Telomere telomere recombination provides an express pathway for telomere acquisition

Abstract

DNA termini from Tetrahymena and Oxytricha, which bear C₄A₂ and C₄A₂ repeats respectively, can support telomere formation in Saccharomyces cerevisiae by serving as substrates for the addition of yeast telomeric C_1-3A repeats. Previously, we showed that linear plasmids with 108 base pairs of C₄A₄DNA (YL_p108CA) efficiently acquired telomeres, whereas plasmids containing 28,64 base pairs of C₄A₄ DNA also promoted telomere formation, but with reduced efficiency¹. Although many of the C₄A₄ termini on these plasmids underwent recombination with a C₄A₂ terminus, the mechanism of telomere-telomere recombination was not established^1,3. We now report the sequence of the C₄A₄ ends from the linear plasmids. The results provide strong evidence for a novel recombination process involving a gene conversion event that requires little homology, occurs at or near the boundary of telomeric and non-telomeric DNA, and resembles the recombination process involved in bacteriophage T4 DNA replication.