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CYP1 (HAP1) is a determinant effector of alternative expression of heme-dependent transcribed genes in yeast
J Verdière1, M Gaisne, R Labbe-Bois
1Centre de génétique moléculaire du CNRS, l'Université Pierre et Marie Curie, Gif sur Yvette, France.
Insights
The yeast CYP1 (HAP1) gene regulates gene transcription based on heme and oxygen levels. It activates HEM13 and inhibits 14DM under anaerobic or heme-deficient conditions, with opposite effects in aerobic, heme-sufficient cells.
Area of Science:
- Molecular Biology
- Yeast Genetics
- Gene Regulation
Background:
- The Saccharomyces cerevisiae CYP1 (HAP1) gene product is implicated in heme-mediated gene activation.
- CYP1 protein features suggest a role in sensing cellular redox state.
- Investigating CYP1's function in anaerobic gene expression is crucial.
Purpose of the Study:
- To analyze the regulatory effects of CYP1 on HEM13 and 14DM gene transcription.
- To determine how heme and oxygen availability influence CYP1's regulatory activity.
- To elucidate CYP1's role as a cellular redox sensor.
Main Methods:
- Utilized isogenic Saccharomyces cerevisiae strains with varying CYP1 and heme levels.
- Grew strains under aerobic and anaerobic conditions.
- Analyzed HEM13 and 14DM gene transcript levels using Northern blot analysis.
Main Results:
- CYP1 activates HEM13 transcription and inhibits 14DM transcription in anaerobic and heme-deficient conditions.
- Opposite regulatory effects were observed in aerobic, heme-sufficient conditions.
- CYP1 exhibits both positive and negative regulatory roles depending on the target gene and cellular environment.
Conclusions:
- CYP1 functions as an efficient transcriptional activator, particularly in heme-depleted environments.
- CYP1's regulatory function is gene-specific and sensitive to heme and oxygen levels.
- The presence or absence of heme or oxygen reverses the direction of CYP1-dependent gene regulation.
Abstract:
The CYP1 (HAP1) gene of Saccharomyces cerevisiae is known to activate a number of target genes in response to the presence of heme. Several features of the protein, deduced from the sequence of the gene, suggest that CYP1 is a general sensor of the redox state of the cell. To investigate further the function of CYP1, we analysed its effects on the transcription of two genes, HEM13 and 14DM, which are preferentially expressed in anaerobiosis. HEM13 encodes coproporphyrinogen oxidase which catalyses the sixth enzymatic step in the heme biosynthetic pathway and 14DM encodes lanosterol-14-demethylase which is involved in sterol biosynthesis and is a member of the cytochrome P450 family. Isogenic CYP1+ and cyp1 degree deleted strains, either heme-sufficient or heme-deficient (HEM1 disrupted), were grown in aerobic or anaerobic conditions, and transcripts of HEM13 and 14DM were analysed on Northern blots. The results show that in anaerobic and in heme-deficient cells, CYP1 activates the transcription of HEM13 and inhibits that of 14DM. Opposite effects of CYP1 are observed in aerobic, heme-sufficient cells. We concluded that: (i) CYP1 is an efficient activator especially in heme-depleted cells; (ii) CYP1 exerts both positive and negative regulatory effects; (iii) the nature of the regulatory function of CYP1 depends on the target gene; and (iv) for a given gene, the presence or absence of heme or oxygen reverses the sense of CYP1-dependent regulation.