Biogenese des Proteasoms in Saccharomyces cerevisiae

在真核生物中，20S蛋白酶体是由两个类似于半蛋白酶体的预组装的前体复合体形成的。我们已经确定了在这些复合体中存在一种蛋白质Ump1p，它是酿酒酵母20S蛋白酶体正常成熟所必需的。我们将结合生物化学和遗传学的方法来详细研究这种前体复合体的组成和结构，以及导致其形成的Ump1p亚基之间相互作用的性质。除此之外，我们的主要目标是了解控制两个这样的前体组装20S蛋白酶体的过程，以及通过处理β-亚基形成活性位点的过程。一些观察表明，Ump1p与Pre2p的前肽(Beta5)之间的特异性相互作用在其从两个前体复合体组装时触发了蛋白酶体的激活。为了验证这一观点，我们已经开始确定这两个多肽中相互作用的结构域。我们最近的结果表明，与Ump1p相关的成熟因子显然存在于所有真核生物中。这些亲缘关系的比较为鉴定Ump1p组装成前体复合体和/或其在β亚基成熟中的功能至关重要的序列或结构元件提供了重要的指导。

In eukaryotes, 20S proteasomes are formed from two preassembled precursor complexes that closely resemble half-proteasomes. We have identified a protein, Ump1p, that is present in these complexes, and that is required for proper maturation of 20S proteasomes in S.cerevisiae.We will use a combination of biochemical and genetic approaches to study, in detail, the composition and structure of such precursor complexes, and the nature of interactions between its subunits and Ump1p that lead to its formation. Above that, our prime goal is to understand the processes that control the assembly of 20S proteasome from two such precursors and the formation of active sites through processing of beta-subunits. Several observations indicate that a specific interaction between Ump1p and the propeptide of Pre2p (beta5) triggers the proteasome activation upon its assembly from two precursor complexes. To test this idea we have begun to determine the domains in these two polypeptides whose interactions are underlying this process.Our recent results show that maturation factors related to Ump1p apparently exist in all eukaryotes. A comparison of these relatives has provided important guides to the identification of sequence or structure elements critical to assembly of Ump1p into precursor complexes and/or its function in beta subunit maturation.