Telomere binding of the Rap1 protein is required for meiosis in fission yeast

Telomeres are essential for chromosome integrity, protecting the ends of eukaryotic linear chromosomes during cell proliferation [1, 2]. Telomeres also function in meiosis; a characteristic clustering of telomeres beneath the nuclear membrane is observed during meiotic prophase in many organisms from yeasts to plants and humans [3-9], and the role of the telomeres in meiotic pairing and the recombination of homologous chromosomes has been demonstrated in the fission yeast Schizosaccharomyces pombe [9-14] and in the budding yeast Saccharomyces cerevisiae [15]. Here we report that S. pombe Rap1 is a telomeric protein essential for meiosis. While Rap1 is conserved in budding yeast and humans, schemes for telomere binding vary among species: human RAP1 binds to the telomere through interaction with the telomere binding protein TRF2 [16]; S. cerevisiae Rap1, however, binds telomeric DNA directly [17], and no orthologs of TRF proteins have been identified in this organism. In S. pombe, unlike in S. cerevisiae, an ortholog of human TRF has been identified. This ortholog, Taz1, binds directly to telomere repeats [18] and is necessary for telomere clustering in meiotic prophase [11, 12]. Our results demonstrate that S. pombe Rap1 binds to telomeres through interaction with Taz1, similar to human Rap1-TRF2, and that Taz1-mediated telomere localization of Rap1 is necessary for telomere clustering and for the successful completion of meiosis. Moreover, in taz1-disrupted cells, molecular fusion of Rap1 with the Taz1 DNA binding domain recovers telomere clustering and largely complements defects in meiosis, indicating that telomere localization of Rap1 is a key requirement for meiosis.