The chromosome ends of Saccharomyces cerevisiae are complex mosaics of several different types of telomeric and subtelomeric elements known as X element core sequences, X element combinatorial repeats, telomeric repeats, and Y' elements (2). The X element core sequence, a small conserved element of ~475 bp containing an ARS sequence and in most cases an Abf1p binding site, is the only region shared by all chromosome ends (2, 1). The X element combinatorial repeats, formerly known as subtelomeric repeats or STRs, are located between the X element core sequence and the telomeric end and are usually present as a combination of one or more of several types of smaller elements designated D, C, B, or A (2, 1). The telomeric repeat is a G-rich terminal sequence of the form (TG_1-3)_n that is maintained by telomerase (1). The Y' element is a helicase-encoding repetitive sequence found in many but not all subtelomeric regions next to the telomeric repeats, or adjacent X element combinatorial repeats, either as a single copy or tandem repeat of two to four copies (3, 1, 4). Possible functions of telomeric regions include roles in chromosomal segregation, maintenance of chromosome stability, recombinational sequestering, or as a barrier to transcriptional silencing (2, 1).

TEL06L, the left telomeric region of chromosome VI, is composed of an X element core sequence TEL06L-XC containing an ARS consensus sequence, an ABf1p binding site and a dubious ORF YFL063W, X element combinatorial repeats TEL06L-XR of the D, C, B and A types containing TBf1p binding sites, a stretch of telomeric repeats TEL06L-TR, and a short Y' (Y'-S) element TEL06L-YP containing a region of 36-bp repeats and five uncharacterized ORFs (YFL064C, YFL065C, YFL066C, YFL067W and YFL068W).

Click on the following figure for more details:

Further information can be found at the website of Dr. Ed Louis, Institute of Genetics, The University of Nottingham.

Last updated: 2003-10-29