俄亥俄大學的科學家進行的新研究顯示,，會破壞某些蛋白質之信使RNA (mRNA)的酵素PMR1,，在細胞受到環(huán)境壓力期間，保護mRNA,。這種反應會使癌細胞在化療和放射治療中存活下來,。
這種酵素會依附在某些mRNA分子正，并且遺留了一顆插著保險拴的手榴彈,。這些mRNAs傳遞著制造某些特殊蛋白質的信息,，當命令到達時，細胞必須停止手邊的工作來制造這些蛋白質,。但是當制造的指令抵達時,，同時也將手榴彈的保險拴拉開，使酵素開始破壞mRNA,，因此迅速地抑制這種蛋白質的生產,。
這項新研究發(fā)現(xiàn)，在面臨這種環(huán)境壓力的情況下,，這種依附在mRNA上的酵素PMR1,，也會幫助mRNA在細胞中搭建臨時的遮雨棚，又稱為壓力顆粒(stress granules),，mRNA可以在壓力顆粒中受到保護,，使環(huán)境壓力結束后，蛋白質的生產可以迅速地恢復,。
壓力顆粒是mRNA 和蛋白質短暫的聚集處,，當細胞面臨不利的環(huán)境條件如饑餓、氧氣過低或接受化療或放射治療時,，mRNA 和蛋白質就會暫避于壓力顆粒中,。
這項研究結果發(fā)表于12月號的Molecular and Cellular Biology中，研究作者是俄亥俄州立大學的Daniel R. Schoenberg教授,。藉由了解PMR1和類似的酵素如何產生壓力顆粒,，研究人員將可以學習如何抑制癌細胞的防護機制,，并使癌細胞無法對抗癌癥治療。
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.
