Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound   Target Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound

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Query: EC:3.2.1.23 (beta-galactosidase)
14,648 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The LPD1 gene of Saccharomyces cerevisiae, encoding lipoamide dehydrogenase (LPDH), is subject to catabolite repression. The promoter of this gene contains a number of motifs for DNA-binding transcriptional activators, including three which show strong sequence homology to the core HAP2/HAP3/HAP4 binding motif. Here we report that transcription of LPD1 requires HAP2, HAP3 and HAP4 for release from glucose repression. In the wild-type strain, specific activity of LPDH was increased 12-fold by growth on lactate, 10-fold on glycerol and four- to five-fold on galactose or raffinose, compared to growth on glucose. In hap2, hap3 and hap4 null mutants, the specific activities of LPDH in cultures grown on galactose and raffinose showed only slight induction above the basal level on glucose medium. Similar results were obtained upon assaying for beta-galactosidase production in wild-type, or hap2, hap3 or hap4 mutant strains carrying a single copy of the LPD1 promoter fused in frame to the lacZ gene of Escherichia coli and integrated at the URA3 locus. Transcript analysis in wild-type and hap2 mutants confirmed that the HAP2 protein regulates LPD1 expression at the level of transcription in the same way as it does for the CYC1 gene. Site-directed mutagenesis of the putative HAP2/HAP3/HAP4 binding site at -204 relative to the ATG start codon showed that this element was required for full derepression of the LPD1 gene on non-fermentable substrates.
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PMID:Positive regulation of the LPD1 gene of Saccharomyces cerevisiae by the HAP2/HAP3/HAP4 activation system. 131 May 23

By deletion analysis of the fusion genes FBP1-lacZ and PCK1-lacZ we have identified a number of strong regulatory regions in the genes FBP1 and PCK1 which encode fructose-1,6-bisphosphatase and phosphoenolpyruvate carboxykinase. Lack of expression of beta-galactosidase in fusions lacking sequences from the coding regions suggests the existence of downstream activating elements. Both promoters have several UAS and URS regions as well as sites implicated in catabolite repression. We have found in both genes consensus sequences for the binding of the same regulatory proteins, such as yAP1, MIG1 or the complex HAP2/HAP3/HAP4. Neither deletion nor overexpression of the MIG1 gene affected the regulated expression of the FBP1 or PCK1 genes.
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PMID:Regulatory regions in the yeast FBP1 and PCK1 genes. 132 78

The RAG1 gene encodes a membrane protein involved in the low-affinity glucose/fructose transport system of the yeast Kluyveromyces lactis. Analysis of steady-state mRNA levels analysis and quantitation of expression by beta-galactosidase from RAG1-lacZ fusions assays revealed that the RAG1 gene was poorly expressed in cells grown under gluconeogenesis conditions, but was induced more than ten-fold when they were grown on various sugars. These sugars included glucose, fructose, mannose, sucrose, raffinose, as well as galactose. Nucleotide sequence and deletion analysis of the 5' flanking region of the RAG1 gene showed that an essential cis-acting element required for induced transcription of the RAG1 gene resided between -615 and -750 from the coding sequence. This region contained a 22 bp purine stretch, and a pair of 11 bp direct repeat sequences. The 11 bp repeats harbor a CCAAT motif, a consensus sequence for binding of the yeast and mammalian HAP2/3/4-type protein complex. The transcription of the RAG1 gene was dramatically affected by three unlinked mutations, rag4, rag5 and rag8. We discuss the possible roles of RAG4, RAG5 and RAG8 gene products in the expression of the RAG1 gene, as well as the importance of the inducible RAG1 gene in the fermentative growth of K. lactis.
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PMID:Glucose transport in the yeast Kluyveromyces lactis. II. Transcriptional regulation of the glucose transporter gene RAG1. 160 79

We have examined the expression of the gene encoding the iron-protein subunit (Ip) of succinate dehydrogenase in Saccharomyces cerevisiae. The gene had been cloned by us and shown to be subject to glucose regulation (A. Lombardo, K. Carine, and I. E. Scheffler, J. Biol. Chem. 265:10419-10423, 1990). We discovered that a significant part of the regulation of the Ip mRNA levels by glucose involves the regulation of the turnover rate of this mRNA. In the presence of glucose, the half-life appears to be less than 5 min, while in glycerol medium, the half-life is greater than 60 min. The gene is also regulated transcriptionally by glucose. The upstream promoter sequence appeared to have four regulatory elements with consensus sequences shown to be responsible for the interaction with the HAP2/3/4 regulatory complex. A deletion analysis has shown that the two distal elements are redundant. These measurements were carried out by Northern (RNA) analyses of Ip mRNA transcripts as well as by assays of beta-galactosidase activity in cells carrying constructs of the Ip promoter linked to the lacZ coding sequence. These observations on the regulation of mRNA stability were also extended to the mRNA of the flavoprotein subunit of succinate dehydrogenase and in some experiments of iso-1-cytochrome c.
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PMID:Control of mRNA turnover as a mechanism of glucose repression in Saccharomyces cerevisiae. 162 Jan 7

Yeast mutants assigned to the pet complementation group G104 were found to lack alpha-ketoglutarate dehydrogenase activity as a result of mutations in the dihydrolipoyl transsuccinylase (KE2) component of the complex. The nuclear gene KGD2, coding for yeast KE2, was cloned by transformation of E250/U6, a G104 mutant, with a yeast genomic library. Analysis of the KGD2 sequence revealed an open reading frame encoding a protein with a molecular weight of 52,375 and 42% identities to the KE2 component of Escherichia coli alpha-ketoglutarate dehydrogenase complex. Disruption of the chromosomal copy of KGD2 in a respiratory-competent haploid yeast strain elicited a growth phenotype similar to that of G104 mutants and abolished the ability to mitochondria to catalyze the reduction of NAD+ by alpha-ketoglutarate. The expression of KGD2 was transcriptionally regulated by glucose. Northern (RNA) analysis of poly(A)+ RNA indicated the existence of two KGD2 transcripts differing in length by 150 nucleotides. The concentrations of both RNAs were at least 10 times lower in glucose (repressed)- than in galactose (derepressed)-grown cells. Different 5'-flanking regions of KGD2 were fused to the lacZ gene of E. coli in episomal plasmids, and the resultant constructs were tested for expression of beta-galactosidase in wild-type yeast cells and in hap2 and hap3 mutants. Results of the lacZ fusion assays indicated that transcription of KGD2 is activated by the HAP2 and HAP3 proteins. The regulated expression of KGD2 was found to depend on sequences that map to a region 244 to 484 nucleotides upstream of the structural gene. This region contains two short sequence elements that differ by one nucleotide from the consensus core (5'-TN[A/G]TTGGT-3') that has been proposed to be essential for binding of the HAP activation complex. These data together with earlier reports on the regulation of the KGD1 and LPD1 genes for the alpha-ketoglutarate and dihydrolipoyl dehydrogenases indicate that all three enzyme components of the complex are catabolite repressed and subject to positive regulation by the HAP2 and HAP3 proteins.
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PMID:Structure and regulation of KGD2, the structural gene for yeast dihydrolipoyl transsuccinylase. 211 21

In Saccharomyces cerevisiae, the COR2 gene codes for the 40 kDa subunit II of the QH2: cytochrome c oxidoreductase, an enzyme of the mitochondrial respiratory chain. Regions in the 5' flank of this gene important for regulated expression were identified by assaying beta-galactosidase activities in cells carrying different COR2-lacZ fusion genes. Sequences downstream of position -201 relative to the translational initiation codon are sufficient to confer regulation by carbon source, whereas sequences downstream of position -153 do not give rise to significant expression. A binding site for the abundant general transcription factor GFI is present in the region between -201 and -153 just upstream from sequences which resemble the consensus DNA recognition sequence of the regulatory protein complex HAP2/HAP3: 5'-TNATTGGT-3'. By quantitating RNA levels and assaying beta-galactosidase activities we show that synthesis of COR2, which is not a hemoprotein, is regulated by HAP1, HAP2/HAP3 and heme.
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PMID:Expression of the gene encoding subunit II of yeast QH2: cytochrome c oxidoreductase is regulated by multiple factors. 216 71

Nuclear respiratory-defective mutants of Saccharomyces cerevisiae have been screened for lesions in the mitochondrial alpha-ketoglutarate dehydrogenase complex. Strains assigned to complementation group G70 were ascertained to be deficient in enzyme activity due to mutations in the KGD1 gene coding for the alpha-ketoglutarate dehydrogenase component of the complex. The KGD1 gene has been cloned by transformation of a representative kgd1 mutant, C225/U1, with a recombinant plasmid library of wild-type yeast nuclear DNA. Transformants containing the gene on a multicopy plasmid had three- to four-times-higher alpha-ketoglutarate dehydrogenase activity than did wild-type S. cerevisiae. Substitution of the chromosomal copy of KGD1 with a disrupted allele (kgd1::URA3) induced a deficiency in alpha-ketoglutarate dehydrogenase. The sequence of the cloned region of DNA which complements kgd1 mutants was found to have an open reading frame of 3,042 nucleotides capable of coding for a protein of Mw 114,470. The encoded protein had 38% identical residues with the reported sequence of alpha-ketoglutarate dehydrogenase from Escherichia coli. Two lines of evidence indicated that transcription of KGD1 is catabolite repressed. Higher steady-state levels of KGD1 mRNA were detected in wild-type yeast grown on the nonrepressible sugar galactose than in yeast grown on high glucose. Regulation of KGD1 was also studied by fusing different 5'-flanking regions of KGD1 to the lacZ gene of E. coli and measuring the expression of beta-galactosidase in yeast. Transformants harboring a fusion of 693 nucleotides of the 5'-flanking sequence expressed 10 times more beta-galactosidase activity when grown under derepressed conditions. The response to the carbon source was reduced dramatically when the same lacZ fusion was present in a hap2 or hap3 mutant. The promoter element(s) responsible for the regulated expression of KGD1 has been mapped to the -354 to -143 region. This region contained several putative activation sites with sequences matching the core element proposed to be essential for binding of the HAP2 and HAP3 regulatory proteins.
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PMID:Structure and regulation of KGD1, the structural gene for yeast alpha-ketoglutarate dehydrogenase. 250 10

The COX6 gene encodes subunit VI of cytochrome c oxidase. Previously, this gene and its mRNAs were characterized, and its expression has been shown to be subject to glucose repression/derepression. In this study we have examined the effects of heme and the HAP1 (CYP1) and HAP2 genes on the expression of COX6. By quantitating COX6 RNA levels and assaying beta-galactosidase activity in yeast cells carrying COX6-lacZ fusion genes, we have found that COX6 is regulated positively by heme and HAP2, but is unaffected by HAP1. Through 5' deletion analysis we have also found that the effects of heme and HAP2 on COX6 are mediated by sequences between 135 and 590 base pairs upstream of its initiation codon. These findings identify COX6 as the fourth respiratory protein gene that is known to be regulated positively by heme and HAP2. The other three, CYC1, COX4, and COX5a, encode iso-1-cytochrome c, cytochrome c oxidase subunit IV, and an isolog, Va, of cytochrome c oxidase subunit V, respectively. Thus, it appears that the biogenesis of two interacting proteins, cytochrome c and cytochrome c oxidase, in the mitochondrial respiratory chain, are under the control of common factors.
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PMID:Transcription of yeast COX6, the gene for cytochrome c oxidase subunit VI, is dependent on heme and on the HAP2 gene. 254 Jan 69

Transcriptional activation by the yeast CYC1 upstream activation site UAS2UP1 requires the products of both the HAP2 and HAP3 regulatory genes. We show here that both HAP2 and HAP3 in yeast extracts bind to UAS2UP1 and give rise to a single protein-DNA complex, termed C, in nondenaturing polyacrylamide gels. That both products are a part of complex C was shown by altering the mobility of the complex by fusing either HAP2 or HAP3 to beta-galactosidase. Further, methylation interference footprinting showed that sequences in UAS2UP1 contacted in complex C were identical to those contacted in either fusion protein complex. Binding was centered on the sequence TGATTGGT, also found in the UASs of other genes subject to activation by the HAP2-HAP3 system and homologous to the CCAAT box sequence found in higher cells. The binding of either HAP2 or HAP3 was abolished when synthesized in a strain mutant in the complementary HAP gene. Thus the binding of HAP2 and HAP3 to UAS2UP1 is interdependent. The involvement of multiple gene products in binding to a single site is discussed with reference to other systems in yeast and higher cells.
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PMID:Yeast HAP2 and HAP3 activators both bind to the CYC1 upstream activation site, UAS2, in an interdependent manner. 282 15

Transcription of the yeast C upsilon C1 gene (iso-1-cytochrome c) is regulated in part by the upstream activation site UAS2. Activity of UAS2 requires both the HAP2 and HAP3 activators, which bind to UAS2 in an interdependent manner. To distinguish whether these factors bound to UAS2 cooperatively or formed a complex in the absence of DNA, HAP2 and HAP3 were tagged by gene fusion to LexA and beta-galactosidase, respectively, and purified through four chromatographic steps. The copurification of LexA-HAP2, HAP3 beta-galactosidase, and UAS2 binding activity shows that HAP2 and HAP3 associate in the absence of DNA to form a multisubunit activation complex.
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PMID:Yeast HAP2 and HAP3: transcriptional activators in a heteromeric complex. 283 51


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