Regions in the promoter of the yeast FBP1 gene implicated in catabolite repression may bind the product of the regulatory gene MIG1.

We have identified in the promoter of the yeast FBP1 gene two sites able to bind nuclear proteins. These sites have a nucleotide sequence strongly similar to that of sites which bind the regulatory protein MIG1 in the promoters of GAL4 and SUC2. Deletions performed in the FBP1 promoter showed that one of the sites contributes to catabolite repression of this gene. In this same promoter, another region was identified with a strong effect on the catabolite repression of FBP1. In this region a sequence similar to the consensus for the binding site of the MIG1 protein was also present.     

DNA sequence determinants for binding of the Escherichia coli catabolite gene activator protein.

The consensus DNA site for binding of the Escherichia coli catabolite gene activator protein (CAP) is 22 base pairs in length and is 2-fold symmetric: 5'-AAATGTGATCTAGATCACATTT-3'. Positions 4 to 8 of each half of the consensus DNA half-site are the most strongly conserved. In this report, we analyze the effects of substitution of DNA base pairs at positions 4 to 8, the effects of substitution of thymine by uracil and by 5-methylcytosine at positions 4, 6, and 8, and the effect of dam methylation of the 5'-GATC-3' sequence at positions 7 to 10. All DNA sites having substitutions of DNA base pairs at positions 4 to 8 exhibit lower affinities for CAP than does the consensus DNA site, consistent with the proposal that the consensus DNA site is the ideal DNA site for CAP. Specificity for T:A at position 4 appears to be determined solely by the thymine 5-methyl group. Specificity for T:A at position 6 and specificity for A:T at position 8 appear to be determined in part, but not solely, by the thymine 5-methyl group. dam methylation has little effect on CAP.DNA complex formation. The thermodynamically defined consensus DNA site spans 28 base pairs. All, or nearly all, DNA determinants required for maximal affinity for CAP and for maximal thermodynamically defined CAP.DNA ion pair formation are contained within a 28-base pair DNA fragment that has the 22-base pair consensus DNA site at its center. The quantitative data in this report provide base-line thermodynamic data required for detailed investigations of amino acid-base pair and amino acid-phosphate contacts in this protein-DNA complex.     

The glucose repressor CRE1 from Sclerotinia sclerotiorum is functionally related to CREA from Aspergillus nidulans but not to the Mig proteins from Saccharomyces cerevisiae.

We isolated the putative glucose repressor gene cre1 from the phytopathogenic fungus Sclerotinia sclerotiorum. cre1 encodes a 429 amino acid protein 59% similar to the carbon catabolite repressor CREA from Aspergillus nidulans. In addition to the overall amino acid sequence relatedness between CRE1 and CREA proteins, cre1 can functionally complement the A. nidulans creAd30 mutation as assessed by repression of the alcohol dehydrogenase I gene expression. The CREI region carrying the two zinc fingers is also very similar to the DNA binding domains of the Saccharomyces cerevisiae glucose repressors Mig1p and Mig2p. Despite the presence in the CRE1 protein of several motifs involved in the regulation of Miglp activity, cre1 cannot complement mig deficiencies in S. cerevisiae. These data suggest that glucose repression pathways may have evolved differently in yeasts and filamentous fungi.     

Cyclic adenosine 3',5'-monophosphate levels in Pseudomonas putida and Pseudomonas aeruginosa during induction and carbon catabolite repression of histidase synthesis.

Inducibility of histidase (histidine ammonia-lyase, EC 4.3.1.3) in Pseudomonas putida and Pseudomonas aeruginosa was observed to be strongly affected by succinate-provoked catabolite repression, but this did not occur as a consequence of reduced intracellular cyclic adenosine 3',5'-monophosphate levels, and repression could not be alleviated by exogenously added cyclic adenosine 3,'5'-monophosphate. Milder repression of histidase by lactate was also not reversed by the addition of cyclic adenosine 3',5'-monophosphate. These results, along with data showing intracellular cyclic adenosine 3',5'-monophosphate levels remained essentially constant during growth on such diverse carbon sources as histidine, acetamide, glucose, and succinate, indicated that catabolite repression of histidase synthesis by efficient carbon sources was not mediated through variations in internal cyclic adenosine 3,'5'-monophosphate.     

Glucose kinase has a regulatory role in carbon catabolite repression in Streptomyces coelicolor.

A glucose kinase (glkA) mutant of Streptomyces coelicolor A3(2) M145 was selected by the ability to grow in the presence of the nonmetabolizable glucose analog 2-deoxyglucose. In this glkA mutant, carbon catabolite repression of glycerol kinase and agarase was relieved on several carbon sources tested, even though most of these carbon sources are not metabolized via glucose kinase. This suggests that catabolite repression is not regulated by the flux through glucose kinase and that the protein itself has a regulatory role in carbon catabolite repression. A 10-fold overproduction of glucose kinase also results in relief of catabolite repression, suggesting that excess glucose kinase can titrate the repressing signal away. This could be achieved directly by competition of excess glucose kinase with its repressing form for binding sites on DNA promoter regions or indirectly by competition for binding of another regulatory protein.     

Nitrogen catabolite repression in Saccharomyces cerevisiae.

In Saccharomyces cerevisiae the expression of all known nitrogen catabolite pathways are regulated by four regulators known as Gln3, Gat1, Dal80, and Deh1. This is known as nitrogen catabolite repression (NCR). They bind to motifs in the promoter region to the consensus sequence 5'GATAA 3'. Gln3 and Gat1 act positively on gene expression whereas Dal80 and Deh1 act negatively. Expression of nitrogen catabolite pathway genes known to be regulated by these four regulators are glutamine, glutamate, proline, urea, arginine. GABA, and allantonie. In addition, the expression of the genes encoding the general amino acid permease and the ammonium permease are also regulated by these four regulatory proteins. Another group of genes whose expression is also regulated by Gln3, Gat1, Dal80, and Deh1 are some proteases, CPS1, PRB1, LAP1, and PEP4, responsible for the degradation of proteins into amino acids thereby providing a nitrogen source to the cell. In this review, all known promoter sequences related to expression of nitrogen catabolite pathways are discussed as well as other regulatory proteins. Overview of metabolic pathways and promotors are presented.