课题组前期通过肌肉蛋白组学分析发现MSTN-/-牛和野生型牛中两个重要的泛素蛋白水解系统的酶PSMB5和UCH-L3的表达存在显著性差异，结合在牛肌卫星细胞上的初步验证，推测泛素化途径对牛肌肉发育产生了重要的调控作用。本研究在前期研究基础上，对MSTN-/-牛和野生型牛进行肌肉泛素化蛋白组学分析，筛选泛素化修饰差异蛋白，寻找MSTN、PSMB5和UCH-L3可能调控的泛素化蛋白网络，解析MSTN通过泛素化途径调控肌肉发育的可能通路，然后利用牛骨骼肌卫星细胞成肌分化模型，对MSTN、PSMB5和UCH-L3以及它们调控的关键泛素化蛋白在牛成肌分化过程中的作用和机制进行研究，找到其参与的具体信号通路并对成肌分化关键泛素化调控蛋白进行初步的体内功能验证，综合分析泛素化途径对牛肌肉发育分化的调控作用机制，为肌肉发育分化的泛素化研究提供参考，为肉牛的分子育种研究提供有用的靶标基因。

Ubiquitination is a key post-translational modification and plays an important role in many biological processes. In our previous study, muscle proteomic analysis of MSTN-/- cattle and wild-type cattle was conducted, and two important ubiquitinating regulatory enzymes PSMB5 (Proteasome subunit beta type-5) and UCH-L3 (Ubiquitin carboxyl-terminal hydrolase isozyme L3) were found significantly differentially expressed between MSTN-/- cattle and wild-type cattle. Our preliminary study reviewed that MSTN, PSMB5 and UCH-L3 were differentially expressed in bovine skeletal muscle satellite cells myogenic differentiation process. These data indicated ubiquitination process may play a key role in bovine muscle development. However, the role of ubiquitination process in muscle development still need well investigated. In this study, anti-ubiquitination-based enrichment and liquid chromatography-tandem mass spectrometry will be applied to comprehensively investigate the global ubiquitome in MSTN-/- cattle and wild-type cattle, select and validate the differential ubiquitinated proteins. Using bioinformatics analyses, construct interaction networks between ubiquitinated proteins and MSTN、PSMB5 and UCH-L3, analyze the possible muscle hypertrophy pathway of ubiquitination process induced by MSTN. Then the bovine skeletal muscle satellite cells induced myogenic differentiation model will be used to investigate the function and regulating mechanism of MSTN, PSMB5, UCH-L3 and their target key ubiquitinated proteins in bovine myogenic differentiation process, identify the signaling pathways of these key ubiquitinated proteins are involved, and detect the in vivo effects of the identified key ubiquitinated proteins in muscle atrophy or injury model. Through these methods, analyze the regulatory networks of ubiquitination process in bovine muscle development, and reveal the molecular mechanism of ubiquitination process in myogenic differentiation process. The results of this study could provide theoretical support for further research of ubiquitination process in bovine muscle development, and identify new target genes for the beef cattle breeding.