SUMMARY PARAGRAPH for TEL12L
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 (TG1-3)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).
One of the most complex of all telomeres, TEL12L, the left telomeric region of chromosome XII, is composed of an X element core sequence TEL12L-XC containing an ARS consensus sequence, an Abf1p binding site and a dubious ORF YLL065W, X element combinatorial repeats TEL12L-XR of the D, C, B and A types containing Tbf1p binding sites, followed by the first of three regions of telomeric repeats TEL12L-TR3, the first of two short Y' (Y'-S) elements TEL12L-YP2 containing an ARS consensus sequence, a region of 36-bp repeats, an uncharacterized ORF YLL066C and a dubious ORF YLL066W-A, the second region of telomeric repeats TEL12L-TR2 spanning an uncharacterized ORF YLL066W-B, the second short Y' element TEL12L-YP1 containing an ARS consensus sequence, a region of 36-bp repeats, an uncharacterized ORF YLL067C and a dubious ORF YLL067W-A, and a short terminal stretch of telomeric repeats TEL12L-TR1.
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