Telomere Biology—Insights into an Intriguing Phenomenon
Department of Physiology, Yong Loo Lin School of Medicine, National University of Singapore, 117597 Singapore, Singapore
Clinical Research Unit, Khoo Teck Puat Hospital, 768828 Singapore, Singapore
Tembusu College, National University of Singapore, 138598 Singapore, Singapore
VIT University, Vellore 632014, India
Mangalore University, Mangalore 574199, India
Author to whom correspondence should be addressed.
Academic Editor: Alexander E. Kalyuzhny
Cells 2017, 6(2), 15; https://doi.org/10.3390/cells6020015
Received: 24 March 2017 / Revised: 9 June 2017 / Accepted: 13 June 2017 / Published: 19 June 2017
(This article belongs to the Special Issue DNA Repair Defects and Telomere Dysfunction in Diseases)
Bacteria and viruses possess circular DNA, whereas eukaryotes with typically very large DNA molecules have had to evolve into linear chromosomes to circumvent the problem of supercoiling circular DNA of that size. Consequently, such organisms possess telomeres to cap chromosome ends. Telomeres are essentially tandem repeats of any DNA sequence that are present at the ends of chromosomes. Their biology has been an enigmatic one, involving various molecules interacting dynamically in an evolutionarily well-trimmed fashion. Telomeres range from canonical hexameric repeats in most eukaryotes to unimaginably random retrotransposons, which attach to chromosome ends and reverse-transcribe to DNA in some plants and insects. Telomeres invariably associate with specialised protein complexes that envelop it, also regulating access of the ends to legitimate enzymes involved in telomere metabolism. They also transcribe into repetitive RNA which also seems to be playing significant roles in telomere maintenance. Telomeres thus form the intersection of DNA, protein, and RNA molecules acting in concert to maintain chromosome integrity. Telomere biology is emerging to appear ever more complex than previously envisaged, with the continual discovery of more molecules and interplays at the telomeres. This review also includes a section dedicated to the history of telomere biology, and intends to target the scientific audience new to the field by rendering an understanding of the phenomenon of chromosome end protection at large, with more emphasis on the biology of human telomeres. The review provides an update on the field and mentions the questions that need to be addressed.