THE SACCHAROMYCES RETROTRANSPOSON TY5 INFLUENCES THE ORGANIZATION OF CHROMOSOME ENDS

Retrotransposons are ubiquitous components of eukaryotic genomes sugge sting that they have played a significant role in genome organization, In Saccharomyces cerevisiae, eight of 10 endogenous insertions of the Ty5 retrotransposon family are located within 15 kb of chromosome end s, and two are located near the subtelomeric HMR locus, This genomic o rganization is the consequence of targeted transposition, as 14 of 15 newly transposed Ty5 elements map to telomeric regions on 10 different chromosomes, Nine of these insertions are within 0.8 kb and three are within 1.5 kb of the autonomously replicating consensus sequence in t he subtelomeric X repeat. This suggests that the X repeat plays an imp ortant role in directing Ty5 integration, Analysis of endogenous inser tions from S.cerevisiae and its close relative S.paradoxus revealed th at only one of 12 insertions has target site duplications, indicating that recombination occurs between elements, This is further supported by the observation that Ty5 insertions mark boundaries of sequence dup lications and rearrangements in these species, These data suggest that transposable elements like Ty5 can shape the organization of chromoso me ends through both transposition and recombination.