Regulation of telomere length and function by a Myb-domain protein in fission yeast

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Abstract
Telomeres, the specialized nucleoprotein structures that comprise the ends of eukaryotic chromosomes1,2, are essential for complete replication3–5, and regulation of their length has been a focus of research on tumorigenesis6–8. In the budding yeast Saccharomyces cerevisiae, the protein Raplp binds to telomeric DNA and functions in the regulation of telomere length9–12. A human telomere protein, hTRF (human TTAGGG repeat factor) binds the telomere sequence in vitro13 and localizes to telomeres cytologically14, but its functions are not yet known. Here we use a genetic screen to identify a telomere protein in fission yeast, Tazlp (telomere-associated in Schizosaccharomyces pombe), that shares homology to the Myb proto-oncogene DNA-binding domain with hTRF. Disruption or deletion of the taz1+ gene causes a massive increase in telomere length. Tazlp is required for the repression of telomere-adjacent gene expression and for normal meiosis or sporulation. It may be a negative regulator of the telomere-replicating enzyme, telomerase1,3, or may protect against activation of telomerase-independent pathways of telomere elongation8.