Oxygen and haem regulate the synthesis of peroxisomal proteins: catalase A, acyl-CoA oxidase and Pex1p in the yeast Saccharomyces cerevisiae; the regulation of these proteins by oxygen is not mediated by haem.
Saccharomyces cerevisiae genes related to respiration are typically controlled by oxygen and haem. Usually the regulation by these factors is co-ordinated; haem is indicated as the oxygen sensor. However, the responsiveness of peroxisome functions to these regulatory factors is poorly understood. The expression of CTA1, POX1 and PEX1 genes encoding the peroxisomal proteins catalase A, acyl-CoA oxidase and Pex1p peroxin respectively was studied under various conditions: in anaerobiosis, in the absence of haem and in respiratory incompetence caused by the lack of a mitochondrial genome (rho(0)). The influence of haem deficiency or rho(0) on peroxisomal morphology was also investigated. Respiratory incompetence has no effect on the expression of CTA1 and POX1, whereas in the absence of haem their expression is markedly decreased. The synthesis of Pex1p is decreased in rho(0) cells and is decreased even more in haem-deficient cells. Nevertheless, peroxisomal morphology in both these types of cell does not differ significantly from the morphology of peroxisomes in wild-type cells. The down-regulating effect of anoxia on the expression of CTA1 and POX1 is even stronger than the effect of haem deficiency and is not reversed by the addition of exogenous haem or the presence of endogenous haem. Moreover, neither of these genes responds to the known haem-controlled transcriptional factor Hap1p. In contrast with the other two genes studied, PEX1 is up-regulated in anaerobiosis. The existence of one or more novel mechanisms of regulation of peroxisomal genes by haem and oxygen, different from those already known in S. cerevisiae, is postulated.
Department of Genetics, Institute of Biochemistry and Biophysics Polish Academy of Sciences, Pawinskiego 5A, 02-106 Warszawa, Poland.
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Rytka
D000074183:ATPases Associated with Diverse Cellular Activities; D042962:Acyl-CoA Oxidase; D000251:Adenosine Triphosphatases; D002374:Catalase / Q000096:biosynthesis*; D005656:Fungal Proteins / Q000096:biosynthesis*; D015966:Gene Expression Regulation, Fungal; D005800:Genes, Fungal; D006023:Glycoproteins / Q000096:biosynthesis*; D006418:Heme / Q000378:metabolism*; D008565:Membrane Proteins; D010088:Oxidoreductases / Q000096:biosynthesis*; D010100:Oxygen / Q000378:metabolism*; D020675:Peroxisomes / Q000378:metabolism*; D012441:Saccharomyces cerevisiae / Q000201:enzymology / Q000378:metabolism*; D029701:Saccharomyces cerevisiae Proteins
D005656:Fungal Proteins; D006023:Glycoproteins; D008565:Membrane Proteins; D029701:Saccharomyces cerevisiae Proteins; D006418:Heme; D010088:Oxidoreductases; D002374:Catalase; D042962:Acyl-CoA Oxidase; C467991:POX1 protein, S cerevisiae; D000251:Adenosine Triphosphatases; D000074183:ATPases Associated with Diverse Cellular Activities; C511586:PEX1 protein, S cerevisiae; C111808:PEX1 protein, human; D010100:Oxygen