Dataset Information

LRPPRC/SLIRP suppresses PNPase-mediated mRNA decay and promotes polyadenylation in human mitochondria.

ABSTRACT: 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.

SUBMITTER: Chujo T

PROVIDER: S-EPMC3439899 | biostudies-other | 2012 Sep

REPOSITORIES: biostudies-other

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LRPPRC/SLIRP suppresses PNPase-mediated mRNA decay and promotes polyadenylation in human mitochondria.

Chujo Takeshi T Ohira Takayuki T Sakaguchi Yuriko Y Goshima Naoki N Nomura Nobuo N Nagao Asuteka A Suzuki Tsutomu T

Nucleic acids research 20120531 16

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 me ...[more]

PMID: 22661577

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Project description:Nonsense-mediated decay (NMD) is an mRNA surveillance pathway that selectively recognizes and degrades defective mRNAs carrying premature translation-termination codons. However, several studies have shown that NMD also targets physiological transcripts that encode full-length proteins, modulating their expression. Indeed, some features of physiological mRNAs can render them NMD-sensitive. Human HFE is a MHC class I protein mainly expressed in the liver that, when mutated, can cause hereditary hemochromatosis, a common genetic disorder of iron metabolism. The HFE gene structure comprises seven exons; although the sixth exon is 1056 base pairs (bp) long, only the first 41 bp encode for amino acids. Thus, the remaining downstream 1015 bp sequence corresponds to the HFE 3' untranslated region (UTR), along with exon seven. Therefore, this 3' UTR encompasses an exon/exon junction, a feature that can make the corresponding physiological transcript NMD-sensitive. Here, we demonstrate that in UPF1-depleted or in cycloheximide-treated HeLa and HepG2 cells the HFE transcripts are clearly upregulated, meaning that the physiological HFE mRNA is in fact an NMD-target. This role of NMD in controlling the HFE expression levels was further confirmed in HeLa cells transiently expressing the HFE human gene. Besides, we show, by 3'-RACE analysis in several human tissues that HFE mRNA expression results from alternative cleavage and polyadenylation at four different sites--two were previously described and two are novel polyadenylation sites: one located at exon six, which confers NMD-resistance to the corresponding transcripts, and another located at exon seven. In addition, we show that the amount of HFE mRNA isoforms resulting from cleavage and polyadenylation at exon seven, although present in both cell lines, is higher in HepG2 cells. These results reveal that NMD and alternative polyadenylation may act coordinately to control HFE mRNA levels, possibly varying its protein expression according to the physiological cellular requirements.

Dataset Information

LRPPRC/SLIRP suppresses PNPase-mediated mRNA decay and promotes polyadenylation in human mitochondria.

Publications

LRPPRC/SLIRP suppresses PNPase-mediated mRNA decay and promotes polyadenylation in human mitochondria.

Similar Datasets

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