Structure and Function of hnRNP Proteins

在20多种hnRNP蛋白的复合体中，发现了9514179个威廉姆斯异质性核RNA(HnRNA)。A1 hnRNP的不同寻常之处在于，除了在hnRNP纤维形成中的结构作用外，它似乎还有几个功能。A1与中间丝相互作用；调节替代的5‘-剪接；可以识别类似于剪接位点共识序列的高亲和力RNA靶序列；并促进互补核酸的退火。后者的“活性”是由A1中关键丝氨酸残基的磷酸化控制的。A1 hnRNP在其NH2末端也含有两个保守的RNA结合域，并具有一个RGG重复序列，这可能是一个重要的RNA结合域。在这些研究中，酵母双杂交系统将被用于识别体内与A1相互作用的其他蛋白质。将使用圆二色谱、荧光光谱和核磁共振来探索RGG基序的结构和核酸结合特性，并定位结构域中的甲基化位置。进行RGG翻译后修饰的甲基酶将被克隆和分析。这些研究的结果将显著增加我们对多功能hnRNP蛋白的理解，hnRNP蛋白在前mRNA生物发生中发挥关键作用。虽然细胞内包含的所有信息都是在DNA中编码的，但细胞及其组成的器官和系统的大部分实际功能是由蛋白质执行的，而蛋白质又由不同的氨基酸序列组成。由于蛋白质是在细胞的细胞质中制造的，而编码蛋白质的DNA在细胞核中，因此一种被称为信使RNA(信使RNA)的分子在结构上与DNA有关，用于将蛋白质合成的“信息”从细胞核传输到细胞质。一般来说，每种蛋白质都有一个独特的信使核糖核酸。该项目旨在了解一类对信使核糖核酸的形成和运输至关重要的核蛋白(hnRNP蛋白)如何发挥其功能。特别是，将研究hnRNP蛋白质如何与mRNA和其他蛋白质结合，以便更好地了解基因表达的这一关键步骤。***

9514179 Williams Heterogeneous nuclear RNAs (hnRNA) are found in the nucleus in complexes with more than 20 hnRNP proteins. A1 hnRNP is unusual in that it appears to have several functions in addition to its structural role in hnRNP fiber formation. A1 interacts with intermediate filaments; modulates alternative 5'-splicing; can recognize a high affinity RNA target sequence that is similar to splice site consensus sequences; and facilitates annealing of complementary nucleic acids. The latter "activity" is controlled by phosphorylation of a critical serine residue in A1. A1 hnRNP also contains two conserved RNA binding domains at its NH2 terminus, and has an RGG repeat which may be a significant RNA binding domain. In these studies, the yeast two hybrid system will be used to identify other proteins that interact with A1 in vivo. Circular dichroism, fluorescence spectroscopy, and nuclear magnetic resonance will be used to probe the structure and nucleic acid binding properties of the RGG motif, and to locate sites of methylation within the domain. The methylase that carries out the posttranslational modification of the RGG will be cloned and analyzed. The results of these studies will significantly increase our understanding of a multi-functional hnRNP protein that plays a key role in pre-mRNA biogenesis. %%% Although all of the information contained within a cell is encoded in its DNA, most of the actual functions of cells and the organs and systems that they make up are carried out by proteins that are in turn composed of varying sequences of amino acids. Since proteins are made in the cytoplasm of the cell while the DNA that encodes them is in the nucleus, a molecule called messenger RNA (mRNA), structurally related to DNA, serves to transport the "message" for protein synthesis from the nucleus to the cytoplasm. In general, there is a unique mRNA for each protein. This project is directed at understanding how a particular class of nuclear proteins (hnRNP proteins) that are cri tical for the formation and transport of mRNA carry out their functions. In particular, how hnRNP proteins bind to mRNA and to other proteins will be investigated so that this critical step in gene expression will be better understood. ***