LRPPRC and SLIRP interact in a ribonucleoprotein complex that regulates posttranscriptional gene expression in mitochondria.
Mutations in LRPPRC are responsible for the French Canadian variant of Leigh syndrome (LSFC), a neurodegenerative disorder caused by a tissue-specific deficiency in cytochrome c oxidase (COX). To investigate the pathogenic mechanism of disease, we studied LRPPRC function in LSFC and control fibroblasts. The level of mutated LRPPRC is reduced in LSFC cells, and this results in decreased steady-state levels of most mitochondrial mRNAs, but not rRNAs or tRNAs, a phenotype that can be reproduced by siRNA-mediated knockdown of LRPPRC in control cells. Processing of the primary transcripts appears normal. The resultant defect in mitochondrial protein synthesis in LSFC cells disproportionately affects the COX subunits, leading to an isolated COX assembly defect. Further knockdown of LRPPRC produces a generalized assembly defect in all oxidative phosphorylation complexes containing mtDNA-encoded subunits, due to a severe decrease in all mitochondrial mRNAs. LRPPRC exists in a high-molecular-weight complex, and it coimmunoprecipitates with SLIRP, a stem-loop RNA-binding protein. Although this interaction does not depend on mitochondrial mRNA, both proteins show reduced stability in its absence. These results implicate LRPPRC in posttranscriptional mitochondrial gene expression as part of a ribonucleoprotein complex that regulates the stability and handling of mature mRNAs.
Sasarman
Florin
F
Department of Human Genetics, Montreal Neurological Institute, McGill University, Montreal, QC, H3A 2B4, Canada.
Brunel-Guitton
Catherine
C
Antonicka
Hana
H
Wai
Timothy
T
Shoubridge
Eric A
EA
D003576:Electron Transport Complex IV / Q000378:metabolism; D005347:Fibroblasts / Q000201:enzymology / Q000473:pathology; D005786:Gene Expression Regulation; D006801:Humans; D007700:Kinetics; D007888:Leigh Disease / Q000201:enzymology / Q000235:genetics / Q000473:pathology; D008928:Mitochondria / Q000235:genetics* / Q000473:pathology; D008970:Molecular Weight; D046912:Multiprotein Complexes / Q000378:metabolism; D050505:Mutant Proteins / Q000378:metabolism; D009363:Neoplasm Proteins / Q000378:metabolism*; D010085:Oxidative Phosphorylation; D011485:Protein Binding; D021381:Protein Transport; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D016601:RNA-Binding Proteins / Q000378:metabolism*; D012261:Ribonucleoproteins / Q000378:metabolism; D014158:Transcription, Genetic
C087940:LRPPRC protein, human; D046912:Multiprotein Complexes; D050505:Mutant Proteins; D009363:Neoplasm Proteins; D012333:RNA, Messenger; D016601:RNA-Binding Proteins; D012261:Ribonucleoproteins; C512286:SLIRP protein, human; D003576:Electron Transport Complex IV