Characterization of the Novel Mitochondrial Genome Segregation Factor TAP110 in Trypanosoma brucei

Abstract

Proper mitochondrial genome inheritance is key for eukaryotic cell survival, however little is known about the molecular mechanism controlling this process. Trypanosoma brucei, a protozoan parasite, contains a singular mitochondrial genome aka kinetoplast DNA (kDNA). kDNA segregation requires anchoring of the genome to the basal body via the tripartite attachment complex (TAC). Several components of the TAC as well as their assembly have been described, it however remains elusive how the TAC connects to the kDNA. Here, we characterize the TAC associated protein TAP110 and for the first time use ultrastructure expansion microscopy in trypanosomes to reveal that TAP110 is the currently most proximal kDNA segregation factor. The kDNA proximal positioning is also supported by RNAi depletion of TAC102, which leads to loss of TAP110 at the TAC. Overexpression of TAP110 leads to expression level changes of several mitochondrial proteins and a delay in the separation of the replicated kDNA networks. In contrast to other kDNA segregation factors TAP110 remains only partially attached to the flagellum after DNAse and detergent treatment and can only be solubilized in dyskinetoplastic cells, suggesting that interaction with the kDNA might be important for stability of the TAC association. Furthermore, we demonstrate that the TAC, but not the kDNA, is required for correct TAP110 localization in vivo and suggest that TAP110 might interact with other proteins to form a >669 kDa complex. Summary StatementTAP110 is a novel mitochondrial genome segregation factor in Trypanosoma brucei that associates with the previously described TAC component TAC102. Ultrastructure expansion microscopy reveals its proximal position to the kDNA.