3 research outputs found

    Native Variants of the MRB1 Complex Exhibit Specialized Functions in Kinetoplastid RNA Editing

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    We want to thank Kathy Kyler for editing this manuscript, Ken Stuart for supplying monoclonal antisera against RECC subunits, and Laurie K. Read for her gift of polyclonal antisera against GAP1 and RGG2. Funding: National Science Foundation Grant No. NSF1122109 (PI: J.Cruz-Reyes.). NIH/National Institute of Allergies and Infectious Diseases R01 AI088011 (PI: Blaine Mooers). Institutional Development Award (IDeA) from the National Institute of General Medical Sciences of the National Institutes of Health under grant number P20 GM103640. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.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.Yeshttp://www.plosone.org/static/editorial#pee

    Many Central American hummingbirds can be aged and sexed by molt patterns and bill corrugations

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    We document molt extent; age-specific molt patterns, plumages, and percent of the bill with corrugations; the presence or absence of delayed plumage maturation and bill color changes in males of some species; and molt timing in the 19 resident hummingbird species of Belize. Molt strategies and rates of bill smoothing were similar to North American species, with all species showing limited to partial preformative molts, replacing only body feathers and some wing coverts and retaining all remiges and rectrices. Extent of bill corrugations reduced to ≤10% of bill length in all species by the time definitive cycle basic plumage is achieved. Males in sexually dichromatic species showed delayed maturation in plumage characteristics and/or bill coloration, and in two dichromatic species some older females showed male-like plumage. Nine species representing multiple clades showed advanced timing to the second prebasic molt, indicating that this trait may be a proximal response to individuals not breeding during the first molt cycle. Species with advanced second prebasic molts replaced fewer wing coverts during the preformative molt than species with later molt timing