SEQUENCE COMPARISON OF HUMAN AND YEAST TELOMERES IDENTIFIES STRUCTURALLY DISTINCT SUBTELOMERIC DOMAINS

We have sequenced and compared DNA from the ends of three human chromo somes: 4p, 16p and 22q, In all cases the pro-terminal regions are subd ivided by degenerate (TAGGG)(n) repeats into distal and proximal sub-d omains with entirely different patterns of homology to other chromosom e ends, The distal regions contain numerous, short (<2 kb) segments of interrupted homology to many other human telomeric regions, The proxi mal regions show much longer (similar to 10-40 kb) uninterrupted homol ogy to a few chromosome ends, A comparison of all yeast subtelomeric r egions indicates that they too are subdivided by degenerate TTAGGG rep eats into distal and proximal sub-domains with similarly different pat terns of identity to other non-homologous chromosome ends. Sequence co mparisons indicate that the distal and proximal sub-domains do not int eract with each other and that they interact quite differently with th e corresponding regions on other, non-homologous, chromosomes, These f indings suggest that the degenerate TTAGGG repeats identify a previous ly unrecognized, evolutionarily conserved boundary between remarkably different subtelomeric domains.