Catenated dimers and knotted DNA structures: putative intermediates in the replication of T. cruzi kinetoplast minicircle DNA.

Upon centrifugation of gently lysed T. cruzi cells through a sucrose gradient, a free DNA fraction was shown to contain catenated dimers and knotted DNA structures. Southern hybridization and electron microscopic studies indicated that both of these structures derived from minicircle DNA, the major component of T. cruzi kinetoplast DNA. Partial denaturation analysis of a random population of catenated dimers suggests that these structures may have arisen from a late stage in the replication of minicircle DNA. On the other hand, the T. cruzi knotted minicircles we have isolated appear to be very similar to trefoil structures recently reported and implicated as replicative intermediates in two other trypanosoma species.