Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UNIPROT:P51532 (transcriptional activator)
 6,546 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Apart from serving as a prosthetic group in globins and enzymes, heme is a key regulator controlling a wide range of molecular and cellular processes involved in oxygen sensing and utilization. To gain insights into molecular mechanisms of heme signaling and oxygen sensing in eukaryotes, we investigated the yeast heme-responsive transcriptional activator HAP1. HAP1 activity is regulated precisely and tightly by heme. Here we show that in the absence of heme, HAP1 forms a biochemically distinctive higher-order complex. Our data suggest that this complex contains HAP1 and four other cellular proteins including Hsp82 and Ydj1. The formation of this complex is directly correlated with HAP1 repression in the absence of heme, and mutational or heme disruption of the complex correlates with HAP1 activation, suggesting that this complex is responsible for heme regulation of HAP1 activity. Further, we determined HAP1 domains required for heme regulation: three domains-the dimerization domain, the heme domain, and the HRM7 (heme-responsive motif 7) domain-cooperate to form the higher-order complex and mediate heme regulation. Strikingly, we uncovered a novel function for the HAP1 dimerization domain: it not only allows dimerization but also provides critical functions in heme regulation and transcriptional activation. Our studies provide significant insights into the molecular events leading to heme activation of HAP1 and may shed light on molecular mechanisms of various heme-controlled biological processes in diverse organisms.
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PMID:Molecular mechanism governing heme signaling in yeast: a higher-order complex mediates heme regulation of the transcriptional activator HAP1. 963 66

HAP1 is a yeast transcriptional activator that binds with equal affinity to the dissimilar upstream activation sequences UAS1 and UAS(CYC7), but activates transcription differentially when bound to each site. HAP1-18 harbors an amino acid change in the DNA binding domain. While binding UAS1 poorly, HAP1-18 binds UAS(CYC7) with wild-type properties and activates transcription at elevated levels relative to HAP1. We have determined the structure of HAP1-18-UAS(CYC7) and have compared it to HAP1-UAS(CYC7). Unexpectedly, the single amino acid substitution in HAP1-18 nucleates a significantly altered hydrogen bond interface between the protein and DNA resulting in DNA conformational changes and an ordering of one N-terminal arm of the protein dimer along the DNA minor groove. These observations, together with a large subset of transcriptionally defective mutations in the HAP1 DNA-binding domain that map to the HAP1-DNA interface, suggest that protein-DNA interactions may have direct allosteric effects on transcriptional activation.
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PMID:Structure of HAP1-18-DNA implicates direct allosteric effect of protein-DNA interactions on transcriptional activation. 988 87

In this work we have cloned and characterized the Kluyveromyces lactis HAP1 gene and we have found that, contrary to data previously described for the homologous gene of Saccharomyces cerevisiae, i.) the function of this gene does not affect growth in media with carbon sources used by fermentative or respiratory pathways ii) in aerobiosis, KlHap1p is not a transcriptional activator of the expression of genes related to respiration, cholesterol biosynthesis or oxidative stress defence analyzed in this study. The comparison of homology between specific regions of ScHap1p and KlHap1p reveals that the dimerization domain is poorly conserved and we have verified that this domain, cloned in the two plasmids of the two hybrid system, does not reconstitute S. cerevisiae Gal4p activity. Since the COOH-terminal transcriptional activation domain of KlHap1p is active when fused to the Gal4p-DNA binding domain, we hypothesize that differences in the capacity to form dimers could contribute to allow different functions of the protein in K. lactis and S. cerevisiae. Transcriptional expression of KlHAP1 is dependent on oxygen availability, increasing its expression in hypoxia. Deletion of KlHAP1 increases the resistance to oxidative stress or cadmium and the induction of KlYAP1 and KlTSA1 by the addition of 0.5 mM H(2)O(2) is repressed by KlHap1p. These data are discussed in reference to the evolution of respiro-fermentative metabolism in yeasts.
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PMID:Functional characterization of KlHAP1: a model to foresee different mechanisms of transcriptional regulation by Hap1p in yeasts. 1794 45


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