LINKAGE OF 2 DISTINCT AT-RICH MINISATELLITES AT MULTIPLE LOCI IN THE GENOME OF THEILERIA-PARVA

Minisatellite tandem repeat elements are well known components of vert ebrate genomes, but have not yet been extensively characterized in low er eukaryotes. We describe two unusual, AT-rich minisatellites of the protozoan parasite Theileria parva whose sequences are unrelated to th e G/C-rich 'chi minisatellite superfamily' of vertebrate and plant gen omes. The T. parva tandem repeats, one with a conserved sequence T(2-5 )ACACA (6-17 copies), and the other with a 6-bp core sequence of eithe r ACTATA or TATACT associated with additional variable sequences in re peats of 10-17 bp (3-7 copies), were closely linked at more than 20 si tes in the T. parva genome, separated by 390, 510 and 660 bp at three loci analysed in detail. Such linkage is without precedent in minisate llites so far analysed in other organisms. The minisatellite loci were widely dispersed on 13 out of 33 genomic SfiI fragments, on all four T. pal va chromosomes and did not exhibit a telomeric bias in their di stribution. Analysis of flanking sequences revealed no obvious conserv ed sequences between the five loci, or other multicopy repeat sequence s outside the minisatellite regions. The T2-5 ACACA minisatellite was highly effective as a multilocus fingerprinting probe for discriminati on of T. parva isolates. Analysis of two individual minisatellite loci revealed variation between the genomic DNAs of two T. parva isolates in the copy number of the constituent repeats within the array, simila r to that typical of vertebrate minisatellites. (C) 1998 Elsevier Scie nce B.V. All rights reserved.