PNEUMOCYSTIS-CARINII TELOMERE REPEATS ARE COMPOSED OF TTAGGG AND THE SUBTELOMERIC SEQUENCE CONTAINS A GENE ENCODING THE MAJOR SURFACE GLYCOPROTEIN

We have cloned a telomere and adjacent sequences from rat-derived Pneu mocystis carinii using the ability of foreign telomeres to complement a yeast artificial chromosome (YAC) deficient by one telomere in Sacch aromyces cerevisiae. Characterization of the cloned DNA in the recombi nant YAC demonstrated that it was a chimera of two P. carinii sequence s, namely a 13.5 kb fragment of mitochondrial DNA and an 8.3 kb distal portion consisting of subtelomeric DNA. The P. carinii telomere repea t was demonstrated to be TTAGGG, the most common telomere repeat found in organisms from the animal and fungal kingdoms. Karyotype analysis confirmed that this sequence was present on all the P. carinii chromos omes. Sequence adjacent to the telomere repeats was shown by Bal3l exo nuclease digestion to be located at the chromosome ends. Analysis of t he subtelomeric fragment revealed homology to the gene encoding the ma jor surface glycoprotein of P. carinii.