Ribonuclease III Domain Protein Functions in Group II Intron Splicing in Maize Chloroplasts
Chloroplast genomes in land plants harbor ~20 group II introns. Genetic approaches have identified proteins involved in the splicing of many of these introns, but the proteins identified to date cannot account for the large size of intron ribonucleoprotein complexes and are not sufficient to reconst...
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Published in | The Plant cell Vol. 19; no. 8; pp. 2606 - 2623 |
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Main Authors | , , , , , , , |
Format | Journal Article |
Language | English |
Published |
United States
American Society of Plant Biologists
01.08.2007
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Subjects | |
Online Access | Get full text |
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Summary: | Chloroplast genomes in land plants harbor ~20 group II introns. Genetic approaches have identified proteins involved in the splicing of many of these introns, but the proteins identified to date cannot account for the large size of intron ribonucleoprotein complexes and are not sufficient to reconstitute splicing in vitro. Here, we describe an additional protein that promotes chloroplast group II intron splicing in vivo. This protein, RNC1, was identified by mass spectrometry analysis of maize (Zea mays) proteins that coimmunoprecipitate with two previously identified chloroplast splicing factors, CAF1 and CAF2. RNC1 is a plant-specific protein that contains two ribonuclease III (RNase III) domains, the domain that harbors the active site of RNase III and Dicer enzymes. However, several amino acids that are essential for catalysis by RNase III and Dicer are missing from the RNase III domains in RNC1. RNC1 is found in complexes with a subset of chloroplast group II introns that includes but is not limited to CAF1- and CAF2-dependent introns. The splicing of many of the introns with which it associates is disrupted in maize rnc1 insertion mutants, indicating that RNC1 facilitates splicing in vivo. Recombinant RNC1 binds both single-stranded and double-stranded RNA with no discernible sequence specificity and lacks endonuclease activity. These results suggest that RNC1 is recruited to specific introns via protein-protein interactions and that its role in splicing involves RNA binding but not RNA cleavage activity. |
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Bibliography: | http://www.plantcell.org/ ObjectType-Article-1 SourceType-Scholarly Journals-1 ObjectType-Feature-2 content type line 23 Address correspondence to abarkan@uoregon.edu. The author responsible for distribution of materials integral to the findings presented in this article in accordance with the policy described in the Instructions for Authors (www.plantcell.org) is: Alice Barkan (abarkan@uoregon.edu). These authors contributed equally to this work. Online version contains Web-only data. www.plantcell.org/cgi/doi/10.1105/tpc.107.053736 Current address: Cellular and Molecular Biology Graduate Program, University of Wisconsin, Madison, WI 53706. |
ISSN: | 1040-4651 1532-298X 1532-298X |
DOI: | 10.1105/tpc.107.053736 |