Characterization of the novel mitochondrial genome replication factor MiRF172 in Trypanosoma brucei

The unicellular parasite Trypanosoma brucei harbors one mitochondrial organelle with a singular genome called the kinetoplast DNA (kDNA). The kDNA consists of a network of concatenated minicircles and a few maxicircles that form the kDNA disc. More than 30 proteins involved in kDNA replication have been described. However, several mechanistic questions are only poorly understood. Here, we describe and characterize minicircle replication factor 172 (MiRF172), a novel mitochondrial genome replication factor that is essential for cell growth and kDNA maintenance. By performing super-resolution microscopy, we show that MiRF172 is localized to the kDNA disc, facing the region between the genome and the mitochondrial membranes. We demonstrate that depletion of MiRF172 leads to a loss of minicircles and maxicircles. Detailed analysis suggests that MiRF172 is involved in the reattachment of replicated minicircles to the kDNA disc. Furthermore, we provide evidence that the localization of the replication factor MiRF172 not only depends on the kDNA itself, but also on the mitochondrial genome segregation machinery, suggesting an interaction between the two essential entities.This article has an associated First Person interview with the first author of the paper.