A Comprehensive Review on the Telomeric Repeat Sequence in Different Organisms

Telomeres protect the terminal ends of eukaryotic chromosomes, making them essential for genome stability, cellular senescence, and species evolution. These structures consist of tandem repeats of nucleotides, referred to as telomeric repeat sequences. The enzyme telomerase, along with various telomere-binding proteins, manages the synthesis of these repeat sequences. Telomerase functions by adding telomeric repeats to the ends of chromosomes, counteracting the shortening that occurs during DNA replication. In most somatic cells, telomerase activity is generally low or absent, leading to gradual telomere loss and, eventually, cellular senescence. Although the ancestral telomeric repeat sequence is often proposed to be TTAGGG, studies have shown that convergent evolution has produced similar telomeric motifs in various evolutionary lineages. This is evidenced by variations in telomeric repeat sequences among organisms, which may include single or double nucleotide substitutions, deletions, and even exceptionally large telomeric repeats in certain species. Investigating these telomeric repeat sequences across a wide range of organisms and identifying the evolutionary changes within each phylum offer valuable insights into telomeric sequences and the telomerases responsible for their synthesis. Such research not only deepens our understanding of telomere biology across different organisms but also holds potential for addressing age-related challenges and cancer, paving the way for innovative solutions to some of the most critical issues in contemporary medicine.   Received: 12 May 2024 | Revised: 29 October 2024 | Accepted: 11 November 2024   Conflicts of Interest The authors declare that they have no conflicts of interest to this work.   Data Availability Statement Data sharing is not applicable to this article as no new data were created or analyzed in this study.   Author Contribution Statement Monish Prasanna: Writing - Original Draft, Writing - Review & Editing. Kousik Varadan: Writing - Original Draft, Writing - Review & Editing. Achsha Babu: Writing - Original Draft, Writing - Review & Editing, Visualization, Supervision. Arun Arumugaperumal: Conceptualization, Supervision.