四膜虫端粒酶活性调节蛋白的结构与功能研究

Telomerase is involved in the end-replication of linear chromesomes and thus is important for aging, tumorigenesis and stem cell renewal. Physiological function of telomerase requires a variety of telomere-binding proteins. Tetrahymena telomere-binding protein Teb1 is comprised of four OB-fold domains, N, A, B and C; it binds with telomeric-repeat DNA sequence specifically and is important for telomere repeat addition processivity (RAP). Reported biochemical assays and the holoenzyme structure at a resolution of 9.4 Å indicate that Teb1C may interact with telomerase essential N-terminal domain (TEN). Similarly, TEN also binds specifically with telomere ssDNA and is essential for telomerase activity and RAP. However, their mechanisms for this role remain unclear. Teb2 and Teb3, proteins recently identified as Teb1-binding proteins, likely stabilize association of Teb1 with telomerase. Based on our results, we have crystallized Teb1C-Teb2N-Teb3 (TEB) complex and assured the interaction between TEB and TEN. This provides strong basis for high-resolution structure resolvement of TEB complex and TEB-TEN complex and further mechanism study. More importantly, this will promote the study of telomerase activity regulation in high organisms.

端粒酶参与线性染色体的末端复制，在衰老、癌症发生和干细胞更新中发挥着重要作用，但它生理功能的发挥还依赖其它端粒结合蛋白。四膜虫的端粒结合蛋白Teb1，由N、A、B和C四个OB结构域组成，它特异地结合端粒重复序列并对端粒重复序列的持续添加（RAP）很重要。生化结果及9.4 Å分辨率的端粒全酶结构均提示Teb1可以和端粒酶N端的TEN结构域相互作用，而TEN也可以特异结合端粒ssDNA，为端粒酶酶活性、RAP所必需。但它们的作用机制尚未被阐释。新鉴定的Teb1结合蛋白Teb2和Teb3，极可能稳定Teb1和端粒酶的作用。我们已获得Teb1C-Teb2N-Teb3（TEB）的初筛晶体，证实了TEB和TEN的相互作用，为解析TEB、TEB-TEN高分辨率晶体结构、阐释其作用机制奠定了基础。该研究将为研究高等生物端粒酶酶活性的调节提供重要指导。