From mitochondrial DNA arrangement to repair: a kinetoplast-associated protein with different roles in two trypanosomatid species.

Background: One of the most intriguing and unusual features of trypanosomatids is their mitochondrial DNA, known as kinetoplast DNA (kDNA), which is organized into a network of concatenated circles. The kDNA is contained within the mitochondrial matrix and can exhibit distinct arrangements across different species and during cell differentiation. In addition to kDNA, the kinetoplast contains multiple proteins, including those involved in mitochondrial DNA topology and metabolism, such as the kinetoplast-associated proteins (KAPs). In this work, we obtained mutant cells to investigates the role of KAP7 in two trypanosomatid species, Trypanosoma cruzi and Angomonas deanei, which have distinct kinetoplast shapes and kDNA arrangements.

Methods: For this purpose, the kDNA replication process and cell morphology and ultrastructure were evaluated using microscopy methods. Furthermore, the proliferation of cells treated with genotoxic agents, such as cisplatin and ultraviolet radiation, was analyzed.

Results: In A. deanei, which contains a symbiotic bacterium, KAP7 seems to be essential, since the deletion of one KAP7 allele generated mutants with a decay in cell proliferation, as well as changes in kDNA structure and replication. In T. cruzi, null mutants exhibited disturbances in kDNA replication, although the overall topology remained unaltered. The use of cisplatin and ultraviolet (UV) radiation affected the ultrastructure of A. deanei and T. cruzi. Cisplatin promoted increased kDNA compaction in both KAP7 mutants, but only in T. cruzi did the proliferative capacity fail to recover after treatment, as was also observed following UV radiation exposure.

Conclusions: Proteins associated with DNA are evolutionarily conserved and usually perform similar functions in different organisms. Our findings reveal that KAP7 is involved in kDNA replication, but its roles differ in trypanosomatid species: in A. deanei, KAP7 is associated with kDNA arrangement, while in T. cruzi, it is related to mitochondrial metabolism, such as kDNA replication and damage response.