Structure of Telomerase with Telomeric DNA

Telomerase is an RNA–protein complex (RNP) that extends telomeric DNA at the 3′ ends of chromosomes using its telomerase reverse transcriptase (TERT) and integral template-containing telomerase RNA (TER). Its activity is a critical determinant of human health, affecting aging, cancer, and stem cell renewal. Lack of atomic models of telomerase, particularly one with DNA bound, has limited our mechanistic understanding of telomeric DNA repeat synthesis. We report the 4.8 Å resolution cryoelectron microscopy structure of active Tetrahymena telomerase bound to telomeric DNA. The catalytic core is an intricately interlocked structure of TERT and TER, including a previously structurally uncharacterized TERT domain that interacts with the TEN domain to physically enclose TER and regulate activity. This complete structure of a telomerase catalytic core and its interactions with telomeric DNA from the template to telomere-interacting p50–TEB complex provides unanticipated insights into telomerase assembly and catalytic cycle and a new paradigm for a reverse transcriptase RNP. [Display omitted] •Structure of Tetrahymena telomerase with telomeric DNA provides mechanistic insights•Complete architecture of catalytic core reveals a new structural motif named TRAP•Detailed path of DNA from active site to telomere DNA-binding p50–TEB complex•Roles for telomerase RNA TRE-template-TBE in telomeric DNA synthesis The cryo-EM structure of active Tetrahymena telomerase bound to telomeric DNA reveals unique insights into the catalytic core and DNA handling.