Positive and negative elements involved in the differential regulation by heme and oxygen of the HEM13 gene (coproporphyrinogen oxidase) in Saccharomyces cerevisiae

Abstract

The Saccharomyces cerevisiae HEM13 gene codes for coproporphyrinogen oxidase (CPO), an oxygen-requiring enzyme catalysing the sixth step of heme biosynthesis. Its transcription is increased 40-50-fold in response to oxygen- or heme-deficiency. We have analyzed CPO activity and HEM13 mRNA levels in a set of isogenic strains carrying single or double deletions of the CYP1 (HAP1), ROX1, SSN6, or TUP1 genes. The cells were grown in the presence or absence of oxygen and under heme-deficiency (hem1 delta background). Both Rox1p and Cyp1p partially repressed HEM13 in aerobic heme-sufficient cells, probably in an independent manner. In the absence of heme, Cyp1p activated HEM13 and strongly repressed ROX1, allowing de-repression of HEM13. Cyp1p had no effect on HEM13 expression in anaerobic cells. Deletions of SSN6 or TUP1 dramatically de-repressed HEM13 in aerobic cells. A series of deletions in the HEM13 promoter identified at least four regulatory regions that are required for HEM13 regulation. Two regions, containing motifs similar to the Rox1p consensus sequences, act as repression sites under aerobic growth. The two other sites act as activation sequences required for full induction under oxygen- or heme-deficiency. Taken together, these results suggest that induction of HEM13 occurs in part through relief of repression exerted by Rox1p and Cyp1p, and in part by activation mediated partly by Cyp1p under heme-deficiency and by unknown factors under oxygen-deficiency.

Insights on the Evolution of Metabolic Networks of Unicellular Translationally Biased Organisms from Transcriptomic Data and Sequence Analysis

“…The high transcription of enzymes involved in highly active pathways during fermentation (and possibly not during aerobic respiration) correlates particularly well with the high CAI value of these enzymes. This observation is supported also by the available transcriptomic data on seripauperine proteins (Holstege et al 1998;James et al 2003;Viswanathan et al 1994) and on Hem13 proteins (Amillet et al 1995).…”

“…It is an oxidase with oxygen as a substrate (Zitomer and Lowry 1992). It displays a quite high CAI value (0.47), compared to l = 0.16 and r = 0.12 for all S. cerevisiae genes, and it is highly translated under anaerobic conditions (Amillet et al 1995) but not otherwise. Several facultative aerobic organisms contain a second enzyme catalyzing the same reaction as Hem13 but where the role of oxygen is replaced by molybdenum cofactor and S-adenosylmethionine.…”

Systems Level Insights Into the Stress Response to UV Radiation in the Halophilic ArchaeonHalobacterium NRC-1

“…The Rosetta-predicted structure for VNG1562C matched a cytochrome c protein from Rhodospirllum molischianum (PDB: 2ccy). Finally, the Rosetta-predicted structure for VNG1564H matched the three-dimensional structure of the heme biosynthesis regulator Tup1 (PDB: 1erj; Amillet et al 1995). Given the similarity of the molecular structure of precorrin to porphyrin, the predicted structural homology of VNG1562H to 2ccy suggests VNG1562H binds a porphyrin or a precorrin-like molecule.…”

Aquisition, Mobilization and Utilization of Cellular Iron and Heme: Endless Findings and Growing Evidence of Tight Regulation

“…HAP-1p and HAP-2/3/4/5p contain a DNAbinding domain recognizing the promoter region of these genes and a heme-binding domain where six copies of consensus amino acid sequence K/RCPV (CP-motif) are present (Zhang et al 1998;Ogawa et al 2001). Yeast coproporphyrinogen oxidase, catalyzing the 6th step in the biosynthesis of heme, is the rate-limiting enzyme and also regulated by the HAP system (Amillet et al 1995).…”