Tetraplex structure of budding yeast telomeric DNA.

We examined the structural properties of budding yeast telomeric DNA sequences, SCTELG4: 5'-(TGGG TGTG)(4)-3' and SCTELGG4: 5'-(TGGGTGTGG)(4)-3', in the presence of Na(+) or K(+). The conformation of SCTELG4 with Na(+) was a mixture of parallel tetraplex DNA and unstructured single-stranded DNA. On the other hand, the conformation of SCTELGG4 with Na(+) was a mixture of parallel and antiparallel tetraplex DNA. The ratio of the amount of parallel tetraplex to that of unstructured single-strand was increased for SCTELG4 by the presence of K(+). The conformation of almost all of SCTELGG4 was changed into parallel tetraplex by the presence of K(+). These results indicate that structural change of SCTELG4 and SCTELGG4 may be induced by the type of cation. We conclude that the conformation of budding yeast telomeric DNA sequences depends on the base sequence and the type of cation.