The Leishmania major maxicircle divergent region is variable in different isolates and cell types

The maxicircle divergent region (DR) was partially sequenced in several isolates of Leishmania major. The sequence contains various repeated elements: two types of long GC-rich repeats alternating with clusters of short AT-rich repeats. The arrangement of repeats appears to be similar in the studied Leishmania species and their relative Leptomonas seymouri. Furthermore, a conserved sequence containing putative promoters within a palindrome was revealed in the DRs of these species. Unexpectedly, the DR sequence proved to be dissimilar in promastigotes and amastigotes of the same isolate perhaps through selection of parasites with particular maxicircle variants in the course of the promastigote–amastigote differentiation. Different number of repeats and numerous single nucleotide polymorphisms are observed in the compared sequences. We have also investigated the DR structure in 21 L. major isolates by PCR and demonstrated its great variability. We suppose, however, that different variants of the DR structure are generated by combination of several highly conserved domains.