Functions of a novel, testis-specific SMC protein

在四种真核细胞结构维持染色体(SMC)蛋白中，酵母SMC1和SMC3蛋白是有丝分裂和减数分裂姐妹染色单体凝聚和DNA重组所必需的。对哺乳动物SMC蛋白在减数分裂中的作用知之甚少，也没有细胞或组织特异性SMC蛋白变体的报道。本提案侧重于对我们发现的一种新的、减数分裂特异的SMC蛋白进行细胞、分子和组织学分析，命名为SMC1beta。SMC1beta与体细胞SMC1同源，被认为是减数分裂特有的异构体。我们认为SMC1beta在哺乳动物减数分裂过程中起着重要作用。这一作用应该发生在减数分裂姐妹染色单体的聚集和DNA重组中，并且应该需要与其他减数分裂蛋白相互作用，以及减数分裂特有的蛋白质-DNA结构。我们的目的是确定SMC1beta在精子发生中表达的发育阶段特异性，鉴定和鉴定与SMC1beta特异相互作用的蛋白质，并破译SMC1beta与减数分裂染色质的相互作用。有迹象表明存在一个新的SMC1beta/SMC3复合体，以及SMC1beta在减数分裂前期和后期的功能。SMC1beta的体内功能将通过在小鼠中删除该基因来研究。我们期望在这些动物中有减数分裂特有的表型。SMC1beta的一个显著特征是一个基本的C-末端28个氨基酸序列。我们预测，这个独特的C-末端基序有助于蛋白质特定的分子和细胞特征，我们将对此进行分析。我们的工作还将建立细胞类型特定的SMC蛋白变体的新概念。由于我们认为SMC1beta是哺乳动物减数分裂的关键蛋白，我们的结果不仅对于更好地理解哺乳动物SMC蛋白生物学，而且对于理解减数分裂染色质和DNA动力学，从而对人类生殖生物学和健康都具有重要意义。

Of the four eukaryotic structural maintenance of chromosomes (SMC) proteins, the yeast SMC1 and SMC3 proteins were recently shown to be required for mitotic and meiotic sister chromatid cohesion and DNA recombination. Very little is known on the role of mammalian SMC proteins in meiosis, and no cell- or tissue-specific variant of SMC proteins has been reported. This proposal focuses on the cellular, molecular, and organismal analysis of a novel, meiosis-specific SMC protein identified by us, named SMC1beta. SMC1beta is homologous to somatic SMC1 and considered a meiosis-specific isoform. We propose that SMC1beta plays an essential role in mammalian meiosis. This role should be in meiotic sister chromatid cohesion and DNA recombination, and should require interactions with other meiotic proteins, and meiosis-specific protein-DNA structures. Our aim is to determine the developmental stage-specificity of SMC1beta expression in spermatogenesis, to identify and characterize proteins that specifically interact with SMC1beta and to decipher the interaction of SMC1beta with meiotic chromatin. Indications exist for a novel SMC1beta/SMC3 complex, and for a function of SMC1beta in prophase I and in later stages of meiosis. The in vivo function of SMC1beta will be studied by deleting the gene in mice. We expect a meiosis-specific phenotype in the animals. A prominent feature of SMC1beta is a basic C-terminal 28 amino acids sequence. We predict that this unique C-terminal motif contributes to the protein specific molecular and cellular features, which we will analyze. Our work will also establish the novel concept of cell-type specific SMC protein variants. Since we consider SMC1beta a key protein for mammalian meiosis, our results will be important not only for better understanding mammalian SMC protein biology, but also for understanding meiotic chromatin and DNA dynamics, and thus for human reproductive biology and health.