Understanding diversity in telomere dynamics.

Abstract

Telomeres and their associated proteins constitute an ancient and highly conserved system to maintain chromosome stability and the integrity of the coding sequences in eukaryote genomes. They identify and protect the chromosome ends. While other linear chromosome-capping mechanisms also occur in nature [1], the telomeric system appears to be the most common. Many operational principles of this system are shared across a wide range of eukaryote species, indicative of its ancient origins. Telomere DNA generally comprises a string of a repeated, short, non-coding sequence, which is often G rich, such as TTAGGG [2]. The proximal end of the telomeric tract is double stranded, and the distal end terminates in a single-stranded overhang of the G-rich strand. The structure loops back on itself and the single-stranded section intrudes into the double-stranded telomeric DNA. Specific protein complexes, termed the shelterin and CST complexes, help to maintain the t-loop structure and regulate telomere access during DNA replication (e.g. for review, see [3]). Processes occur within cells not only to maintain telomere structure, but also to restore the loss of telomeric DNA that occurs as a natural consequence of the DNA replication process. Until relatively recently, almost all of the work on telomeres was in the context of understanding how malfunctioning of this system of chromosome protection can lead to human disease. However, there has been a burgeoning of interest in looking at how the telomere system operates in different kinds of animals, and in understanding variation in telomere dynamics and in the expression of telomerase in species with different morphologies and life histories. This theme issue represents a relatively unusual coming together of scientists from different disciplinary backgrounds, including evolutionary biology, ecology, cell biology and biomedicine, to understand and elucidate the origins and diversity of telomere dynamics, …