POST-TRANSLATIONAL PROTEIN MODIFICATION AND RNA PROCESSING AND DECAY

这个子项目是利用资源的许多研究子项目之一。 由NIH/NCRR资助的中心拨款提供。对子项目的主要支持 子项目的首席调查员可能是由其他来源提供的， 包括美国国立卫生研究院的其他来源。为子项目列出的总成本可能 表示该子项目使用的中心基础设施的估计数量， 不是由NCRR赠款提供给次级项目或次级项目工作人员的直接资金。 MRNA帽和相扑蛋白修饰的结构研究。信使核糖核酸封顶。在所有真核生物中，需要三个催化步骤才能正确地封顶新生的mRNA链。该基因的5‘-三磷酸(Pppn)被RNA三磷酸酶切割，生成5’-二磷酸(PPN)的mRNA分子。该反应的产物是RNA鸟苷酸转移酶的底物，该反应将GMP从GTP转移到产生GpppN的RNA的5‘二磷酸末端。然后，鸟苷帽被RNA(鸟嘌呤-7)甲基转移酶甲基化，形成功能性m7GpppN结构。每一种帽子形成活动对萌芽酵母的细胞生长都是必不可少的。我们正在表征这些酶中的几种的结构基础，它们彼此复合，与各种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。已知的是，小的泛素样修饰物SUMO调节真核生物的核运输、应激反应和信号转导，这是酵母细胞周期进展所必需的过程。与泛素修饰类似，相扑结合发生在赖氨酸残基上，并由相扑激活酶E1、相扑结合酶E2、相扑结合酶、E3样结合辅因子以及催化相扑加工和去共轭的蛋白酶催化。相扑修饰似乎并不针对降解的蛋白质，而是通过改变细胞定位、生化激活或通过保护泛素依赖的降解来改变目标蛋白质的功能。我们已经从结构上描述了这个系统的几个组成部分，既有单独的，也有相互复杂的。我们目前正在表征E1、E2、E3、相扑与各种底物和辅因子之间额外络合物的结构基础。

This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. Primary support for the subproject and the subproject's principal investigator may have been provided by other sources, including other NIH sources. The Total Cost listed for the subproject likely represents the estimated amount of Center infrastructure utilized by the subproject, not direct funding provided by the NCRR grant to the subproject or subproject staff. Structural studies of mRNA capping & SUMO protein modification. mRNA capping. Three catalytic steps are required in all eukaryotic organisms to properly cap the nascent mRNA chain. The 5' triphosphate (pppN) of the mRNA is cleaved by RNA triphosphatase at the ¿ position to produce a 5' diphosphate (ppN) mRNA molecule. The product of this reaction is substrate for RNA guanylyltransferase in a reaction that transfers GMP from GTP to the 5' diphosphate end of the RNA producing GpppN. The cap guanylate is then methylated by RNA (guanine-7) methyltransferase to form the functional m7GpppN structure. Each of the cap- forming activities is essential for cell growth in budding yeast. We are characterizing the structural basis for several of these enzymes in complex with each other, in complex with various RNA and oligonucleotide compounds, and in complex with the phosphorylated CTD from RNA polymerase II. SUMO. The small ubiquitin-like modifier SUMO is known to regulate 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.