Sequence analysis of the right end of chromosome XV in Saccharomyces cerevisiae: an insight into the structural and functional significance of sub-telomeric repeat sequences.

Approximately 3.9 kb of DNA, centromere proximal to the previously sequenced Y' element at the right end of chromosome XV in Saccharomyces cerevisiae strain YP1, has been sequenced. A number of the known sub-telomeric repeat sequences were identified, including Y', core X and STRs A, B. C and D. Several of these repeat elements contain potentially functional sequences. In addition, two other members of repeated gene families were identified. The first of these shows 61% and 60% DNA sequence identity to Enolases 1 and 2 respectively. The Enolase-like sequence appears to be species specific, with three copies being found in all strains of S. cerevisiae studied. The location of the three copies is the same for all strains. The second repeated sequence has homology with known open reading frames on chromosomes III, V and XI. There are five or six copies of this sequence in all S. cerevisiae and S. paradoxus strains studied and three in S. bayanus strains. The analysis of this region and comparison to sub-telomeric regions on other chromosomes gives some indication as to the potential functional and structural significance of sub-telomeric repeat sequences. In addition, these findings are consistent with the idea that sub-telomeric regions may be targets for unusual recombination events.