Specific discontinuities in Leishmania tarentolae minicircles map within universally conserved sequence blocks.

Specific discontinuities remaining in the daughter strands of newly synthesized minicircles from Crithidia fasciculata and Trypanosoma equiperdum have been shown to lie within conserved sequence blocks (CSBs) present in minicircles from all species of trypanosomes. The presence of ribonucleotides at the 5' ends of the L-strand in both cases suggests that the conserved sequences may constitute a replication origin. However, specific discontinuities have only been mapped in organisms having unusually homogeneous populations of minicircles. The specific nicks in minicircles from the heterogeneous population present in Leishmania tarentolae have now been mapped to predicted sites within the CSBs. These results are consistent with a universal mechanism of minicircle replication dictated by a conserve sequence motif present both in minicircles having a high degree of sequence heterogeneity as well as in relatively homogeneous populations.