Characterization of messenger ribonucleoproteincomplexes (mRNPs) during cellular stresses

细胞暴露于各种形式的环境压力，如热或化学变化，导致常规基因的基因表达减少，而应激蛋白（热休克蛋白）的有利表达。我们最近的研究结果发现，酿酒酵母mRNA结合蛋白和mRNA输出因子Npl3p在应激过程中与mRNA分离，使其无法输出。目前尚不清楚这种解离是如何开始的。我们希望确定导致这种效应的信号级联，并研究Npl3p蛋白修饰是否可能导致解离，或者蛋白质与蛋白质的相互作用是否触发了mRNA/蛋白质复合物的重排。我们最近的研究结果已经确定Gbp2p和Hrb1p是npl3p同源的mRNA结合和穿梭蛋白。我们将分析它们在细胞应激时的行为，并将其与Npl3p进行比较。我们未发表的研究结果已经揭示了差异。应激时，Npl3p和Gbp2p的表达水平保持不变，而hrb1p的表达显著增加，表明对这种rna结合蛋白的需求增加。由于Npl3p不参与热休克mRNA的输出，正如我们之前所展示的，我们将讨论哪些mRNA输出因子介导这一过程。最后，我们的目标是在热休克mrna中找到那些负责其选择性输出的rna序列。

Exposure of cells to various forms of environmental stresses, like thermal or chemical changes, lead to a reduced gene expression of regular genes and the favored expression of stress proteins (heat shock proteins). Our recent results have uncovered that the Saccharomyces cerevisiae mRNA binding protein and mRNA export factor Npl3p dissociates from the mRNA during stress and leaves it exportincompetent behind. It is currently unknown how this dissociation is initiated. We would like to identify the signal-cascade that is responsible for this effect and investigate if Npl3p protein modifications might lead to the dissociation or if rather protein protein interactions are the trigger for the rearrangement of the mRNA/protein complexes. Our recent results have identified Gbp2p and Hrb1p as Npl3p-homologoues mRNA binding and shuttling proteins. We will analyze their behavior during cellular stress and compare it to that of Npl3p. Our unpublished results have revealed already differences. While the expression level of both, Npl3p and Gbp2p remain constant during stress, Hrb1p-expression is significantly increased, indicating an augmented requirement for this RNA-binding protein. Since Npl3p is not involved in the export of the heat shock mRNAs as we have shown earlier, we will address, which mRNA export factors mediate that process. Finally, we aim to find those RNA-sequences within the heat shock mRNAs that are responsible for their selective export.