Characterization of telomeric regions from Ustilago maydis.

The isolation of telomeres from the phytopathogenic fungus Ustilago maydis is described. The telomeric repeat from the plant Arabidopsis thaliana, TTTAGGG, cross-hybridizes to Bal31-sensitive fragments of U. maydis DNA and detects many or all of the U. maydis chromosomes separated by pulsed-field gel electrophoresis (PFGE). This telomeric repeat was used to screen a library enriched for chromosome ends. Three clones were isolated which contained the tandemly repeated sequence TTAGGG. This sequence is identical to some known telomere repeats found in humans and other vertebrates as well as in some protozoa and moulds. In addition, the three telomeric clones had an almost identical 376 bp segment of middle-repeated telomere-associated sequences adjacent to the telomeric repeat. This segment hybridized to many or all U. maydis chromosomes separated by PFGE and showed a hybridization pattern in genomic digestions similar to that of the telomeric repeat. These results indicate that in U. maydis the same segment of telomere-associated sequences is located adjacent to the telomeric repeat in many or all chromosomes, which suggests that it may have a common role in chromosome function.