| Sumario: | Theileria parva, an intra-cellular protozoan parasite of cattle, causes a
lymphoproliferative disease called East Coast fever. The parasite genome is
considered to be haploid in both the sporozoite and piroplasm stages of its life cycle
while the schizont stages are polyploid. The piroplasm has four chromosomes and
hence eight telomeres (reviwed in Morzaria and Young, 1992). The work reported here
is based on the finding that Theileria parva sub telomeric DNAs contain open reading
frames, which potentially secrete proteins (Sohanpal et al., 1995). The main objective
of this project was to identify additional schizont cDNAs on different telomeric regions.
However, due to problems associated with the purification of large parasite genomic
DNAs from gels, the study concentrated on identifying cDNAs located centromere
proximal to the subtelomeric DNA on the right arm of chromosome three of the parasite
genome.
A 60kb piroplasm genomic DNA, spannmg the SftI site between DNA
fragments 17 and 22 was isolated from an arrayed pBeioBAC11library of the Theileria
parva genome and used to probe a total parasite (schizont) RNA blot in order to
determine its transcription profile. No homology was however, detected. This was
probably due to lack of sensitivity to the-)nRNA by the probe due to presence of the ,,~ .
former in low copy numbers. The 60kb DNA-, fragment was also used to screen a library
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of bacteriophage A clones containing 11. parva schizont cDNA. Four positive clones
were isolated and these were characterised by partial sequencing and data-base
searches. 75% of the schizont cDNAs, representing three different transcripts, were
found to express significant homology with genes described in organisms other than
Theileria parva, suggesting that the sequence is conserved between species. 50% of the
transcripts were found to be homologues of ribosomal genes encoding the S3a protein,
67 kDa laminin binding protein and the 67 kDa laminin receptor, all of which, under
certain circumstances, play important roles during transformation of cells (Nelson and
Hirumi, 1981; Masse et al., 1990). 25% of the schizont cDNAs, represented by one
transcript, expressed a significant homology with the nucleotide sequence from one
locus of chromosome III in Caenorhabditis elegans. The remaining 25% of the schizont
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