The pentatricopeptide repeat-SMR protein ATP4 promotes translation of the chloroplast atpB/E mRNA.
The regulation of chloroplast translation by nuclear gene products makes a major contribution to the control of chloroplast gene expression, but the underlying mechanisms are poorly understood. We describe a pentatricopeptide repeat (PPR) protein in maize, ATP4, that is necessary for translation of the chloroplast atpB open reading frame. We demonstrate that ATP4 associates in vivo with sequences near the 5' end of the unusually long 5' UTR of the atpB/E mRNA, that it facilitates ribosome association with this mRNA, and that it is required for accumulation and activity of the chloroplast ATP synthase. ATP4 is multifunctional, in that it also enhances atpA translation and is required for accumulation of specific processed atpF and psaJ transcripts. ATP4 belongs to a sub-class of PPR proteins that include a small MutS-related (SMR) domain. SMR domains had previously been associated primarily with DNA-related functions, but our findings imply that at least some PPR-SMR proteins can act on RNA. ATP4 is orthologous to the Arabidopsis protein SVR7, but the phenotypes of atp4 and svr7 mutants suggest that the functions of these orthologs have not been strictly conserved.
Molekulare Genetik, Institut für Biologie, Humboldt-Universität zu Berlin, D-10115 Berlin, Germany.
Reimo
R
Zoschke
Tiffany
T
Kroeger
Susan
S
Belcher
Mark Aurel
MA
Schöttler
Alice
A
Barkan
Christian
C
Schmitz-Linneweber
D020121:5' Untranslated Regions; D000483:Alleles; D025222:Chloroplast Proton-Translocating ATPases / Q000235:genetics / Q000378:metabolism; D002736:Chloroplasts / Q000201:enzymology / Q000235:genetics / Q000378:metabolism*; D004789:Enzyme Activation; D018506:Gene Expression Regulation, Plant; D047468:Immunoprecipitation; D016366:Open Reading Frames; D010788:Photosynthesis; D010940:Plant Proteins / Q000235:genetics / Q000378:metabolism; D014176:Protein Biosynthesis; D017434:Protein Structure, Tertiary; D018747:RNA, Chloroplast / Q000235:genetics / Q000378:metabolism*; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism*; D018749:RNA, Plant / Q000235:genetics / Q000378:metabolism*; D020449:Repetitive Sequences, Amino Acid; D012270:Ribosomes / Q000235:genetics / Q000378:metabolism; D003313:Zea mays / Q000201:enzymology / Q000235:genetics / Q000378:metabolism*
D020121:5' Untranslated Regions; D010940:Plant Proteins; D018747:RNA, Chloroplast; D012333:RNA, Messenger; D018749:RNA, Plant; D025222:Chloroplast Proton-Translocating ATPases