Cloning of Human Telomeres in Saccharomyces cerevisiae

Telomeres are specialized structures that form the ends of eukaryotic chromosomes and that are required to fulfill a number of varied functions, see Biessman and Mason for recent review (1 ). First, they must protect the chromosome ends from degradation and from fusion and recombination with other chromosome ends or internal DNA. They must also provide a solution to the problem of chromosome end replication, because all known polymerases require a primer and synthesize DNA from 5′-3′, therefore, the 3′ ends of linear DNA pose a problem to the normal replication machinery. They can influence gene expression by position effect variagation and finally, telomeres may play a role in establishing the architecture of the interphase and/or the meiotic prophase nucleus. Isolation of telomeric sequences is therefore of interest with respect to unraveling telomere structure and the mechanisms underlying telomeric function. In addition, the isolation and characterization of all human telomeres is a necessary part of the human genome project in order to generate genetic and physical markers at the ends of chromosomes thereby providing the boundaries of genetic and physical maps.