PubMed · 14958086
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F P DE FIGUEIREDO. 1952. [Pulmonary function tests].. https://pubmed.ncbi.nlm.nih.gov/14958086/
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A putative yeast mitochondrial upstream activating sequence (UAS) was used in a one-hybrid screening procedure that identified the YJR127C ORF on chromosome X. This gene was previously designated ZMS1 and is listed as a transcription factor on the SGD website. Real time RT-PCR assays showed that expression of YJR127C/ZMS1 was glucose-repressible, and a deletion mutant for the gene showed a growth defect on glycerol-based but not on glucose- or ethanol-based medium. Real time RT-PCR analyses identified severely attenuated transcript levels from GUT1 and GUT2 to be the source of that growth defect, the products of GUT1 and GUT2 are required for glycerol utilization. mRNA levels from a large group of mitochondria- and respiration-related nuclear genes also were shown to be attenuated in the deletion mutant. Importantly, transcript levels from the mitochondrial OLI1 gene, which has an associated organellar UAS, were attenuated in the DeltaYJR127C mutant during glycerol-based growth, but those from COX3 (OXI2), which lacks an associated mitochondrial UAS, were not. Transcriptome analysis of the glycerol-grown deletion mutant showed that genes in several metabolic and other categories are affected by loss of this gene product, including protein transport, signal transduction, and others. Thus, the product of YJR127C/ZMS1 is involved in transcriptional control for genes in both cellular genetic compartments, many of which specify products required for glycerol-based growth, respiration, and other functions.
Mitochondria have a single release factor that recognizes all stop codons in mRNAs. The yeast mitochondrial release factor, mRF1, is a protein of 43 kDa that emerges from its precursor by cleavage of a mitochondrial targeting sequence. mRF1 is localized exclusively in mitochondria, even when it is overproduced. A several-fold increase in mRF1 levels slightly inhibits the growth of wild-type cells on media containing a non-fermentable carbon source. A direct antisuppressor effect of overproduced mRF1 is observed, since the MRF1 gene on a multicopy plasmid causes Gly(-) phenotypes of the leaky mit(-) point mutations in mtDNA. We also examine steady-state mRF1 levels in a respiratory-deficient mrf1-780 mutant with inhibited mitochondrial translation. We show that both the mRF1 protein and the MRF1 transcript are elevated in mrf1-780 cells. A similar increase in mRF1 expression is observed in the rho(0) strain with no mitochondrial translation. This is indicative of retrograde signalling in the regulation of MRF1 expression. According to our hypothesis, inhibition of translation in the mrf1-780 strain is due to mitoribosome stalling at the stop codon and the observed elevated level of release factor is a secondary effect of respiratory deficiency.
In isolated potato tuber mitochondria, palmitic acid (PA) can induce a H+ leak inhibited by GTP in the phosphorylating (state 3) respiration but not in the resting (state 4) respiration. The PA-induced H+ leak is constant when state 3 respiration is decreased by an inhibition of the succinate uptake with n-butyl malonate (nBM). We show that the efficiency of inhibition by GTP is decreased when state 3 respiration is progressively inhibited by antimycin A (AA) and is restored following subsequent addition of nBM. We propose that in phosphorylating potato tuber mitochondria, the redox state of ubiquinone, which can antagonistically be varied with AA and nBM, modulates inhibition of the PA-activated UCP-sustained H+ leak by GTP.