Tissue-specific decrease of translation in aged mouse mitochondria: Relation with transcript and deletion level

Abstract

In vitro translation of cytochrome c oxidase on mitochondria of mouse tissues was compared with the level of mitochondrial DNA (mtDNA) deletion and of the transcript during aging. Translation activity of mitochondria from old testis declined considerably compared with old brain and liver. In the region of 12S rRNA and URF6L spanning COXIII gene locus, age-related mtDNA deletion was considerable and multiple ranging from 7.4 kb to 9.17 kb deletion in old brain and testis, but barely detectable in old liver. The transcript amount of subunit III of cytochrome c oxidase decreased substantially in old testis, while being little reduced in brain and liver. Deletion, transcription and translation levels seemed to be related to testis during aging but not in brain. Especially deletion level was not related with age in brain and liver. Present observation from testis suggests that, among the gene mutation and gene expression steps, translational alteration may play a major role in irreversible aging process.