Molecular Characterization of the HRP1/DSE Complex

信使(Messenger，mRNA)降解是一个在基因表达调控中起重要作用的过程，其衰减速率变化很大，可以根据环境信号的变化进行调节。 许多研究表明，信使核糖核酸的周转与翻译有关。一条已经被广泛研究并清楚地例证了翻译和信使核糖核酸转换之间的联系的途径是无义介导的信使核糖核酸衰变途径。在原核生物和真核生物中，一个基因的无义突变都会加速该基因转录的信使核糖核酸的衰退。先前的研究结果表明，除了无义密码子外，位于终止密码子3‘的下游序列元件(DSE)也是促进无义介导的mRNA衰变所必需的。此外，UPF1、UPF2和UPF3的突变导致含有无义的mRNAs的积累增加，而对大多数野生型转录本的丰度没有影响。最近，我们已经确定HRP1是参与这一途径的反式作用因子。根据这些研究，我们概述了 几种参与调节NMD途径活性的顺式作用元件和反式作用因子的鉴定和表征。我们的主要研究目标是进一步研究NMD的途径。基于我们的结果，我们将描述促进无义介导的mRNA衰变所需的下游序列元件。我们将继续在分子和生化水平上表征HRP1/DSE复合体在无意义介导的mRNA衰退途径中的作用。 我们还将着重于识别和表征涉及到的反式作用因素 与HRPI相关的无义介导的mRNA衰变途径。酵母菌 我们将以酿酒厂为模型系统来理解这一过程。借助于分子、遗传学和生物化学方法，我们打算更多地了解这些因子是如何参与核质运输、信使核糖核酸周转和翻译的。

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.