Molecular Characterization of the HRP1/DSE Complex

信使（mRNA）降解是一个在基因表达调控中起重要作用的过程，mRNA降解速率变化很大，并且可以响应于环境信号而被调节。 许多研究表明，mRNA周转与翻译有关。无义介导的mRNA衰变途径是一种已被广泛研究并明确证实翻译和mRNA周转之间联系的途径。在原核生物和真核生物中，基因中的无义突变可以加速从该基因转录的mRNA的衰变。先前的结果已经证明，除了无义密码子之外，位于终止密码子3'的下游序列元件（DSE）是促进无义介导的mRNA降解所必需的。此外，UPF 1、UPF 2和UPF 3中的突变导致含无义mRNAS的积累增加，而对大多数野生型转录物的丰度没有影响。最近，我们已经确定了HRP 1，作为一个反式作用因子参与这一途径。基于这些研究，我们概述了 鉴定和表征参与调节NMD途径活性的几种顺式作用元件和反式作用因子。我们的主要研究目标是进一步表征NMD途径。基于我们的研究结果，我们将表征促进无义介导的mRNA衰变所需的下游序列元件。我们将继续在分子和生物化学水平上表征HRP 1/DSE复合物在无义介导的mRNA衰变途径中的作用。 我们还将集中于识别和表征的反式作用因子参与 与HRPI相关的无义介导的mRNA衰变途径。酿酒酵母 酿酒酵母将被用作我们的模型系统来理解这个过程。借助分子生物学、遗传学和生物化学的方法，我们希望对这些因子如何参与核质转运、mRNA周转和翻译有更多的了解。

Messenger (mRNA) degradation is a process that plays an important role in the regulation of gene expression, mRNA decay rates vary greatly and can be modulated in response to environmental signals. Many studies have demonstrated that mRNA turnover can be linked to translation. One pathway that has been extensively studied and clearly exemplifies the link between translation and mRNA turnover is the nonsense-mediated mRNA decay pathway. In both prokaryotes and eukaryotes, nonsense mutations in a gene can accelerate the decay of the mRNA transcribed from that gene. Previous results have demonstrated that, in addition to a nonsense-codon, downstream sequence elements (DSE) located 3' from the stop codon are required to promote nonsense-mediated mRNA decay. Further, mutations in UPF1, UPF2, and UPF3 result in an increased accumulation of nonsense-containing mRNAS while having no effect on the abundance of most wild-type transcripts. More recently, we have identified HRP1, as a trans-acting factor involved in this pathway. Based on these studies, we have outlined the identification and characterization of several cis-acting elements and trans-acting factors involved in modulating the activity of the NMD pathway. Our main research goal is to further characterize the NMD pathway. Based on our results, we will characterize the downstream sequence elements required for promoting nonsense-mediated mRNA decay. We will continue to characterize at both the molecular and biochemical levels the role of the HRP1/DSE complex in the nonsense-mediated mRNA decay pathway. We will also focus on the identification and characterization of trans-acting factors involved in nonsense-mediated mRNA decay pathway that are related to HRPI. The yeast Saccharomyces cerevisiae will be used as our model system to understand this process. With the aid of molecular, genetic and biochemical approaches, we intend to gain more understanding on how these factors are involved in nucleocytoplasmic transport, mRNA turnover and translation.