SACCHAROMYCES-CEREVISIAE TELOMERES - A REVIEW

Recent work has yielded considerable information concerning the struct ure and function of telomeres and their associated sequences in the bu dding yeast Saccharomyces cerevisiae. The structure and maintenance of telomeres depends not only on the RNA template and the catalytic subu nit of telomerase, but on a number of other proteins, These include pr oteins involved in assessing DNA damage and cell cycle regulation. The re are also non-telomerase mediated processes involved in the normal m aintenance of telomeres. In addition to proteins involved in telomere maintenance, there are a number of other proteins involved in the chro matin structure of the region. Many of these proteins have roles in si lencing, ageing, segregation and nuclear architecture, ?he structure o f the subtelomeric regions has been well characterized and consists of a mosaic of repeats found in variable copy numbers and locations. Ami dst the variable mosaic elements there are small conserved sequences f ound at all ends that may have functional roles. Recent work shows tha t the subtelomeric repeats can rescue chromosome ends when telomerase fails, buffer subtelomerically located genes against transcriptional s ilencing, and protect the genome from deleterious rearrangements due t o ectopic recombination, Thus the telomeres of yeast have a variety of roles in the life of the yeast cell beyond the protection crf the end s and overcoming the end replication problem associated with linear mo lecules.