Abstract

Telomeres are stretches of TTAGGG nucleotide repeats located at the ends of linear chromosomes that shorten with progressive cell division and prevent genomic instability at the cost of limiting a cell’s capacity to proliferate. This limitation can be overcome by telomerase, a ribonucleoprotein complex that elongates telomeres via reverse-transcription of the template telomerase RNA component (TERC). Recent studies have reported potential functions of TERC outside of its role in telomere maintenance. These noncanonical functions of TERC are however poorly defined, and the molecular mechanisms and biological relevance behind such functions remain elusive. Here, we generated conditional TERC knock-out human embryonic stem cells (iTERC_KO hESCs) to uncouple TERC expression from telomere length maintenance in order to investigate the consequences of TERC ablation in the absence of telomere dysfunction. We found that deletion of TERC led to a synchronized, widespread induction of apoptosis in the absence of short or dysfunctional telomeres. This phenotype is not recapitulated in conditional telomerase reverse transcriptase (TERT) knock-out hESCs and can be prevented by expression of a TERC mutant RNA that fails to bind the remaining telomerase components dyskerin and TCAB1. Therefore, TERC has an essential function independent of the telomerase complex in hESCs. Conversely, we found that TERC is dispensable in somatic cells, indicating that the antiapoptotic role of TERC in hESCs is not universal across cell types. Finally, we report that TERC53, a short form of TERC processed in the mitochondria and exported to the cytosol, is necessary and sufficient to prevent apoptosis in iTERC_KO hESCs. These results support a model in which TERC53 acts in the cytosol outside of the telomerase complex to inhibit apoptosis and promote survival in human stem cells.

Committee Chair

Luis F. Batista

Committee Members

Sheila Stewart, Christopher Sturgeon, James Skeath, Sergei Djuranovic,

Comments

Permanent URL: https://doi.org/10.7936/r5pj-rx10

Degree

Doctor of Philosophy (PhD)

Author's Department

Biology & Biomedical Sciences (Molecular Genetics & Genomics)

Author's School

Graduate School of Arts and Sciences

Document Type

Dissertation

Date of Award

Winter 12-15-2019

Language

English (en)

Author's ORCID

http://orcid.org/0000-0002-8528-6233

Download

Included in

Biology Commons

Share

COinS