TELOMERE TALES - CHROMATIN, TELOMERASE AND TELOMERE FUNCTION IN SACCHAROMYCES-CEREVISIAE

Unusual chromatin structures underlie epigenetic effects at the silent mating-type loci and telomeres in yeast. Many of the same genes appea r to function in transcriptional silencing observed at both the silent mating-type loci and at telomeres. The observation that these loci ar e united by a requirement for shared factors suggests that the structu re of chromatin al these regions is similar. Alteration of telomeric c hromatin components affects regulation of transcription, telomeric len gth, recombination and chromosomal stability. Mutations in TLC1 and ES T2, which both encode components of telomerase. cause identical phenot ypes: progressive shortening of telomeric DNA, increased chromosome lo ss and eventually cell death. In this review. we examine the relations hip between telomeric chromatin and telomere replication and discuss t he possibility that telomerase itself is an integral part of telomeric chromatin structure.