Mutations in the Gene Encoding C8orf38 Block Complex I Assembly by Inhibiting Production of the Mitochondria-Encoded Subunit ND1

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• 作者：Matthew McKenzie¹ ; Elena J. Tucker² ;   ; ³ ; Alison G. Compton² ; Michael Lazarou⁴ ;   ; ⁵ ; Christa George⁵ ; David R. Thorburn² ;   ; ³ ; Michael T. Ryan⁵ ;   ; ⁶ ;   ; ^{M.Ryan@latrobe.edu.au}
• 关键词：mitochondria ; complex I assembly factor ; Leigh syndrome ; blue native-PAGE ; mtDNA-encoded translation
• 刊名：Journal of Molecular Biology
• 出版年：2011
• 出版时间：2 December 2011
• 年：2011
• 卷：414
• 期：3
• 页码：413-426
• 全文大小：1161 K

文摘

The assembly of complex I (NADH¨Cubiquinone oxidoreductase) is a complicated process, requiring the integration of 45 subunits encoded by both nuclear and mitochondrial DNAs into a structure of approximately 1?MDa. A number of ¡°assembly factors?that aid complex I biogenesis have recently been described, including C8orf38. This protein was identified as an assembly factor by its evolutionary conservation in organisms containing complex I and by a C8orf38 mutation in a patient presenting with Leigh syndrome and isolated complex I deficiency. In this report, we have undertaken the characterization of C8orf38 and its role in complex I assembly. Analysis of mitochondria from fibroblasts of a patient harboring a C8orf38 mutation showed almost undetectable levels of steady-state complex I and defective biogenesis of the mtDNA-encoded subunit ND1. Complementation with wild-type C8orf38 restored the levels of both ND1 and complex I, confirming the C8orf38 mutation as the cause of the complex I defect in the patient. In the absence of ND1 in patient cells, early- and mid-stage intermediate complexes were still formed; however, assembly of late-stage intermediates was impaired, indicating a convergence point in the assembly process. While C8orf38 appears to behave at a step in complex I biogenesis similar to that of the assembly factor C20orf7, complementation studies showed that both proteins are required for ND1 synthesis/stabilization. We conclude that C8orf38 is a crucial factor required for the translation and/or integration of ND1 into an early-stage assembly intermediate and that mutation of C8orf38 disrupts the initial stages of complex I biogenesis.