Two CRM protein subfamilies cooperate in the splicing of group IIB introns in chloroplasts

Chloroplast genomes in angiosperms encode approximately 20 group II introns, approximately half of which are classified as subgroup IIB. The splicing of all but one of the subgroup IIB introns requires a heterodimer containing the peptidyl-tRNA hydrolase homolog CRS2 and one of two closely related p...

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Bibliographic Details
Published in:RNA (Cambridge) 2008-11, Vol.14 (11), p.2319-2332
Main Authors: Asakura, Yukari, Bayraktar, Omer Ali, Barkan, Alice
Format: Article
Language:English
Subjects:
Arabidopsis - genetics
Arabidopsis - growth & development
Arabidopsis - metabolism
Arabidopsis Proteins - classification
Arabidopsis Proteins - genetics
Arabidopsis Proteins - metabolism
Chloroplasts - genetics
Chloroplasts - metabolism
Introns
Mitochondria
NADH Dehydrogenase - genetics
Oryza - metabolism
Plant Proteins - classification
Plant Proteins - genetics
Plant Proteins - metabolism
RNA Splicing
Seeds - genetics
Seeds - growth & development
Seeds - metabolism
Zea mays - metabolism
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Summary:Chloroplast genomes in angiosperms encode approximately 20 group II introns, approximately half of which are classified as subgroup IIB. The splicing of all but one of the subgroup IIB introns requires a heterodimer containing the peptidyl-tRNA hydrolase homolog CRS2 and one of two closely related proteins, CAF1 or CAF2, that harbor a recently recognized RNA binding domain called the CRM domain. Two CRS2/CAF-dependent introns require, in addition, a CRM domain protein called CFM2 that is only distantly related to CAF1 and CAF2. Here, we show that CFM3, a close relative of CFM2, associates in vivo with those CRS2/CAF-dependent introns that are not CFM2 ligands. Mutant phenotypes in rice and Arabidopsis support a role for CFM3 in the splicing of most of the introns with which it associates. These results show that either CAF1 or CAF2 and either CFM2 or CFM3 simultaneously bind most chloroplast subgroup IIB introns in vivo, and that the CAF and CFM subunits play nonredundant roles in splicing. These results suggest that the expansion of the CRM protein family in plants resulted in two subfamilies that play different roles in group II intron splicing, with further diversification within a subfamily to accommodate multiple intron ligands.
ISSN:1355-8382
1469-9001
DOI:10.1261/rna.1223708