An upstream open reading frame and the context of the two AUG codons affect the abundance of mitochondrial and nuclear RNase H1.

TitleAn upstream open reading frame and the context of the two AUG codons affect the abundance of mitochondrial and nuclear RNase H1.
Publication TypeJournal Article
Year of Publication2010
AuthorsSuzuki, Y, J Holmes, B, Cerritelli, SM, Sakhuja, K, Minczuk, MA, Holt, IJ, Crouch, RJ
JournalMol Cell Biol
Volume30
Issue21
Pagination5123-34
Date Published2010 Nov
ISSN1098-5549
KeywordsAmino Acid Sequence, Animals, Base Sequence, Cell Line, Cell Nucleus, Codon, DNA, Mitochondrial, Humans, In Vitro Techniques, Isoenzymes, Liver, Mice, Mitochondria, Models, Biological, Molecular Sequence Data, Open Reading Frames, Peptide Chain Initiation, Translational, Protein Structure, Tertiary, Recombinant Proteins, Ribonuclease H, RNA, Messenger, Sequence Homology, Amino Acid
Abstract

RNase H1 in mammalian cells is present in nuclei and mitochondria. Its absence in mitochondria results in embryonic lethality due to the failure to amplify mitochondrial DNA (mtDNA). Dual localization to mitochondria and nuclei results from differential translation initiation at two in-frame AUGs (M1 and M27) of a single mRNA. Here we show that expression levels of the two isoforms depend on the efficiency of translation initiation at each AUG codon and on the presence of a short upstream open reading frame (uORF) resulting in the mitochondrial isoform being about 10% as abundant as the nuclear form. Translation initiation at the M1 AUG is restricted by the uORF, while expression of the nuclear isoform requires reinitiation of ribosomes at the M27 AUG after termination of uORF translation or new initiation by ribosomes skipping the uORF and the M1 AUG. Such translational organization of RNase H1 allows tight control of expression of RNase H1 in mitochondria, where its excess or absence can lead to cell death, without affecting the expression of the nuclear RNase H1.

DOI10.1128/MCB.00619-10
Alternate JournalMol. Cell. Biol.
Citation Key10.1128/MCB.00619-10
PubMed ID20823270
PubMed Central IDPMC2953059
Grant ListBB/F012802/1 / / Biotechnology and Biological Sciences Research Council / United Kingdom
MC_U105663140 / / Medical Research Council / United Kingdom
MC_U105697135 / / Medical Research Council / United Kingdom
/ / Medical Research Council / United Kingdom