STRUCTURAL STUDIES OF MRNA METABOLISM & SUMO PROTEIN MODIFICATION

该子项目是利用NIH/NCRR资助的中心赠款提供的资源的许多研究子项目之一。子项目和研究者（PI）可能从另一个NIH来源获得主要资金，因此可以在其他CRISP条目中表示。所列机构为中心，不一定是研究者所在机构。mRNA的成熟和衰变。细胞mRNA的稳定性和寿命取决于前mRNA的加工和衰变途径。我们研究了与RNA加帽相关的早期加工事件，包括真核生物中为新生mRNA链加帽所需的催化步骤。mRNA的5 <$三磷酸（pppN）被RNA三磷酸酶切割，产生5 <$二磷酸（ppN）mRNA分子。该反应产物是RNA鸟苷酰转移酶的底物，该反应将GMP从GTP转移到RNA的5 ′二磷酸末端（GpppN）。鸟苷酸被RNA（鸟嘌呤-7）甲基转移酶甲基化以形成功能性m7 GpppN帽。每一种冠状形成活动对细胞生长都是必不可少的。我们正在表征几种酶相互复合、与RNA和寡核苷酸化合物复合以及与来自RNA聚合酶II的磷酸化CTD复合的结构基础。RNA衰变在RNA代谢中也起着重要作用，我们正在进行旨在阐明控制几种衰变途径的调控机制的研究。相扑。SUMO调节真核生物的核转运、应激反应和信号转导，这是酵母细胞周期进程中必不可少的过程。与泛素修饰类似，SUMO缀合发生在赖氨酸残基上，并由E1（SUMO活化酶）、E2（SUMO缀合酶）、E3样缀合辅因子和催化SUMO加工和解缀合的蛋白酶催化。SUMO修饰似乎并不靶向降解蛋白，而是通过细胞定位、生物化学活化或通过保护免受泛素依赖性降解来改变靶蛋白功能。我们已经在结构上描述了这个系统的几个组成部分，无论是单独的还是相互复杂的。我们目前正在表征E1，E2，E3，SUMO和各种底物和辅因子之间的其他复合物的结构基础。

This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. mRNA maturation and decay. The stability and lifetime of cellular mRNA depends on pre-mRNA processing and decay pathways. We study early processing events associated with RNA capping including the catalytic steps that are required in eukaryotic organisms to cap the nascent mRNA chain. The 5¿ triphosphate (pppN) of the mRNA is cleaved by RNA triphosphatase to produce a 5¿ diphosphate (ppN) mRNA molecule. This reaction product is a substrate for RNA guanylyltransferase in a reaction that transfers GMP from GTP to the 5¿ diphosphate end of the RNA (GpppN). The guanylate is methylated by RNA (guanine-7) methyltransferase to form the functional m7GpppN cap. Each of the cap-forming activities is essential for cell growth. We are characterizing the structural basis for several enzymes in complex with each other, in complex with RNA and oligonucleotide compounds, and in complex with phosphorylated CTD from RNA polymerase II. RNA decay also plays an important role in RNA metabolism, and we are engaged in studies aimed at elucidating regulatory mechanisms controlling several decay pathways. SUMO. The small ubiquitin-like modifier SUMO regulates nuclear transport, stress response, and signal transduction in eukaryotes, a process that is essential for cell cycle progression in yeast. Analogous to ubiquitin modification, SUMO conjugation occurs on lysine residues and is catalyzed by E1, the SUMO activating enzyme, E2, the SUMO conjugation enzyme, E3-like conjugation cofactors, and proteases that catalyze SUMO processing and deconjugation. SUMO modification does not appear to target proteins for degradation, but rather alters the target protein function through changes in cellular localization, biochemical activation, or through protection from ubiquitin-dependent degradation. We have structurally characterized several components of this system, both alone and in complex with each other. We are currently characterizing the structural basis for additional complexes between E1, E2, E3, SUMO and various substrates and cofactors.