Identification of hypoxanthine and guanine as the co‐repressors for the purine regulon genes of <i>Escherichia coli</i>

Meng, Li Mei; Nygaard, Per

doi:10.1111/j.1365-2958.1990.tb00580.x

Cited by 82 publications

(71 citation statements)

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“…Gel retardation assays were performed as described previously with buffer system II for corepressor-dependent binding (23 Table 2 also show that part of the sixfold repression by adenine was dependent upon purR, and about one-half was purR independent. Therefore, the threefold purR-dependent repression by adenine was likely due to its conversion to hypoxanthine and guanine (21), which are corepressors for PurR (16,23 by adenine, but the effects of hypoxanthine and guanine were not seen, and the role of purR was not investigated.…”

Section: Methodsmentioning

confidence: 99%

“…More recent information indicates that purB expression is coregulated with those of otherpur regulon genes by the purine repressor (PurR) (9, 15). PurR requires binding of hypoxanthine or guanine corepressors for interaction with a conserved 16-bp operator sequence (16,23). The position of the operator relative to the promoter varies among the pur regulon genes and in part determines the extent and mechanism of transcriptional regulation.…”

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Regulation of Escherichia coli purA by purine repressor, one component of a dual control mechanism

Zalkin

1994

J Bacteriol

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Escherichia colipurA encodes adenylosuccinate synthetase, one of two enzymes required for synthesis of AMP from IMP. purA is subject to two-to threefold regulation by purR and about twofold regulation by a purR-independent mechanism. The 5'-flanking region ofpurA confers purR-dependent transcriptional regulation ofpurA but not the purR-independent regulation. Two operator sites in the 5'-flanking region which bind purine repressor in vitro and are required for in vivo regulation were identified. The purR-independent regulation may be posttranscriptional. It is now established that all transcription units involved in de novo synthesis of purine nucleotides, nine pur operons, as well as purR itself and guaBA, are subject to purR control.Adenylosuccinate synthetase (EC 6.3.2.6), the product of the purA gene in Escherichia coli, catalyzes the first of two reactions from the IMP branch point to AMP in the de novo purine nucleotide biosynthetic pathway (21). The second reaction to AMP is catalyzed by adenylosuccinate lyase (EC 4.2.2.2), the product of purB. Genetically, purA is located at min 95 on the E. coli chromosome and is unlinked to otherpur regulon genes (1). The purA gene has been cloned and sequenced (32), and its expression is modulated by the levels of purines in the growth medium (31). On the basis of assays of adenylosuccinate synthetase used to monitor purA expression and 0-galactosidase for purB-lacZ expression, it was concluded that purA and purB are regulated separately (31). More recent information indicates that purB expression is coregulated with those of otherpur regulon genes by the purine repressor (PurR) (9, 15). PurR requires binding of hypoxanthine or guanine corepressors for interaction with a conserved 16-bp operator sequence (16,23). The position of the operator relative to the promoter varies among the pur regulon genes and in part determines the extent and mechanism of transcriptional regulation. In purB, the operator is far downstream from the promoter in the protein coding region (9). purB is regulated only about two-to threefold, whereas genes dedicated to the de novo synthesis of IMP are more highly regulated (8,9,15).Here, we report the results of experiments to determine the regulatory mechanism for purA. The purA gene is subject to dual regulation by levels of purines in the medium. One mechanism, described here, involves PurR-operator control. In addition, there is purR-independent regulation of purA. MATERIALS AND METHODSBacterial strains, plasmids, and media. The strains and plasmids used in this work are listed in Table 1. LB and 2 x YT media (18) were used as rich media. The minimal growth medium has been described previously (8).Plasmid construction. To clone the purA control region, a segment of purA from nucleotides -478 to + 103, numbered relative to the start of transcription (Fig. 1) was subcloned into the EcoRI-BamHI site of pUC118, resulting in plasmid pBH140. In a similar way, a 178-bp fragment from nucleotides -72 to +103 was constructed and was ligated into the Ec...

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Section: Methodsmentioning

confidence: 99%

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confidence: 99%

Regulation of Escherichia coli purA by purine repressor, one component of a dual control mechanism

Zalkin

1994

J Bacteriol

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“…PurR, a repressor protein for genes encoding enzymes used in purine and pyrimidine nucleotide biosynthesis (Rolfes & Zalkin, 1988a, b;Kilstrup et al, 1989 ;Meng & Nygaard, 1990), negatively regulates the g b A gene (Steiert et al, 1990(Steiert et al, , 1992. PurR was shown to bind upstream of the g b A promoter and protect from DNase I attack a 24 bp region that overlaps the gbA promoter (Steiert e t al., 1992).…”

Section: Introductionmentioning

confidence: 99%

“…PurR was shown to bind upstream of the g b A promoter and protect from DNase I attack a 24 bp region that overlaps the gbA promoter (Steiert e t al., 1992). Hypoxanthine and guanine, corepressors of PurR for genes in theptlr regulon (Houlberg & Jensen, 1983;Rolfes & Zalkin, 198813;Kilstrup e t al., 1989;Meng & Nygaard, 1990), increased the affinity of PurR for thegbA operator in an in vitro gel mobility-shift Abbreviation : RNAP, RNA polymerase.…”

Section: Introductionmentioning

confidence: 99%

RNA polymerase, PurR and MetR interactions at the glyA promoter of Escherichia coli

Lorenz

Stauffer

1996

Microbiology

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In Escherichia coli, the MetR and PurR proteins positively and negatively regulate g/yA gene expression, respectively. A DNase I footprint analysis showed that both proteins bind independently to the g/yA control region. The PurR protein blocks RNA polymerase (RNAP) from binding to the g/yA promoter. The presence of hypoxanthine, the co-repressor of PurR, increases the ability of PurR to prevent RNAP binding, providing a model for repression of the g/yA gene by PurR. In contrast, MetR alters the RNAP footprint pattern of the g/yA control region. In addition, the MetR footprint is increased in the presence of RNAP, suggesting that the two proteins might interact.

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“…PurR, a repressor of several operons involved in nucleotide metabolism (Meng & Nygaard, 1990 ;Rolfes & Zalkin, 1988), represses gcvT ::lacZ expression twofold when cells are grown in the presence of purines Wilson et al, 1993a). PurR binds to a site from about base k3 to j17 relative to the transcription initiation site, and possibly interferes with RNA polymerase (RNAP) binding to the gcv promoter (Wilson et al, 1993a).…”

Section: Abbreviationsmentioning

confidence: 99%

GcvA binding site 1 in the gcvTHP promoter of Escherichia coli is required for GcvA-mediated repression but not for GcvA-mediated activation

2000

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GcvA binds to three sites in the gcvTHP control region, from base N34 to N69 (site 1), from base N214 to N241 (site 2) and from base N242 to N271 (site 3).Previous results suggested that sites 3 and 2 are required for both GcvAdependent activation and repression of a gcvT ::lacZ fusion. However, the results were less clear as to the role of site 1. To determine the role of site 1 in regulation, single and multiple base changes were made in site 1 and tested for their ability to alter GcvA-mediated activation and GcvA/GcvR-mediated repression. Several of the mutants were also tested for effects on GcvA binding to site 1 and the ability of GcvA to bend DNA at site 1. The results are consistent with site 1 playing primarily a role in negative regulation of the gcvTHP operon.

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Identification of hypoxanthine and guanine as the co‐repressors for the purine regulon genes of Escherichia coli

Cited by 82 publications

References 21 publications

Regulation of Escherichia coli purA by purine repressor, one component of a dual control mechanism

Regulation of Escherichia coli purA by purine repressor, one component of a dual control mechanism

RNA polymerase, PurR and MetR interactions at the glyA promoter of Escherichia coli

GcvA binding site 1 in the gcvTHP promoter of Escherichia coli is required for GcvA-mediated repression but not for GcvA-mediated activation

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