基因表达的精确调控是细胞行使正常功能、快速响应外界环境变化的一个重要保证。包括泛素化修饰在内的蛋白质翻译后修饰是一种可通过调节特定因子功能及时空状态而实现对基因表达进行准确调控的有效方式。丝状真菌瑞氏木霉具有在纤维素存在条件下快速合成大量纤维素酶的重要生物学特性，但其转录调控分子机制的许多精细环节并不清楚。本项申请拟围绕前期工作中鉴定到的在纤维素酶基因表达调控中发挥重要作用的泛素结合酶TrUBC，系统研究其介导的泛素化修饰在纤维素酶基因转录调控中的作用机制，包括揭示TrUBC在纤维素酶基因表达调控中的动态作用模式，筛选鉴定与TrUBC偶联的泛素连接酶E3及泛素化修饰的靶点因子，解析靶点因子发生的泛素化修饰模式及该修饰模式对纤维素酶基因转录表达的调控机制。研究结果将不仅有助于全面深化对瑞氏木霉纤维素酶调控体系的认识，还将拓展蛋白翻译后修饰在真核基因表达调控中的作用研究。

Precise control of gene expression is key for cells to carry out various processes as well as to rapidly respond to even subtle environmental changes. One of the efficient ways to fine-tune the expression of a specific gene is to dynamically modulate the function as well as the temporal-spatial status of regulators through post-translational modifications including ubiquitylation. Filamentous fungi Trichoderma reesei is characterized by its outstanding ability to rapidly initiate the launching of cellulase biosynthesis in the presence of cellulose substrates which otherwise are kept silent. Unfortunately, many facets of the precise mechanism involved in the transcription regulation is not clear yet. The present application aims to focus on our recently identified ubiquitin-conjugating enzyme TrUBC, which was shown to play an important role in the induced cellulase gene expression. Systematic studies will be carried out to elucidate the mechanism by which the TrUBC-mediated ubiquitylation participates in the regulation of cellulase gene expression. Attempts made will include the revelation of the dynamic behavior of TrUBC during the induced expression of cellulases, the screening and identification of the coupled ubiquitin ligase E3 as well as the finally modified regulator(s). No efforts will then be spared to thoroughly dissect the mode of ubiquitylation occurring on the substrate including the modification sites, the type of linkage of ubiquitin chains attached to targeted substrates. The effect of the changes in the ubiquitylating machinery and in the modification mode on the final induced expression of cellulase genes will be simultaneously analyzed. The results are anticipated not only to provide deeper insights into the regulation system for T. reesei cellulases, but also to extend the mechanistic understanding on the role of post-translational protein modification in eukaryotic gene regualtion.