Download MendeleyStructure of Tetrahymena telomerase-bound CST with polymerase alpha-primase.
He, Y., Song, H., Chan, H., Liu, B., Wang, Y., Susac, L., Zhou, Z.H., Feigon, J.(2022) Nature 608: 813-818
- PubMed: 35831498
- DOI: https://doi.org/10.1038/s41586-022-04931-7
- Primary Citation of Related Structures:
7UY5, 7UY6, 7UY7, 7UY8 - PubMed Abstract:
Telomeres are the physical ends of linear chromosomes. They are composed of short repeating sequences (such as TTGGGG in the G-strand for Tetrahymena thermophila) of double-stranded DNA with a single-strand 3' overhang of the G-strand and, in humans, the six shelterin proteins: TPP1, POT1, TRF1, TRF2, RAP1 and TIN2 1,2 . TPP1 and POT1 associate with the 3' overhang, with POT1 binding the G-strand 3 and TPP1 (in complex with TIN2 4 ) recruiting telomerase via interaction with telomerase reverse transcriptase 5 (TERT). The telomere DNA ends are replicated and maintained by telomerase 6 , for the G-strand, and subsequently DNA polymerase α-primase 7,8 (PolαPrim), for the C-strand 9 . PolαPrim activity is stimulated by the heterotrimeric complex CTC1-STN1-TEN1 10-12 (CST), but the structural basis of the recruitment of PolαPrim and CST to telomere ends remains unknown. Here we report cryo-electron microscopy (cryo-EM) structures of Tetrahymena CST in the context of the telomerase holoenzyme, in both the absence and the presence of PolαPrim, and of PolαPrim alone. Tetrahymena Ctc1 binds telomerase subunit p50, a TPP1 orthologue, on a flexible Ctc1 binding motif revealed by cryo-EM and NMR spectroscopy. The PolαPrim polymerase subunit POLA1 binds Ctc1 and Stn1, and its interface with Ctc1 forms an entry port for G-strand DNA to the POLA1 active site. We thus provide a snapshot of four key components that are required for telomeric DNA synthesis in a single active complex-telomerase-core ribonucleoprotein, p50, CST and PolαPrim-that provides insights into the recruitment of CST and PolαPrim and the handoff between G-strand and C-strand synthesis.
Organizational Affiliation:
Department of Chemistry and Biochemistry, University of California, Los Angeles, Los Angeles, CA, USA.
