title: The structural landscape of native editosomes in African trypanosomes.
abstract: The majority of mitochondrial pre-messenger RNAs in African trypanosomes are substrates of a U-nucleotide-specific insertion/deletion-type RNA editing reaction. The process converts nonfunctional pre-mRNAs into translation-competent molecules and can generate protein diversity by alternative editing. High molecular mass protein complexes termed editosomes catalyze the processing reaction. They stably interact with pre-edited mRNAs and small noncoding RNAs, known as guide RNAs (gRNAs), which act as templates in the reaction. Editosomes provide a molecular surface for the individual steps of the catalytic reaction cycle and although the protein inventory of the complexes has been studied in detail, a structural analysis of the processing machinery has only recently been accomplished. Electron microscopy in combination with single particle reconstruction techniques has shown that steady state isolates of editosomes contain ensembles of two classes of stable complexes with calculated apparent hydrodynamic sizes of 20S and 35-40S. 20S editosomes are free of substrate RNAs, whereas 35-40S editosomes are associated with endogenous mRNA and gRNA molecules. Both complexes are characterized by a diverse structural landscape, which include complexes that lack or possess defined subdomains. Here, we summarize the consensus models and structural landmarks of both complexes. We correlate structural features with functional characteristics and provide an outlook into dynamic aspects of the editing reaction cycle.
authors.affiliation: Department of Microbiology and Genetics, Darmstadt University of Technology, Darmstadt, Germany. goringer@hrzpub.tu-darmstadt.de
authors.forename: H Ulrich
authors.initials: HU
authors.lastname: Göringer
authors.forename: Venkata Subbaraju
authors.initials: VS
authors.lastname: Katari
authors.forename: Cordula
authors.initials: C
authors.lastname: Böhm
mesh_terms: D007891:Leishmania / Q000378:metabolism; D046529:Microscopy, Electron, Transmission; D008954:Models, Biological; D008958:Models, Molecular; D046912:Multiprotein Complexes / Q000737:chemistry / Q000378:metabolism / Q000648:ultrastructure; D015800:Protozoan Proteins / Q000737:chemistry / Q000378:metabolism / Q000648:ultrastructure; D017393:RNA Editing / Q000502:physiology*; D012322:RNA Precursors / Q000378:metabolism; D017394:RNA, Guide, Kinetoplastida / Q000378:metabolism; D016053:RNA, Protozoan / Q000378:metabolism*; D016601:RNA-Binding Proteins / Q000737:chemistry / Q000378:metabolism / Q000648:ultrastructure; D014346:Trypanosoma brucei brucei / Q000378:metabolism*
chemical_list: D046912:Multiprotein Complexes; D015800:Protozoan Proteins; D012322:RNA Precursors; D016053:RNA, Protozoan; D016601:RNA-Binding Proteins; D017394:RNA, Guide, Kinetoplastida