Biology subjects

Amodeo, S.

Publications and source records attributed to Amodeo, S..

3 recordsLinked to original sources

bioRxiv2017

Characterization of the Novel Mitochondrial Genome Replication Factor MiRF172 in Trypanosoma brucei

The unicellular parasite Trypanosoma brucei harbors one individual mitochondrial organelle with a singular genome the kinetoplast DNA or kDNA. The kDNA largely consists of concatenated minicircles and a few maxicircles that are also interlocked into 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 MiRF172, a novel mitochondrial genome replication factor, which is essential for proper cell growth and kDNA maintenance. Using super-resolution microscopy, we localize MiRF172 to the antipodal sites of the kDNA. We demonstrate that depletion of MiRF172 leads to continuous loss of mini- and maxicircles during the cell division cycle. Detailed analysis suggests that MiRF172 is likely 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 a tight interaction between the two essential entities.\n\nSummary StatementMiRF172 is a novel protein involved in the reattachment of replicated minicircles in Trypanosoma brucei, which requires the mitochondrial segregation machinery for proper localization.

cell biology↗

bioRxiv2017

A molecular model of the mitochondrial genome segregation machinery in Trypanosoma brucei

In almost all eukaryotes mitochondria maintain their own genome. Despite the discovery more than 50 years ago still very little is known about how the genome is properly segregated during cell division. The protozoan parasite Trypanosoma brucei contains a single mitochondrion with a singular genome the kinetoplast DNA (kDNA). Electron microscopy studies revealed the tripartite attachment complex (TAC) to physically connect the kDNA to the basal body of the flagellum and to ensure proper segregation of the mitochondrial genome via the basal bodies movement, during cell cycle. Using super-resolution microscopy we precisely localize each of the currently known unique TAC components. We demonstrate that the TAC is assembled in a hierarchical order from the base of the flagellum towards the mitochondrial genome and that the assembly is not dependent on the kDNA itself. Based on biochemical analysis the TAC consists of several non-overlapping subcomplexes suggesting an overall size of the TAC exceeding 2.8 mDa. We furthermore demonstrate that the TAC has an impact on mitochondrial organelle positioning however is not required for proper organelle biogenesis or segregation.\n\nSignificance StatementMitochondrial genome replication and segregation are essential processes in most eukaryotic cells. While replication has been studied in some detail much less is known about the molecular machinery required distribute the replicated genomes. Using super-resolution microscopy in combination with molecular biology and biochemistry we show for the first time in which order the segregation machinery is assembled and that it is assembled de novo rather than in a semi conservative fashion in the single celled parasite Trypanosoma brucei. Furthermore, we demonstrate that the mitochondrial genome itself is not required for assembly to occur. It seems that the physical connection of the mitochondrial genome to cytoskeletal elements is a conserved feature in most eukaryotes, however the molecular components are highly diverse.\n\nAbbreviation

cell biology↗

bioRxiv2017

The differentially expressed translationally controlled tumor proteins TCTP1 and TCTP2 in Trypanosoma brucei

1. SummaryIn Trypanosoma brucei we identified two TCTP genes differentially expressed during the parasite life cycle and discovered the mechanism by which this expression is controlled. Furthermore, we demonstrate that TCTP is important for cell growth as well as proper cell and organelle morphology in the insect form of the parasite.\n\n2. AbstractTCTP is a highly conserved protein ubiquitously expressed in eukaryotes. Studies have reported TCTP to be involved in growth and development, cell cycle progression, protection against cellular stresses and apoptosis, indicating the multifunctional role of the protein. Here, for the first time we characterize the expression and function of TCTP in the unicellular parasite Trypanosoma brucei. We identified two paralogue TCTP genes, which we named TbTCTP1 and TbTCTP2. They have identical 5UTRs and only ten single nucleotide polymorphisms in the open reading frames (ORFs). However, the 3UTRs differ dramatically in sequence and length. We found that the two TCTP mRNAs are differentially expressed during T. brucei life cycle. While procyclic form trypanosomes (PCF) express TCTP1, the bloodstream form trypanosomes (BSF), express TCTP2. We link the differential expression to the distinct 3UTRs of the paralogues. In PCF cells, the protein appears to localize in the cytosol. We show that TCTP1 is essential for normal cell growth and has pleiotropic effects on the cells including aberrant cell morphology, enlarged and reduced number of acidocalcisomes and appearance of accumulations in the mitochondria.

microbiology↗