RT Journal Article
SR Electronic
T1 Structure of telomerase-bound CST with Polymerase α-Primase
JF bioRxiv
FD Cold Spring Harbor Laboratory
SP 2021.12.28.474374
DO 10.1101/2021.12.28.474374
A1 Yao He
A1 He Song
A1 Henry Chan
A1 Yaqiang Wang
A1 Baocheng Liu
A1 Lukas Susac
A1 Z. Hong Zhou
A1 Juli Feigon
YR 2021
UL http://biorxiv.org/content/early/2021/12/28/2021.12.28.474374.abstract
AB Telomeres are the physical ends of linear chromosomes, composed of short repeating sequences (e.g. TTGGGG in Tetrahymena for the G-strand) of double-stranded DNA with a single-strand 3’-overhang of the G-strand and a group of proteins called shelterin1,2. Among these, TPP1 and POT1 associate with the 3’-overhang, with POT1 binding the G-strand3 and TPP1 recruiting telomerase via interaction with telomerase reverse transcriptase (TERT)4. The ends of the telomeric DNA are replicated and maintained by telomerase5, for the G-strand, and subsequently DNA Polymerase α-Primase6,7 (PolαPrim), for the C-strand8. PolαPrim is stimulated by CTC1–STN1–TEN1 (CST)9–12, but the structural basis of both PolαPrim and CST recruitment to telomere ends remains unknown. Here we report cryo-EM structures of Tetrahymena CST in the context of telomerase holoenzyme, both in the absence and presence of PolαPrim, as well as of PolαPrim alone. Ctc1 binds telomerase subunit p50, a TPP1 ortholog, on a flexible Ctc1 binding motif unveiled jointly by cryo-EM and NMR spectroscopy. PolαPrim subunits are arranged in a catalytically competent conformation, in contrast to previously reported autoinhibited conformation. Polymerase POLA1 binds Ctc1 and Stn1, and its interface with Ctc1 forms an entry port for G-strand DNA to the POLA1 active site. Together, we obtained a snapshot of four key players required for telomeric DNA synthesis in a single complex—telomerase core RNP, p50/TPP1, CST and PolαPrim—that provides unprecedented insights into CST and PolαPrim recruitment and handoff between G-strand and C-strand synthesis.Competing Interest StatementThe authors have declared no competing interest.