16 Fission Yeast Telomeres

Abstract

The fission yeast schizosaccharomyces pombe has a number of special characteristics that make it a convenient and illuminating model for studying telomere biology. First isolated from the cultures used to make beer in East Africa (pombe is a Swahili word for beer), S. pombe is a unicellular fungus that divides by medial fission. S. pombe is nearly as distant evolutionarily from budding yeast as it is from humans, having diverged from the budding yeast lineage more than 300 million years ago. The approximately 13.8-Mbp S. pombe genome contains about 4900 genes spread over only three chromosomes (Wood et al. 2002), housed in a nucleus that measures about 2 μm in diameter, centered in a 12-μm-long cell (Fig. 1). Facile transformation and integrative recombination provide an ease of genetic manipulation reminiscent of budding yeast. At the same time, fission yeast chromosome organization and dynamics are remarkably similar to those of humans. For example, fission yeast centromeres are large, complex, and heterochromatic, and fission yeast have a RNA interference (RNAi) pathway; both of these features, absent from Saccharomyces cerevisiae, are present in humans. Telomere protein organization is also highly reminiscent of that found in humans. This property, coupled with the small chromosome number that makes cytological studies and analysis of telomere fusions remarkably straightforward, has distinguished fission yeast as a paradigm for telomere research.

TELOMERE COMPONENTS AND ARCHITECTURE
Telomeric and Subtelomeric Sequences
Each telomere contains approximately 300 bp of a degenerate repeat sequence in which the most frequently occurring motif is TTACAGG,...