A PPR protein in the PLS subfamily stabilizes the 5'-end of processed rpl16 mRNAs in maize chloroplasts.
Pentatricopeptide repeat (PPR) proteins are a large family of helical-repeat proteins that bind RNA in mitochondria and chloroplasts. Precise RNA targets and functions have been assigned to only a small fraction of the >400 members of the PPR family in plants. We used the amino acid code governing the specificity of RNA binding by PPR repeats to infer candidate-binding sites for the maize protein PPR103 and its ortholog Arabidopsis EMB175. Genetic and biochemical data confirmed a predicted binding site in the chloroplast rpl16 5'UTR to be a site of PPR103 action. This site maps to the 5' end of transcripts that fail to accumulate in ppr103 mutants. A small RNA corresponding to the predicted PPR103 binding site accumulates in a PPR103-dependent fashion, as expected of PPR103's in vivo footprint. Recombinant PPR103 bound specifically to this sequence in vitro These observations imply that PPR103 stabilizes rpl16 mRNA by impeding 5'→3' RNA degradation. Previously described PPR proteins with this type of function consist of canonical PPR motifs. By contrast, PPR103 is a PLS-type protein, an architecture typically associated with proteins that specify sites of RNA editing. However, PPR103 is not required to specify editing sites in chloroplasts.
Centre National de la Recherche Scientifique (CNRS), Institut de Biologie Moléculaire des Plantes, 12 rue du Général Zimmer, 67084 Strasbourg, France kamel.hammani@ibmp-cnrs.unistra.fr.
Kamel
K
Hammani
Molekulare Botanik, Universität Ulm, 89069 Ulm, Germany.
Mizuki
M
Takenaka
Institute of Molecular Biology, University of Oregon, Eugene, OR 97403, USA.
Rafael
R
Miranda
Institute of Molecular Biology, University of Oregon, Eugene, OR 97403, USA.
Alice
A
Barkan
D020121:5' Untranslated Regions; D000595:Amino Acid Sequence; D001483:Base Sequence; D002736:Chloroplasts / Q000235:genetics* / Q000378:metabolism; D010940:Plant Proteins / Q000502:physiology*; D011485:Protein Binding; D017393:RNA Editing; D020871:RNA Stability; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism*; D018749:RNA, Plant / Q000235:genetics / Q000378:metabolism; D016601:RNA-Binding Proteins / Q000502:physiology*; D012270:Ribosomes / Q000378:metabolism; D003313:Zea mays / Q000235:genetics* / Q000378:metabolism
D020121:5' Untranslated Regions; D010940:Plant Proteins; D012333:RNA, Messenger; D018749:RNA, Plant; D016601:RNA-Binding Proteins