CHARACTERIZATION OF THE TELOMERES AT OPPOSITE ENDS OF A 3 MB THEILERIA-PARVA CHROMOSOME

Bacteriophage lambda clones containing Theileria parva genomic DNA der ived from two different telomeres were isolated and the nucleotide seq uences of the telomeric repeats and adjacent telomere-associated (TAS) DNA were determined. The T.parva telomeric repeat sequences, a tandem array of TTTTAGGG or TTTAGGG interspersed with a few variant copies, showed a high degree of sequence identity to those of the photosynthet ic algae Chlamydomonas reinhardtii (97% identity) and Chlorella vulgar is (87.7% identity) and the angiosperm Arabidopsis thaliana (84.4% ide ntity). Unlike most organisms which have been studied, no significant repetitive sequences were found in the nucleotide sequences of TAS DNA located centromere-proximal to the telomeric repeats. Restriction map ping and hybridisation analysis of lambda EMBL3 clones containing 16 k ilobases of TAS DNA derived from one telomere suggested that they did not contain long regions of repetitive DNA, The cloned TAS DNAs were m apped to T.parva Muguga genomic Sfil fragments 8 and 20, which are loc ated at opposite ends of the largest T.parva chromosome. A 126 bp sequ ence located directly centromere-proximal to the telomeric repeats was 94% identical between the two cloned telomeres. The conserved 126 bp sequence was present on all T.parva Muguga telomeric Sfil fragments.