Impaired maintenance of telomeres by telomerase causes cellular senescence and underlies many aging-related diseases in humans. Furthermore, telomere shortening is one of the most reproducible hallmarks of aging in human tissues, suggesting that telomere dysfunction contributes broadly to aging phenotypes in people. The human telomerase enzyme is comprised of a catalytic core ? the telomerase reverse transcriptase (TERT) and the telomerase RNA component (TERC) ? but also depends upon other holoenzyme proteins that bind the H/ACA element within TERC. During evolution, vertebrate telomerase hijacked this H/ACA sequence from other ancient non-coding RNAs, bringing the dyskerin core protein complex, which recognizes the H/ACA element, and TCAB1, which binds the CAB box element, into the telomerase holoenzyme. Telomerase function is critically dependent upon a series of steps, including assembly of the enzyme, trafficking within the nucleus, recruitment to telomeres and finally catalytic extension of telomeres. Each of these steps is poorly understood in humans and each step can be disrupted by germline mutations in patients with telomere diseases. The dyskerin complex is required for assembly and stability of telomerase. We identified TCAB1 as a protein that interacts with dyskerin and showed that TCAB1 binds the CAB box element common to TERC and to all small Cajal body RNAs (scaRNAs). We previously showed that TCAB1 is required for localization of telomerase in Cajal bodies, required for telomere maintenance and is important in recruitment to telomeres. We recently made the surprising finding that TCAB1 is also critical for telomerase catalytic activity and that TCAB1 is required for proper TERC conformation. Telomerase and other RNPs depend on an RNA molecule that needs to fold in a precise conformation, and this correct conformation represents one of countless potential structures. In this proposal, we pursue the hypothesis that TCAB1 is essential in shaping the telomerase RNA, and that this activity of TCAB1 is conserved in the splicing RNA pathway. We propose that the principal advantages conferred upon telomerase by adopting an H/ACA RNA fate is facilitating assembly and proper folding of TERC, and that numerous downstream steps depend upon this proper folding. We will pursue the following aims: (1) To understand how telomerase catalytic function depends upon TCAB1 (2) To determine how TCAB1 influences telomerase trafficking and recruitment (3) To determine how TCAB1 loss affects scaRNA function and RNA splicing.
The US population is rapidly aging, which is associated with an increase incidence of morbidity and aging-related disease. Despite intensive investigation, the underlying causes of human aging remain elusive. Shortening of telomeres is one of the most robust hallmarks of human aging. Furthermore, mutations and polymorphisms in telomerase genes predispose to diverse forms of aging-related disease in people. Telomere elongation strategies will require a more complete and mechanistic understanding of telomerase. We have identified TCAB1 as a key regulator of telomerase activity and function and propose to study this protein to understand how it controls telomerase and other small non-coding RNA-dependent processes.
| Chen, Lu; Roake, Caitlin M; Freund, Adam et al. (2018) An Activity Switch in Human Telomerase Based on RNA Conformation and Shaped by TCAB1. Cell 174:218-230.e13 |
| Lin, Shengda; Nascimento, Elisabete M; Gajera, Chandresh R et al. (2018) Distributed hepatocytes expressing telomerase repopulate the liver in homeostasis and injury. Nature 556:244-248 |
| Garbuzov, Alina; Pech, Matthew F; Hasegawa, Kazuteru et al. (2018) Purification of GFR?1+ and GFR?1- Spermatogonial Stem Cells Reveals a Niche-Dependent Mechanism for Fate Determination. Stem Cell Reports 10:553-567 |
