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Oxygen tension regulates mitochondrial DNA-encoded complex I gene expression.
José I Piruat1, José López-Barneo
1Laboratorio de Investigaciones Biomédicas, Departamento de Fisiología, Seville, Spain.
The Journal of Biological Chemistry
|November 1, 2005
Summary
Hypoxia specifically down-regulates mitochondrial complex I gene expression in rat cells. This rapid, iron-dependent process affects mRNA stability and may adjust cell respiration during oxygen changes.
Area of Science:
- Cellular Biology
- Mitochondrial Biology
- Gene Expression Regulation
Background:
- Oxygen is a key regulator of nuclear gene expression.
- Mitochondria consume most cellular oxygen, but their genome's response to oxygen levels is poorly understood.
Purpose of the Study:
- To investigate how oxygen tension influences the expression of mitochondrial DNA (mtDNA)-encoded genes.
- To identify specific mtDNA genes regulated by hypoxia and elucidate the underlying mechanisms.
Main Methods:
- Utilized O2-sensitive rat PC12 cells.
- Analyzed mRNA levels of mtDNA-encoded genes under varying oxygen tensions.
- Assessed mitochondrial complex I activity and the effect of iron chelation.
Main Results:
- Hypoxia specifically down-regulated transcripts for mitochondrial complex I NADH dehydrogenase (ND) subunits, including ND4 and ND5 mRNAs.
- A stable mRNA precursor containing ND5 and cytochrome b genes was also down-regulated.
- The effect was rapid (<30 min), reversible, occurred at moderate hypoxia (20-70 mm Hg), and was paralleled by reduced complex I activity.
- Iron chelation retarded the down-regulation, suggesting an iron-dependent post-transcriptional mechanism.
Conclusions:
- Hypoxia induces a rapid, specific down-regulation of mitochondrial complex I gene expression.
- An iron-dependent post-transcriptional mechanism likely regulates mitochondrial mRNA stability under hypoxia.
- This regulation may be an adaptive mechanism to adjust cellular respiration rates in response to oxygen availability.