和蛋白质就会暂避于压力颗粒中。
这项研究结果发表于12月号的Molecular and Cellular Biology中，研究作者是俄亥俄州立大学的Daniel R. Schoenberg教授。藉由了解PMR1和类似的酵素如何产生压力颗粒，研究人员将可以学习如何抑制癌细胞的防护机制，并使癌细胞无法对抗癌症治疗。
部分英文原文：
Polysome-Bound Endonuclease PMR1 Is Targeted to Stress Granules via Stress-Specific Binding to TIA-1
The generalized process of mRNA decay involves deadenylation followed by release from translating polysomes, decapping, and exonuclease decay of the mRNA body. In contrast the mRNA endonuclease PMR1 forms a selective complex with its translating substrate mRNA, where it initiates decay by cleaving within the mRNA body. In stressed cells the phosphorylation of the subunit of eukaryotic initiation factor 2 causes translating mRNAs to accumulate with stalled 48S subunits in large subcellular structures termed stress granules (SGs), wherein mRNAs undergo sorting for reinitiation, storage, or decay. Given the unique relationship between translation and PMR1-mediated mRNA decay, we examined the impact of stress-induced dissociation of polysomes on this process. Arsenite stress disrupts the polysome binding of PMR1 and its substrate mRNA but has no impact on the critical tyrosine phosphorylation of PMR1, its association with substrate mRNA, or its association with the functional 680-kDa mRNP complex in which it normally resides on polysomes. We show that arsenite stress drives PMR1 into an RNase-resistant complex with TIA-1, and we identify a distinct domain in the N terminus of PMR1 that facilitates its interaction with TIA-1. Finally, we show that arsenite promotes the delayed association of PMR1 with SGs under conditions which cause tristetraprolin and butyrate response factor 1, proteins that facilitate exonucleolytic mRNA, to exit SGs.
