MOLECULAR ANALYSIS OF A NOVEL SUBTELOMERIC REPEAT WITH POLYMORPHIC CHROMOSOMAL DISTRIBUTION

DNA from a 50-kb yeast artificial chromosome (YAC) containing one huma n telomere was characterized. Cloned sequences from the centromeric en d of this YAC (designated yRM2001) localized to several human chromoso mes by somatic hybrid panel mapping. The telomeric end of the YAC cont ained both (TTAGGG)(n) sequences and the previously characterized TelB am3.4 subterminal repeat element. A novel low-copy repeat element (des ignated HC1103) mapped 19 kb from the telomeric end of the YAC. This r epeat was shown by fluorescence in situ hybridization to be present in several subtelomeric regions (3q, 12p, 15q, 19p, and 20p) and at an i nterstitial site (2q13-->q14) in all individuals studied, but to be po lymorphically distributed at several other telomeres. The YAC vector-i nsert EcoRI cloning site was positioned 50 kb to 70 kb from chromosome termini in human genomic DNA using RecA-assisted restriction endonucl ease (RARE) cleavage analysis. Our results suggest that the DNA segmen t cloned in yRM2001 contains a novel block of low-copy DNA consistentl y present at some human telomeres, but polymorphically distributed at others.