Research Article

Structure of Tetrahymena telomerase reveals previously unknown subunits, functions, and interactions

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Science  15 Oct 2015:
DOI: 10.1126/science.aab4070

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Telomerase helps maintain telomeres by processive synthesis of telomere repeat DNA at their 3′-ends using an integral telomerase RNA (TER) and telomerase reverse transcriptase (TERT). We report the cryoelectron microscopy structure of Tetrahymena telomerase at ~9 Å resolution. In addition to 7 known holoenzyme proteins, 2 new proteins are identified, which form a complex (TEB) with single-stranded telomere DNA-binding protein Teb1, paralogous to heterotrimeric Replication Protein A (RPA). The p75-p45-p19 subcomplex is identified as another RPA-related complex, CST. This study reveals the paths of TER in the TERT-TER-p65 catalytic core and ssDNA exit, extensive subunit interactions of TERT essential N-terminal domain, p50, and TEB, and new subunit identities and structures, including p19 and p45C crystal structures, providing unprecedented structural and mechanistic insights into telomerase holoenzyme function.

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