Telomeres have been implicated in a number of cellular processes including aging, chromosome stability, meiosis, replication timing, transcriptional repression and the positioning of chromosomes within the nucleus. The primary goal of the laboratory is to understand the changes that telomeres undergo during tumorigenesis and how telomere dysfunction is linked to chromosomal instability. To gain a better understanding of the dynamic interactions that occur at the telomere we are reconstituting telomeric complexes in vitro and study the protective function of individual components and their effects on telomerase activity. Complementing these studies are several approaches aimed at dissecting the functions of telomeres within the cell. For example, deletion of the pot1+ gene in fission yeast causes rapid loss of telomeric sequences leading to chromosome instability and cell death. Genetic screens are now aimed at identifying the genes responsible for the degradation of telomeres in the absence of Pot1 and the activities that contribute to chromosome fusions and genomic instability.