The homologous operons for P1 and P7 plasmid partition are autoregulated from dissimilar operator sites

Hayes, Finbarr; Radnedge, Lyndsay; Davis, Michael A.; Austin, Stuart

doi:10.1111/j.1365-2958.1994.tb00305.x

Cited by 63 publications

(93 citation statements)

References 46 publications

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“…This arrangement permits ParB to contact a variety of A-and B-box combinations within parS. As functional studies predicted, the crystal structure of ParB-(142-333) confirms that the HTH motif binds the A-boxes within parS and the dimerization domain binds the B-boxes (15)(16)(17)(18). The dimerization interaction creates a novel DNA binding motif that requires contributions from each monomer to bind a box B sequence.…”

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confidence: 76%

P1 Partition Complex Assembly Involves Several Modes of Protein-DNA Recognition

Vecchiarelli

Schumacher

Funnell

2007

Journal of Biological Chemistry

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Assembly of P1 plasmid partition complexes at the partition site, parS, is nucleated by a dimer of P1 ParB and Escherichia coli integration host factor (IHF), which promotes loading of more ParB dimers and the pairing of plasmids during the cell cycle. ParB binds several copies of two distinct recognition motifs, known as A-and B-boxes, which flank a bend in parS created by IHF binding. The recent crystal structure of ParB bound to a partial parS site revealed two relatively independent DNA-binding domains and raised the question of how a dimer of ParB recognizes its complicated arrangement of recognition motifs when it loads onto the full parS site in the presence of IHF. In this study, we addressed this question by examining ParB binding activities to parS mutants containing different combinations of the A-and B-box motifs in parS. Binding was measured to linear and supercoiled DNA in electrophoretic and filter binding assays, respectively. ParB showed preferences for certain motifs that are dependent on position and on plasmid topology. In the simplest arrangement, one motif on either side of the bend was sufficient to form a complex, although affinity differed depending on the motifs. Therefore, a ParB dimer can load onto parS in different ways, so that the initial ParB-IHF-parS complex consists of a mixture of different orientations of ParB. This arrangement supports a model in which parS motifs are available for inter-as well as intramolecular parS recognition.

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confidence: 76%

P1 Partition Complex Assembly Involves Several Modes of Protein-DNA Recognition

Vecchiarelli

Schumacher

Funnell

2007

Journal of Biological Chemistry

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“…The recognition site for ParA is likely a large inverted repeat in the par promoter region, since (i) several mutations in this repeat reduce or eliminate ParA repression in vivo (13) and (ii) in DNase I footprinting experiments, protection centers over the inverted repeat, especially at low ParA concentrations (8,14). ParA DNA binding activity is strongly stimulated by ATP (8,14).…”

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confidence: 99%

Modulation of the P1 Plasmid Partition Protein ParA by ATP, ADP, and P1 ParB

Davey

Funnell

1997

Journal of Biological Chemistry

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ParA is an essential P1 plasmid partition protein. It represses transcription of the par genes (parA and parB) and is also required for a second, as yet undefined step in partition. ParA is a ParB-stimulated ATPase that binds to a specific DNA site in the par promoter region. ParA is an essential component of the P1 plasmid partition system (1). The prophage of bacteriophage P1 exists as an autonomously replicating plasmid, and its copy number is about the same as that of the bacterial chromosome (2). The P1 partition system, Par, directs proper segregation and thus stable maintenance of the plasmid. The mechanism of partition is unknown, but can be thought of as a positioning process that via interaction with the Escherichia coli host ensures proper distribution of the plasmid. Par encodes two essential transacting proteins, ParA and ParB, and contains a cis-acting DNA site called parS (1). In addition, the E. coli integration host factor, IHF, 1 also participates, although it is not absolutely required (3). ParB and IHF bind to parS to form the partition complex (3-5). Assembly of this complex is assumed to be an early step in the partition pathway. Formation of this complex does not require the action of ParA (3-5), and we infer that ParA acts during a later step in the partition process.ParA has at least two roles in partition. First, ParA represses transcription of its own gene and parB from a promoter upstream of parA (6). ParA repressor activity is stimulated by ParB; however, ParB has no effect on par gene expression on its own. A second role for ParA in partition is inferred from genetic data that show a requirement for ParA in partition even when its regulatory role is bypassed (6, 7). Therefore, we consider ParA's repressor activity its "regulatory" function, and this second, as yet undefined role as ParA's "partition" function because we think it reflects a direct role for ParA in the positioning reaction. The latter function requires that ParA interact, directly or indirectly, with the ParB-IHF-parS partition complex.ParA is an ATPase and a site-specific DNA-binding protein (8). The ATPase is stimulated by ParB and nonspecific DNA (8). ParA is one of the better characterized proteins in a superfamily of ATPases defined by a modified Walker type A motif in the protein sequence (9 -11). This superfamily includes other plasmid partition proteins such as F SopA, as well as plasmid and chromosomally encoded proteins from various bacteria species whose functions have not yet been determined (10 -12). Many of the plasmids and bacterial chromosomes also encode a ParB homolog adjacent to the ParA homolog. The similarities of these ParA-like proteins with P1 ParA and F SopA have led to the suggestion that these homologs are also involved in plasmid or chromosome segregation (10, 11).ParA binds to the par promoter region called parOP (8), and this binding is thought to mediate ParA repressor activity in vivo. The recognition site for ParA is likely a large inverted repeat in the par promoter region, since (i) ...

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“…Its site-specific DNA binding protein, ParB, binds to the parS partition site. In addition to its direct role in the partition mechanism, P1 ParA acts as a repressor of the par operon by site-specific DNA binding to the par operator, parOP (4,5). Repression by ParA is strongly stimulated by ParB in vivo and indirectly influences the partition mechanism by regulating parA and parB transcription.…”

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confidence: 99%

“…ADP is a better cofactor than ATP for its site-specific binding activity to parOP (25). ParA also binds to nonspecific DNA (nsDNA) 4 , and this activity absolutely requires ATP (11). In P1 ParA, nsDNA binding requires a slow conformational change in the protein that occurs after binding of ATP, forming ParA-ATP* (11).…”

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confidence: 99%