Project description:The Tripartite Attachment Complex (TAC) is essential for mitochondrial DNA (kDNA) segregation in Trypanosoma brucei, providing a physical link between the flagellar basal body and the mitochondrial genome. Although the TAC's hierarchical assembly and linear organization have been extensively studied, much remains to be discovered regarding its complete architecture and composition – for instance, our identification of a new TACcomponent underscores these knowledge gaps. Here, we use a combination of proteomics, RNA interference (RNAi), and Ultrastructure Expansion Microscopy (U-ExM) to characterize the TAC at high resolution and identify a novel component, TAC53 (Tb927.2.6100). Depletion of TAC53 in both procyclic and bloodstream forms results in kDNA missegregation and loss, a characteristic feature of TAC dysfunction. TAC53 localizes to the kDNA in a cell cycle-dependent manner and represents the most kDNA-proximal TAC component identified to date. U-ExM reveals a previously unrecognized tubular architecture of the TAC, with two distinct TAC structures per kDNA disc, suggesting a mechanism for precise kDNA alignment and segregation. Moreover, immunoprecipitation and imaging analyses indicate that TAC53 interacts with known TAC-associated proteins HMG44, KAP68, and KAP3, forming a network at the TAC–kDNA interface. These findings redefine our understanding of TAC architecture and function and identify TAC53 as a key structural component anchoring the mitochondrial genome in T. brucei.
Project description:The Tripartite Attachment Complex (TAC) is essential for mitochondrial DNA (kDNA) segregation in Trypanosoma brucei, providing a physical link between the flagellar basal body and the mitochondrial genome. Although the TAC's hierarchical assembly and linear organization have been extensively studied, much remains to be discovered regarding its complete architecture and composition – for instance, our identification of a new TACcomponent underscores these knowledge gaps. Here, we use a combination of proteomics, RNA interference (RNAi), and Ultrastructure Expansion Microscopy (U-ExM) to characterize the TAC at high resolution and identify a novel component, TAC53 (Tb927.2.6100). Depletion of TAC53 in both procyclic and bloodstream forms results in kDNA missegregation and loss, a characteristic feature of TAC dysfunction. TAC53 localizes to the kDNA in a cell cycle-dependent manner and represents the most kDNA-proximal TAC component identified to date. U-ExM reveals a previously unrecognized tubular architecture of the TAC, with two distinct TAC structures per kDNA disc, suggesting a mechanism for precise kDNA alignment and segregation. Moreover, immunoprecipitation and imaging analyses indicate that TAC53 interacts with known TAC-associated proteins HMG44, KAP68, and KAP3, forming a network at the TAC–kDNA interface. These findings redefine our understanding of TAC architecture and function and identify TAC53 as a key structural component anchoring the mitochondrial genome in T. brucei.
Project description:The near-minimal bacterium Mesoplasma florum constitutes an interesting model for synthetic genomics and systems biology studies due to its small genome, fast growth rate, and lack of pathogenic potential. However, some fundamental aspects of its biology remain largely unexplored. Here, we report a broad yet remarkably detailed characterization of M. florum by combining a wide variety of experimental approaches. More specifically, we investigated several physical and physiological aspects of this bacterium, and performed the first genome-wide analysis of its transcriptome and proteome using RNA sequencing techniques and two-dimensional liquid chromatography-tandem mass spectrometry. These analyses notably revealed the M. florum consensus promoter, a first experimental cartography of transcription units, as well as the transcription and expression levels of all annotated genes. We also converted gene transcription and expression levels into absolute molecular abundances using biomass quantification results, generating an unprecedented view of the M. florum cellular composition and functions. These characterization efforts will provide an experimental foundation for the development of a genome-scale metabolic model for M. florum and will guide future genome engineering endeavours in this simple organism.