Rpm2, the Protein Subunit of Mitochondrial RNase P in Saccharomyces cerevisiae, Also Has a Role in the Translation of Mitochondrially Encoded Subunits of Cytochrome c Oxidase

Genetics ◽  
2001 ◽  
Vol 158 (2) ◽  
pp. 573-585
Author(s):  
Vilius Stribinskis ◽  
Guo-Jian Gao ◽  
Steven R Ellis ◽  
Nancy C Martin
Keyword(s):  
Saccharomyces Cerevisiae ◽  
Cytochrome C ◽  
Cytochrome C Oxidase ◽  
Mitochondrial Biogenesis ◽  
Mitochondrial Protein ◽  
Nuclear Gene ◽  
Rnase P ◽  
Wild Type ◽  
Protein Subunit ◽  
Mitochondrial Translation

Abstract RPM2 is a Saccharomyces cerevisiae nuclear gene that encodes the protein subunit of mitochondrial RNase P and has an unknown function essential for fermentative growth. Cells lacking mitochondrial RNase P cannot respire and accumulate lesions in their mitochondrial DNA. The effects of a new RPM2 allele, rpm2-100, reveal a novel function of RPM2 in mitochondrial biogenesis. Cells with rpm2-100 as their only source of Rpm2p have correctly processed mitochondrial tRNAs but are still respiratory deficient. Mitochondrial mRNA and rRNA levels are reduced in rpm2-100 cells compared to wild type. The general reduction in mRNA is not reflected in a similar reduction in mitochondrial protein synthesis. Incorporation of labeled precursors into mitochondrially encoded Atp6, Atp8, Atp9, and Cytb protein was enhanced in the mutant relative to wild type, while incorporation into Cox1p, Cox2p, Cox3p, and Var1p was reduced. Pulse-chase analysis of mitochondrial translation revealed decreased rates of translation of COX1, COX2, and COX3 mRNAs. This decrease leads to low steady-state levels of Cox1p, Cox2p, and Cox3p, loss of visible spectra of aa3 cytochromes, and low cytochrome c oxidase activity in mutant mitochondria. Thus, RPM2 has a previously unrecognized role in mitochondrial biogenesis, in addition to its role as a subunit of mitochondrial RNase P. Moreover, there is a synthetic lethal interaction between the disruption of this novel respiratory function and the loss of wild-type mtDNA. This synthetic interaction explains why a complete deletion of RPM2 is lethal.

scholarly journals Yeast mitochondrial RNase P RNA synthesis is altered in an RNase P protein subunit mutant: insights into the biogenesis of a mitochondrial RNA-processing enzyme.

1996 ◽  
Vol 16 (7) ◽  
pp. 3429-3436 ◽  
Author(s):  
V Stribinskis ◽  
G J Gao ◽  
P Sulo ◽  
Y L Dang ◽  
N C Martin
Keyword(s):  
Rna Processing ◽  
Mitochondrial Protein ◽  
Rnase P ◽  
Mitochondrial Rna ◽  
Wild Type ◽  
Protein Subunit ◽  
Mitochondrial Trna ◽  
P Deficiency ◽  
F Gene ◽  
P Protein

Rpm2p is a protein subunit of Saccharomyces cerevisiae yeast mitochondrial RNase P, an enzyme which removes 5' leader sequences from mitochondrial tRNA precursors. Precursor tRNAs accumulate in strains carrying a disrupted allele of RPM2. The resulting defect in mitochondrial protein synthesis causes petite mutants to form. We report here that alteration in the biogenesis of Rpm1r, the RNase P RNA subunit, is another consequence of disrupting RPM2. High-molecular-weight transcripts accumulate, and no mature Rpm1r is produced. Transcript mapping reveals that the smallest RNA accumulated is extended on both the 5' and 3' ends relative to mature Rpm1r. This intermediate and other longer transcripts which accumulate are also found as low-abundance RNAs in wild-type cells, allowing identification of processing events necessary for conversion of the primary transcript to final products. Our data demonstrate directly that Rpm1r is transcribed with its substrates, tRNA met f and tRNAPro, from a promoter located upstream of the tRNA met f gene and suggest that a portion also originates from a second promoter, located between the tRNA met f gene and RPM1. We tested the possibility that precursors accumulate because the RNase P deficiency prevents the removal of the downstream tRNAPro. Large RPM1 transcripts still accumulate in strains missing this tRNA. Thus, an inability to process cotranscribed tRNAs does not explain the precursor accumulation phenotype. Furthermore, strains with mutant RPM1 genes also accumulate precursor Rpm1r, suggesting that mutations in either gene can lead to similar biogenesis defects. Several models to explain precursor accumulation are presented.

scholarly journals Overexpression of a leaderless form of yeast cytochrome c oxidase subunit Va circumvents the requirement for a leader peptide in mitochondrial import.

1990 ◽  
Vol 10 (9) ◽  
pp. 4984-4986 ◽  
Author(s):  
L K Dircks ◽  
R O Poyton
Keyword(s):  
Saccharomyces Cerevisiae ◽  
Cytochrome C ◽  
Cytochrome C Oxidase ◽  
Mitochondrial Protein ◽  
Leader Peptide ◽  
Mitochondrial Import ◽  
Oxidase Subunit

Subunit Va of Saccharomyces cerevisiae cytochrome c oxidase is a nucleus-encoded mitochondrial protein that is derived from a precursor with a 20-residue leader peptide. We previously reported that this leader peptide is required for import of subunit Va into mitochondria in vivo (S. M. Glaser, C. E. Trueblood, L. K. Dircks, R. O. Poyton, and M. G. Cumsky, J. Cell. Biochem. 36:275-278, 1988). Here we show that overproduction of a leaderless form of subunit Va circumvents the leader peptide requirement for import into mitochondria in vivo.

Control of the Saccharomyces cerevisiae regulatory gene PET494: transcriptional repression by glucose and translational induction by oxygen

1989 ◽  
Vol 9 (2) ◽  
pp. 484-491
Author(s):  
D L Marykwas ◽  
T D Fox
Keyword(s):  
Saccharomyces Cerevisiae ◽  
Cytochrome C ◽  
Cytochrome C Oxidase ◽  
Transcriptional Repression ◽  
Regulatory Gene ◽  
Carbon Sources ◽  
Nuclear Gene ◽  
Mrna Levels ◽  
Diploid Strain ◽  
In Cells

The product of the Saccharomyces cerevisiae nuclear gene PET494 is required to promote the translation of the mitochondrial mRNA encoding cytochrome c oxidase subunit III (coxIII). The level of cytochrome c oxidase activity is affected by several different environmental conditions, which also influence coxIII expression. We have studied the regulation of PET494 to test whether the level of its expression might modulate coxIII translation in response to these conditions. A pet494::lacZ fusion was constructed and used to monitor PET494 expression. PET494 was regulated by oxygen availability: expression in a respiration-competent diploid strain grown anaerobically was one-fifth the level of expression in aerobically grown cells. However, since PET494 mRNA levels did not vary in response to oxygen deprivation, regulation by oxygen appears to occur at the translational level. This oxygen regulation was not mediated by heme, and PET494 expression was independent of the heme activator protein HAP2. The regulation of PET494 expression by carbon source was also examined. In cells grown on glucose-containing medium, PET494 was expressed at levels four- to sixfold lower than in cells grown on ethanol and glycerol. However, addition of ethanol to glucose-containing medium induced PET494 expression approximately twofold. PET494 transcript levels varied over a fourfold range in response to different carbon sources. The effects on PET494 expression of mutations in the SNF1, SNF2, SSN6, and HXK2 genes were also determined and found to be minimal.

scholarly journals PET111, a Saccharomyces cerevisiae Nuclear Gene Required for Translation of the Mitochondrial mRNA Encoding Cytochrome c Oxidase Subunit II

Genetics ◽  
1987 ◽  
Vol 115 (4) ◽  
pp. 637-647
Author(s):  
Candace G Poutre ◽  
Thomas D Fox
Keyword(s):  
Cytochrome C ◽  
Cytochrome C Oxidase ◽  
Mitochondrial Gene ◽  
Nuclear Gene ◽  
State Level ◽  
Mitochondrial Genes ◽  
Chimeric Proteins ◽  
Wild Type ◽  
Oxidase Subunit ◽  
A Site

ABSTRACT Mutations in the nuclear gene PET111 are recessive and specifically block accumulation of cytochrome c oxidase subunit II (coxII), the product of a mitochondrial gene. However, the coxII mRNA is present in pet111 mutants at a level approximately one-third that of wild type. The simplest explanation for this phenotype is that PET111 is required for translation of the coxII mRNA. The reduced steady-state level of this mRNA is probably a secondary effect, caused by increased degradation of the untranslated transcript. Mitochondrial suppressors of pet111, carried on rho- mtDNAs, bypass the requirement for PET111 in coxII translation. Three suppressors are fusions between the coxII structural gene and other mitochondrial genes, that encode chimeric proteins consisting of the N-terminal portions of other mitochondrially coded proteins fused to the coxII precursor protein. When present together with rho  + mtDNA in a heteroplasmic state, these suppressors allow coxII synthesis in pet111 mutants. Thus in wild type, the PET111 product, or something under its control, probably acts at a site coded in the proximal portion of the gene for coxII to promote translation of the mRNA. PET111 was isolated by molecular cloning and genetically mapped to a position approximately midway between rna1 and SUP8 on chromosome XIII.

scholarly journals Ischemia-reperfusion induces inhibition of mitochondrial protein synthesis and cytochrome c oxidase activity in rat hippocampus

2009 ◽  
pp. 127-138
Author(s):  
P Racay ◽  
Z Tatarková ◽  
A Drgová ◽  
P Kaplan ◽  
D Dobrota
Keyword(s):  
Protein Synthesis ◽  
Cytochrome C ◽  
Cytochrome C Oxidase ◽  
Brain Ischemia ◽  
Ischemia Reperfusion ◽  
Mitochondrial Protein ◽  
Neuronal Cell ◽  
Northern Hybridization ◽  
Mitochondrial Protein Synthesis ◽  
Mitochondrial Translation

Dysfunction of mitochondria induced by ischemia is considered to be a key event triggering neuronal cell death after brain ischemia. Here we report the effect of ischemia-reperfusion on mitochondrial protein synthesis and activity of cytochrome c oxidase (EC 1.9.3.1, COX). By performing 4-vessel occlusion model of global brain ischemia, we have observed that 15 min of global ischemia led to the inhibition of COX subunit I (COXI) synthesis to 56 % of control. After 1, 3 and 24 h of reperfusion, COXI synthesis was inhibited to 46, 50 and 72 % of control, respectively. Depressed synthesis of COXI was not a result of either diminished transcription of COXI gene or increased proteolytic degradation of COXI, since both Northern hybridization and Western blotting did not show significant changes in COXI mRNA and protein level. Thus, ischemiareperfusion affects directly mitochondrial translation machinery. In addition, ischemia in duration of 15 min and consequent 1, 3 and 24 h of reperfusion led to the inhibition of COX activity to 90.3, 80.3, 81.9 and 83.5 % of control, respectively. Based on our data, we suggest that inhibition of COX activity is rather caused by ischemia-induced modification of COX polypeptides than by inhibition of mitochondrial translation.

Overexpression of a leaderless form of yeast cytochrome c oxidase subunit Va circumvents the requirement for a leader peptide in mitochondrial import

1990 ◽  
Vol 10 (9) ◽  
pp. 4984-4986
Author(s):  
L K Dircks ◽  
R O Poyton
Keyword(s):  
Saccharomyces Cerevisiae ◽  
Cytochrome C ◽  
Cytochrome C Oxidase ◽  
Mitochondrial Protein ◽  
Leader Peptide ◽  
Mitochondrial Import ◽  
Oxidase Subunit

Subunit Va of Saccharomyces cerevisiae cytochrome c oxidase is a nucleus-encoded mitochondrial protein that is derived from a precursor with a 20-residue leader peptide. We previously reported that this leader peptide is required for import of subunit Va into mitochondria in vivo (S. M. Glaser, C. E. Trueblood, L. K. Dircks, R. O. Poyton, and M. G. Cumsky, J. Cell. Biochem. 36:275-278, 1988). Here we show that overproduction of a leaderless form of subunit Va circumvents the leader peptide requirement for import into mitochondria in vivo.

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