leishmania is a protozoan parasite belonging to the family trypanosomatidae, which is found among 88 different countries. the parasite lives as an amastigote in vertebrate macro­phages and as a promastigote in the digestive tract of sand fly. it can be cultured in the laboratory us­ing appropriate culture media. although the sexual cycle of leishmania has not been observed during the promastigo...

Kinetoplast DNA (kDNA), the trypanosomatid mitochondrial DNA, is a network containing several thousand interlocked minicircles. During kDNA synthesis, minicircles dissociate from the network, and after replication their progeny reattach to the network periphery. Using electron microscopy autoradiography, we found that newly synthesized 3H-labeled minicircles, after short labeling periods, are c...

The mitochondrial genome of Trypanosoma brucei, called kinetoplast DNA, is a network of topologically interlocked DNA rings including several thousand minicircles and a few dozen maxicircles. Kinetoplast DNA synthesis involves release of minicircles from the network, replication of the free minicircles and reattachment of the progeny. Here we report a new function of the mitochondrial topoisome...

A sequence-specific single-stranded DNA-binding protein from the trypanosomatid protozoan Crithidia fasciculata binds to a sequence of 12 nucleotides located at the origin of replication of kinetoplast DNA minicircles. This sequence, termed the universal minicircle sequence (UMS), is conserved in the kinetoplast DNA minicircles among species of the family Trypanosomatidae. The purified protein ...

DNA topoisomerase activity detected in cell extracts of the trypanosomatid Crithidia fasciculata interlocks kinetoplast DNA duplex minicircles into huge catenane forms resembling the natural kinetoplast DNA networks found in trypanosomes. Catenation of duplex DNA circles is reversible and equilibrium is affected by ionic strength, and by spermidine. The reaction requires magnesium, is ATP depen...

Kinetoplast DNA, a giant network of interlocked DNA circles, replicates by an unusual mechanism. Minicircles are released individually from the network by a topoisomerase II, and then, after replication, their progeny are reattached at antipodal positions on the network periphery. Studies to date have revealed two distinct variations on this model. In Crithidia fasciculata the newly replicated ...

We have used immunofluorescent detection of 5-bromo-2-deoxyuridine-substituted DNA in order to determine the timing of initiation and the duration of nuclear and kinetoplast S-phases within the procyclic stage of the Trypanosoma brucei cell cycle. Both nuclear and kinetoplast S-phases were shown to be periodic, occupying 0.18 and 0.12 of the unit cell cycle, respectively. In addition, initiatio...

A 414-base pair fragment from a Leishmania tarentolae kinetoplast DNA minicircle has unusual physical properties. We reported previously that in comparison to phi X174 and pBR322 control fragments, the kinetoplast fragment behaves in gel electrophoresis, gel filtration, and electric dichroism experiments as if it has an unusually compact conformation. We accounted for these unusual properties b...

Newly replicated duplex DNA minicircles of trypanosomal kinetoplast DNA are nicked in both their monomeric and catenated topological states, whereas mature ones are covalently sealed. The possibility that nicking may play a role during kinetoplast DNA replication by affecting the topological interconversions of monomeric DNA minicircles and catenane networks was studied here in vitro using Crit...

Trypanosoma brucei has two DNA compartments: the nucleus and the kinetoplast. DNA replication of these two compartments only partially coincides. Woodward and Gull [Woodward R, Gull K. Timing of nuclear and kinetoplast DNA replication and early morphological events in the cell cycle of Trypanosoma brucei. J Cell Sci 1990;95:49-57] comprehensively studied the relative timing of the replication a...