Muller EA, Danner DJ. Tissue-specific translation of murine branched-chain alpha-ketoacid dehydrogenase kinase mRNA is dependent upon an upstream open reading frame in the 5'-untranslated region.
J Biol Chem 2004;
279:44645-55. [PMID:
15302860 DOI:
10.1074/jbc.m406550200]
[Citation(s) in RCA: 16] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The committed step in the pathway for leucine, isoleucine, and valine catabolism is catalyzed by branched-chain alpha-ketoacid dehydrogenase (BCKD). This multienzyme complex is itself regulated through reversible subunit phosphorylation by a specific kinase (BCKD-kinase). Although BCKD is present in the mitochondria of all mammalian cells, BCKD-kinase has a tissue-specific pattern of expression. Various experimental, nutritional, and hormonal conditions have been used to alter the expression of BCKD-kinase, yet little is known regarding the regulation of basal BCKD-kinase expression under normal conditions including the mechanism of its tissue specificity in any organism. Here we use tissue-derived cultured cells to explore the mechanisms used to control BCKD-kinase expression. Whereas the amount of BCKD-kinase protein is significantly higher in mitochondria from C2C12 myotubes than in BNL Cl.2 liver cells, gene transcription and stability of BCKD-kinase mRNA share similar properties in these two cell types. Our results show that the amount of protein synthesized is regulated at the level of translation of BCKD-kinase mRNA and that an upstream open reading frame in the 5'-untranslated region of this transcript controls its translation. The location and putative 19-residue peptide are conserved in the mouse, rat, chimpanzee, and human genes. Likewise, gene structure of mouse, chimpanzee, and human BCKD-kinase is conserved, whereas the rat gene has lost intron 9.
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