ORGANIZATION OF MINI-EXON AND 5S RIBOSOMAL-RNA GENES IN THE KINETOPLASTID TRYPANOPLASMA-BORRELI

Mini-exon gene repeats from Trypanoplasma borreli, which belongs to th e Cryptobiidae family of the Bodonina suborder of the Kinetoplastida, were isolated by PCR amplification and cloning. The presence of kineto plastid-like mini-exon genes in T. borreli is consistent with the taxo nomic status of this organism as a kinetoplastid protozoan. Two famili es of repeats were found: 597 nt (T1) and 794 nt (T2), each of which e ncodes an approximately 95-nt medRNA transcript. The T1 repeats also c ontain a complete 5S rRNA gene on the complementary strand. The T2 rep eats contain a defective copy of a 5S gene, in which the 5' portion is absent. The intergenic regions between the 5'-ends of the mini-exon g enes and the 5S rRNA genes in the T1 and T2 repeats are highly diverge d. All or most mini-exon genes and 5S genes are located within either the T1 or the T2 repeats. The T1 repeats were localized to a megabase- size chromosome, while the T2 repeats were localized within at least 4 large chromosomes.