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 Pneumocystis carinii using the ability of foreign telomeres to complement a yeast artificial chromosome (YAC) deficient by one telomere in Saccharomyces cerevisiae. Characterization of the cloned DNA in the recombinant YAC demonstrated that it was a chimera of two P. carinii sequences, namely a 13.5 kb fragment of mitochondrial DNA and an 8.3 kb distal portion consisting of subtelomeric DNA. The P. carinii telomere repeat 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 chromosomes. Sequence adjacent to the telomere repeats was shown by Bal31 exonuclease digestion to be located at the chromosome ends. Analysis of the subtelomeric fragment revealed homology to the gene encoding the major surface glycoprotein of P. carinii.