Inhibition of Transcription of the Histidine Operon
            <i>In Vitro</i>
            by the First Enzyme of the Histidine Pathway

Blasi, Francesco; Bruni, Carmelo B.; Avitabile, A.; Deeley, Roger G.; Goldberger, Robert F.; Meyers, Marilyn

doi:10.1073/pnas.70.9.2692

Cited by 34 publications

(11 citation statements)

References 34 publications

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“…Evidence implicating the product (G enzyme, or N-1-[5'-phosphoribosyl]adenosine triphosphate:pyrophosphate phosphoribosyltransferase; EC 2.4.2.17) of the first structural gene (hisG) of the operon in the regulation (7)(8)(9)(10)(11) has led to the idea that this protein would interact with charged tRNAHiS and might fulfill the role of a classical repressor (e.g., discussion in ref. 9 and ref.…”

mentioning

confidence: 99%

Histidine regulation in Salmonella typhimurium: an activator attenuator model of gene regulation.

Artz¹,

Broach²

1975

Proc. Natl. Acad. Sci. U.S.A.

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An activator-attenuator model of positive control, as opposed to the classic repressor-operator model of negative control, is proposed for the major operon-specific mechanism governing expression of the histidine gene cluster of Salmonella typhimurium. Evidence for this mechanism is derived from experiments performed with a coupled in vitro transcription-translation system, as well as with a minimal in vitro transcription system [Kasai, T. (1974) The likelihood that tRNA and tRNA modifications are involved in regulating gene expression for all cells has accentuated the importance of understanding the mechanism of regulation of his operon expression in Salmonella typhimurium. It has been well established that charged tRNAHis is a negative effector in this mechanism (1), and that a particular modified base-pseudouridine (')-is necessary for the regulatory function of tRNAHis (2), as well as other tRNAs (3).A regulatory region (hisO) with some properties of a Jacob-Monod type of operator locus (4) has been characterized in the his operon (5), and this region has been referred to as the his "operator," or more currently (6), as the his "operator-promoter" locus. However, despite detailed studies of his operon regulation, direct evidence for a repressoroperator mechanism of gene regulation (4) has been lacking.Evidence implicating the product (G enzyme, or N-1-[5'-phosphoribosyl]adenosine triphosphate:pyrophosphate phosphoribosyltransferase; EC 2.4.2.17) of the first structural gene (hisG) of the operon in the regulation (7-11) has led to the idea that this protein would interact with charged tRNAHiS and might fulfill the role of a classical repressor (e.g., discussion in ref. 9 and ref. 11). This simple model for regulating his operon expression has been unsatisfying for a variety of reasons and is, in fact, eliminated by evidence considered in this paper.5'-diphosphate 3'-diphosphate/histidine G enzyme/ Recently, two investigators have introduced new concepts to explain the mechanism of his operon regulation. Based on genetic and physiological studies, Ely (12) proposed a model, similar to that earlier suggested by Gierer (13), in which DNA in the hisO region varies between a linear duplex structure competent in binding of RNA polymerase, and a transcriptionally inactive "loop" structure. Kasai (14), using evidence obtained with a minimal in vitro transcription system (containing RNA polymerase, DNA, and small molecules necessary for transcription), proposed a novel "attenuator" type of regulation in which a site in the hisO region acts as a "barrier" to transcription by RNA polymerase. Evidence from this laboratory was provided in support of the general concept of an attenuator mechanism (14).We have developed a coupled in vitro protein-synthesizing system (containing a crude cellular protein fraction, DNA, and small molecules necessary for transcription and translation), using strains of S. typhimurium.t This in vitro system mimics regulatory alterations observed in vivo with respect to mutations in the ...

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mentioning

confidence: 99%

Histidine regulation in Salmonella typhimurium: an activator attenuator model of gene regulation.

Artz¹,

Broach²

1975

Proc. Natl. Acad. Sci. U.S.A.

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“…In the 'histidine system' from Salmonella, for instance, it was found that the first enzyme of the pathway not only displays sensitivity to feedback inhibition by histidine, but also functions s20 as a corepressor for the operon as a whole, histidyltRNA being a corepressor. This has been shown both in vivo [42] and in vitro [43]. A somewhat similar situation has been encountered in the isoleucine biosynthesizing system [44] as well as in the hut operon [45] .…”

Section: North-holland Publishing Company -Amsterdammentioning

confidence: 67%

Control of gene expression in prokaryotic systems

Gros¹

1974

FEBS Letters

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“…2) maintain repressed levels of his enzymes when grown in minimal media containing excess histidine, and derepress normally when histidine is limited by growth on the histidine intermediate, histidinol (Table 2). With strains containing such internal hisG deletions (his-8473, -8474, -8476, and -8477), derepression ratios are in the range 11-16 and [8][9][10][11][12][13][14][15][16][17][18][19] for the hisD and hisB enzymes, respectively. These values compare with those of [8][9] for hisD enzyme and [13][14][15] for hisB enzyme, obtained with the hisG+ control strains (hisC483 and hisC537).…”

Section: Methodsmentioning

confidence: 99%

“…None of these classes has been demonstrated to alter any protein that serves directly as a repressor or activator protein. Several lines of evidence have suggested that the hisG enzyme ATP phosphoribosyltransferase [N-1-(5'-phosphoribosyl) ATP: pyrophosphate phosphoribosyltransferase, EC 2.4.2.17] might be the missing regulatory element (5)(6)(7)(8)(9)(10)(11). This protein is the first enzyme in the biosynthetic pathway and is encoded by the first structural gene in the operon.…”

mentioning

confidence: 99%

Regulation of histidine operon does not require hisG enzyme.

Scott

Roth²,

Artz

1975

Proc. Natl. Acad. Sci. U.S.A.

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Mutations are described which delete all or part of the first structural gene (hisG) of the histidine operon of Salmonella typhimurium. Physiological regulation of histidine enzymes occurs normally in strains carrying any deletion that has both endpoints within the hisG gene. Constitutive high operon expression is observed in strains carrying any hisG deletion and an unlinked regulatory mutation, hisT1504. These results strongly indicate that the hisG protein is not an essential component of the mechanism for regulating expression of the histidine operon.The biosynthesis of histidine in Salmonella typhimurium requires ten enzymes. The structural genes for these enzymes are located in a cluster of coordinately regulated genes (1, 2) called the histidine operon. Six classes of regulatory mutations have been identified which cause constitutive high level expression of the operon. These are hisR, hisS, hisT, hisU, hisW, and hisO. Characteristics of each of the classes are described in recent review articles (3, 4). None of these classes has been demonstrated to alter any protein that serves directly as a repressor or activator protein. Several lines of evidence have suggested that the hisG enzyme ATP phosphoribosyltransferase [N-1-(5'-phosphoribosyl) ATP: pyrophosphate phosphoribosyltransferase, EC 2.4.2.17] might be the missing regulatory element (5-11). This protein is the first enzyme in the biosynthetic pathway and is encoded by the first structural gene in the operon.In the work reported here, mutants lacking all or part of the hisG gene have been selected as less polar derivatives of hisG frameshift mutations. The general method is similar to that used previously by Jackson and Yanofsky (12). These hisG deletions were mapped at high resolution with known point and deletion mutations. Regulation of the his operon was then studied in strains containing hisG deletions. This paper describes the isolation and mapping of the deletions and the results of studies of their regulatory properties.MATERIALS AND METHODS Bacterial Strains. Genotypes and sources of S. typhimurium strains are listed in Table 1. The strongly polar point mutations hisG6608 and hisG6609 were isolated by selection for temperature resistance of a strain containing the his01242 constitutive regulatory mutation (13). Mutations hisG6608 and hisG6609 were separated from the his01242 mutation by transduction. Strains containing the numerous his mutations used in localizing endpoints of hisG deletions (Fig. 2) were obtained from P. E. Hartman and B. N. Ames.Growth Media. Difco nutrient broth was used as the maximally supplemented liquid medium, with 2 g of agar per 100 ml added for solid medium. The E medium of Abbreviations: HT phage, high-frequency transducing phage; AT, 3-amino-1,2,4-triazole. t Present address:

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Inhibition of Transcription of the Histidine Operon In Vitro by the First Enzyme of the Histidine Pathway

Cited by 34 publications

References 34 publications

Histidine regulation in Salmonella typhimurium: an activator attenuator model of gene regulation.

Histidine regulation in Salmonella typhimurium: an activator attenuator model of gene regulation.

Control of gene expression in prokaryotic systems

Regulation of histidine operon does not require hisG enzyme.

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