Volume 31, No 12, Dec 2021

ISSN: 1001-0602 
EISSN: 1748-7838 2018 
impact factor 17.848* 
(Clarivate Analytics, 2019)

Volume 31 Issue 12, December 2021: 1275-1290   |  Open Access

ORIGINAL ARTICLES

Zipper head mechanism of telomere synthesis by human telomerase

Futang Wan^1,2,† , Yongbo Ding^3,4,† , Yuebin Zhang^5,† , Zhenfang Wu^1,2,† , Shaobai Li^1,2 , Lin Yang^1,2 , Xiangyu Yan^1,2 , Pengfei Lan^6,7 , Guohui Li^5,* , Jian Wu^1,2,* , Ming Lei^1,2,7,*

¹Ninth People’s Hospital, Shanghai Jiao Tong University School of Medicine, Shanghai, China
²Shanghai Institute of Precision Medicine, Shanghai, China
³CAS Center for Excellence in Molecular Cell Science, Shanghai Institute of Biochemistry and Cell Biology, Chinese Academy of Sciences, Shanghai, China
⁴University of Chinese Academy of Sciences, Beijing, China
⁵Laboratory of Molecular Modeling and Design, State Key Laboratory of Molecular Reaction Dynamics, Dalian Institute of Chemical Physics, Chinese Academy of Sciences, Dalian, Liaoning, China
⁶Renji Hospital, Shanghai Jiao Tong University School of Medicine, Shanghai, China
⁷State Key Laboratory of Oncogenes and Related Genes, Shanghai Jiao Tong University School of Medicine, Shanghai, China
^†These authors contributed equally: Futang Wan, Yongbo Ding, Yuebin Zhang, Zhenfang Wu
Correspondence: Guohui Li(ghli@dicp.ac.cn)Jian Wu(wujian@shsmu.edu.cn)Ming Lei(leim@shsmu.edu.cn)

Telomerase, a multi-subunit ribonucleoprotein complex, is a unique reverse transcriptase that catalyzes the processive addition of a repeat sequence to extend the telomere end using a short fragment of its own RNA component as the template. Despite recent structural characterizations of human and Tetrahymena telomerase, it is still a mystery how telomerase repeatedly uses its RNA template to synthesize telomeric DNA. Here, we report the cryo-EM structure of human telomerase holoenzyme bound with telomeric DNA at resolutions of 3.5 Å and 3.9 Å for the catalytic core and biogenesis module, respectively. The structure reveals that a leucine residue Leu980 in telomerase reverse transcriptase (TERT) catalytic subunit functions as a zipper head to limit the length of the short primer–template duplex in the active center. Moreover, our structural and computational analyses suggest that TERT and telomerase RNA (hTR) are organized to harbor a preformed active site that can accommodate short primer–template duplex substrates for catalysis. Furthermore, our findings unveil a double-fingers architecture in TERT that ensures nucleotide addition processivity of human telomerase. We propose that the zipper head Leu980 is a structural determinant for the sequence-based pausing signal of DNA synthesis that coincides with the RNA element-based physical template boundary. Functional analyses unveil that the non-glycine zipper head plays an essential role in both telomerase repeat addition processivity and telomere length homeostasis. In addition, we also demonstrate that this zipper head mechanism is conserved in all eukaryotic telomerases. Together, our study provides an integrated model for telomerase-mediated telomere synthesis.

https://doi.org/10.1038/s41422-021-00586-7

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