THE TELOMERE-ASSOCIATED DNA FROM HUMAN-CHROMOSOME 20P CONTAINS A PSEUDOTELOMERE STRUCTURE AND SHARES SEQUENCES WITH THE SUBTELOMERIC REGIONS OF 4Q AND 18P

The human chromosome 20p telomere has been cloned on a yeast artificia l chromosome (YAC). The telomere-associated DNA contains an interstiti al tract of (TTAGGG)(n) telomeric repeats 60 kb in from the chromosome end. Frequent truncation of the YAC clone was observed due to resolut ion of the internal telomeric array into a telomere. The 20p internal telomeric repeat tract is flanked on its centromeric side by telomere- associated repeated sequences that have previously been found adjacent to terminal telomeric repeat arrays, The pseudotelomere structure of the 20p subtelomeric region is similar to the structure of some yeast subtelomeric regions where these sequences act as substrates for recom binational repair of chromosome ends that have lost their terminal tel omeric repeat arrays, Sequences flanking the telomeric end of the inte rnal (TTAGGG)(n) repeat array on 20p are found adjacent to three other subtelomeric (TTAGGG)(n) tracts on 4q, 18p, and an unknown. chromosom e end, respectively. These shared sequences provide evidence of exchan ge between nonhomologous chromosomes in humans, (C) 1997 Academic Pres s.