Dataset Information

MRB3010 is a core component of the MRB1 complex that facilitates an early step of the kinetoplastid RNA editing process.

ABSTRACT: Gene expression in the mitochondria of the kinetoplastid parasite Trypanosoma brucei is regulated primarily post-transcriptionally at the stages of RNA processing, editing, and turnover. The mitochondrial RNA-binding complex 1 (MRB1) is a recently identified multiprotein complex containing components with distinct functions during different aspects of RNA metabolism, such as guide RNA (gRNA) and mRNA turnover, precursor transcript processing, and RNA editing. In this study we examined the function of the MRB1 protein, Tb927.5.3010, which we term MRB3010. We show that MRB3010 is essential for growth of both procyclic form and bloodstream form life-cycle stages of T. brucei. Down-regulation of MRB3010 by RNAi leads to a dramatic inhibition of RNA editing, yet its depletion does not impact total gRNA levels. Rather, it appears to affect the editing process at an early stage, as indicated by the accumulation of pre-edited and small partially edited RNAs. MRB3010 is present in large (>20S) complexes and exhibits both RNA-dependent and RNA-independent interactions with other MRB1 complex proteins. Comparison of proteins isolated with MRB3010 tagged at its endogenous locus to those reported from other MRB1 complex purifications strongly suggests the presence of an MRB1 "core" complex containing five to six proteins, including MRB3010. Together, these data further our understanding of the function and composition of the imprecisely defined MRB1 complex.

SUBMITTER: Ammerman ML

PROVIDER: S-EPMC3078736 | biostudies-literature | 2011 May

REPOSITORIES: biostudies-literature

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MRB3010 is a core component of the MRB1 complex that facilitates an early step of the kinetoplastid RNA editing process.

Ammerman Michelle L ML Hashimi Hassan H Novotná Lucie L Cicová Zdenka Z McEvoy Sarah M SM Lukes Julius J Read Laurie K LK

RNA (New York, N.Y.) 20110330 5

Gene expression in the mitochondria of the kinetoplastid parasite Trypanosoma brucei is regulated primarily post-transcriptionally at the stages of RNA processing, editing, and turnover. The mitochondrial RNA-binding complex 1 (MRB1) is a recently identified multiprotein complex containing components with distinct functions during different aspects of RNA metabolism, such as guide RNA (gRNA) and mRNA turnover, precursor transcript processing, and RNA editing. In this study we examined the functi ...[more]

PMID: 21451155

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Project description:Adaptation and survival of Trypanosoma brucei requires editing of mitochondrial mRNA by uridylate (U) insertion and deletion. Hundreds of small guide RNAs (gRNAs) direct the mRNA editing at over 3,000 sites. RNA editing is controlled during the life cycle but the regulation of substrate and stage specificity remains unknown. Editing progresses in the 3' to 5' direction along the pre-mRNA in blocks, each targeted by a unique gRNA. A critical editing factor is the mitochondrial RNA binding complex 1 (MRB1) that binds gRNA and transiently interacts with the catalytic RNA editing core complex (RECC). MRB1 is a large and dynamic complex that appears to be comprised of distinct but related subcomplexes (termed here MRBs). MRBs seem to share a 'core' complex of proteins but differ in the composition of the 'variable' proteins. Since some proteins associate transiently the MRBs remain imprecisely defined. MRB1 controls editing by unknown mechanisms, and the functional relevance of the different MRBs is unclear. We previously identified two distinct MRBs, and showed that they carry mRNAs that undergo editing. We proposed that editing takes place in the MRBs because MRBs stably associate with mRNA and gRNA but only transiently interact with RECC, which is RNA free. Here, we identify the first specialized functions in MRBs: 1) 3010-MRB is a major scaffold for RNA editing, and 2) REH2-MRB contains a critical trans-acting RNA helicase (REH2) that affects multiple steps of editing function in 3010-MRB. These trans effects of the REH2 include loading of unedited mRNA and editing in the first block and in subsequent blocks as editing progresses. REH2 binds its own MRB via RNA, and conserved domains in REH2 were critical for REH2 to associate with the RNA and protein components of its MRB. Importantly, REH2 associates with a ~30 kDa RNA-binding protein in a novel ~15S subcomplex in RNA-depleted mitochondria. We use these new results to update our model of MRB function and organization.

Dataset Information

MRB3010 is a core component of the MRB1 complex that facilitates an early step of the kinetoplastid RNA editing process.

Publications

MRB3010 is a core component of the MRB1 complex that facilitates an early step of the kinetoplastid RNA editing process.

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