Medical Systems Biology, Faculty of Medicine Carl Gustav Carus, University Cancer Center, Dresden University of Technology, 01307 Dresden, Germany.
EMBO J. 2013 Jun 12;32(12):1681-701. doi: 10.1038/emboj.2013.105. Epub 2013 May 17.
Telomeres are repetitive DNA structures that, together with the shelterin and the CST complex, protect the ends of chromosomes. Telomere shortening is mitigated in stem and cancer cells through the de novo addition of telomeric repeats by telomerase. Telomere elongation requires the delivery of the telomerase complex to telomeres through a not yet fully understood mechanism. Factors promoting telomerase-telomere interaction are expected to directly bind telomeres and physically interact with the telomerase complex. In search for such a factor we carried out a SILAC-based DNA-protein interaction screen and identified HMBOX1, hereafter referred to as homeobox telomere-binding protein 1 (HOT1). HOT1 directly and specifically binds double-stranded telomere repeats, with the in vivo association correlating with binding to actively processed telomeres. Depletion and overexpression experiments classify HOT1 as a positive regulator of telomere length. Furthermore, immunoprecipitation and cell fractionation analyses show that HOT1 associates with the active telomerase complex and promotes chromatin association of telomerase. Collectively, these findings suggest that HOT1 supports telomerase-dependent telomere elongation.
端粒是重复 DNA 结构，与 shelterin 和 CST 复合物一起保护染色体末端。端粒缩短在干细胞和癌细胞中通过端粒酶从头添加端粒重复序列来缓解。端粒延长需要通过尚未完全了解的机制将端粒酶复合物递送到端粒。促进端粒酶-端粒相互作用的因素预计将直接结合端粒并与端粒酶复合物进行物理相互作用。在寻找这样的因素时，我们进行了基于 SILAC 的 DNA-蛋白质相互作用筛选，并鉴定了 HMBOX1，以下称为同源盒端粒结合蛋白 1（HOT1）。HOT1 直接且特异性地结合双链端粒重复序列，体内关联与主动加工的端粒结合相关。耗尽和过表达实验将 HOT1 归类为端粒长度的正调节剂。此外，免疫沉淀和细胞分级分析表明，HOT1 与活性端粒酶复合物结合，并促进端粒酶与染色质的结合。总之，这些发现表明 HOT1 支持端粒酶依赖性端粒延长。
