Cloning of human telomeres by complementation in yeast

TELOMERES confer stability on chromosomes by protecting them from degradation and recombination and by allowing complete replication of the end1. They are genetically important as they define the ends of the linkage map. Telomeres of lower eukaryotes contain short repeats consisting of a G-rich and a C-rich strand, the G-rich strand running 5′–3′ towards the telomere and extending at the end2–11. Telomeres of human chromosomes share characteristics with those of lower eukaryotes12, 13, including sequence similarity as detected by cross-hybridization14–16. Telomeric repeats from many organisms can provide telomere function in yeast2, 17. Here we describe a modified yeast artificial chromosome (YAC) vector with only one telomere which we used to clone human telomeres by complementation in yeast. YACs containing human telomeres were identified by hydridization to an oligonucleotide of the trypanosome telomeric repeat. A subcloned human fragment from one such YAC is immediately subtelomeric on at least one human chromosome.