LRPPRC/SLIRP suppresses PNPase-mediated mRNA decay and promotes polyadenylation in human mitochondria.
In human mitochondria, 10 mRNAs species are generated from a long polycistronic precursor that is transcribed from the heavy chain of mitochondrial DNA, in theory yielding equal copy numbers of mRNA molecules. However, the steady-state levels of these mRNAs differ substantially. Through absolute quantification of mRNAs in HeLa cells, we show that the copy numbers of all mitochondrial mRNA species range from 6000 to 51,000 molecules per cell, indicating that mitochondria actively regulate mRNA metabolism. In addition, the copy numbers of mitochondrial mRNAs correlated with their cellular half-life. Previously, mRNAs with longer half-lives were shown to be stabilized by the LRPPRC/SLIRP complex, which we find that cotranscriptionally binds to coding sequences of mRNAs. We observed that the LRPPRC/SLIRP complex suppressed 3' exonucleolytic mRNA degradation mediated by PNPase and SUV3. Moreover, LRPPRC promoted the polyadenylation of mRNAs mediated by mitochondrial poly(A) polymerase (MTPAP) in vitro. These findings provide a framework for understanding the molecular mechanism of mRNA metabolism in human mitochondria.
Department of Chemistry and Biotechnology, Graduate School of Engineering, University of Tokyo, Tokyo, Japan.
Takeshi
T
Chujo
Takayuki
T
Ohira
Yuriko
Y
Sakaguchi
Naoki
N
Goshima
Nobuo
N
Nomura
Asuteka
A
Nagao
Tsutomu
T
Suzuki
D053487:DEAD-box RNA Helicases / Q000378:metabolism; D012321:DNA-Directed RNA Polymerases / Q000378:metabolism; D006367:HeLa Cells; D006801:Humans; D008928:Mitochondria / Q000201:enzymology / Q000235:genetics; D024101:Mitochondrial Proteins / Q000378:metabolism; D009363:Neoplasm Proteins / Q000378:metabolism*; D026723:Polyadenylation; D011117:Polyribonucleotide Nucleotidyltransferase / Q000037:antagonists & inhibitors / Q000378:metabolism*; D012313:RNA / Q000032:analysis / Q000737:chemistry / Q000378:metabolism*; D012322:RNA Precursors / Q000378:metabolism; D020871:RNA Stability; D012333:RNA, Messenger / Q000032:analysis / Q000737:chemistry / Q000378:metabolism*; D000077278:RNA, Mitochondrial; D016601:RNA-Binding Proteins / Q000378:metabolism*
C087940:LRPPRC protein, human; D024101:Mitochondrial Proteins; D009363:Neoplasm Proteins; D012322:RNA Precursors; D012333:RNA, Messenger; D000077278:RNA, Mitochondrial; D016601:RNA-Binding Proteins; C512286:SLIRP protein, human; D012313:RNA; D012321:DNA-Directed RNA Polymerases; C555258:MTPAP protein, human; D011117:Polyribonucleotide Nucleotidyltransferase; C469673:SUPV3L1 protein, human; D053487:DEAD-box RNA Helicases