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Soj (ParA) DNA binding is mediated by conserved arginines and is essential for plasmid segregation.

ABSTRACT: Soj is a member of the ParA family of ATPases involved in plasmid and chromosomal segregation. It binds nonspecifically and cooperatively to DNA although the function of this binding is unknown. Here, we show that mutation of conserved arginine residues that map to the surface of Bacillus subtilis Soj caused only minimal effects on nucleotide-dependent dimerization but had dramatic effects on DNA binding. Using a model plasmid partitioning system in Escherichia coli, we find that Soj DNA-binding mutants are deficient in plasmid segregation. The location of the arginines on the Soj structure explains why DNA binding depends on dimerization and was used to orient the Soj dimer on the DNA, revealing the axis of Soj polymerization. The arginine residues are conserved among other chromosomal homologues, including the ParAs from Caulobacter crescentus, Pseudomonas aeruginosa, Pseudomonas putida, Streptomyces coelicolor, and chromosome I of Vibrio cholerae indicating that DNA binding is a common feature of members of this family.

SUBMITTER: Hester CM

PROVIDER: S-EPMC2154430 | biostudies-literature | 2007 Dec

REPOSITORIES: biostudies-literature

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Soj (ParA) DNA binding is mediated by conserved arginines and is essential for plasmid segregation.

Hester Christina M CM Lutkenhaus Joe J

Proceedings of the National Academy of Sciences of the United States of America 20071211 51

Soj is a member of the ParA family of ATPases involved in plasmid and chromosomal segregation. It binds nonspecifically and cooperatively to DNA although the function of this binding is unknown. Here, we show that mutation of conserved arginine residues that map to the surface of Bacillus subtilis Soj caused only minimal effects on nucleotide-dependent dimerization but had dramatic effects on DNA binding. Using a model plasmid partitioning system in Escherichia coli, we find that Soj DNA-binding ...[more]

PMID: 18077387

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Project description:The DNA binding protein WhiA is conserved in Gram-positive bacteria and is present in the genetically simple cell wall-lacking mycoplasmas. The protein shows homology to eukaryotic homing endonucleases but lacks nuclease activity. WhiA was first characterized in streptomycetes, where it regulates the expression of key differentiation genes, including the cell division gene ftsZ, which is essential for sporulation. For Bacillus subtilis, it was shown that WhiA is essential when certain cell division genes are deleted. However, in B. subtilis, WhiA is not required for sporulation, and it does not seem to function as a transcription factor, despite its DNA binding activity. The exact function of B. subtilis WhiA remains elusive. We noticed that whiA mutants show an increased space between their nucleoids, and here, we describe the results of fluorescence microscopy, genetic, and transcriptional experiments to further investigate this phenomenon. It appeared that the deletion of whiA is synthetic lethal when either the DNA replication and segregation regulator ParB or the DNA replication inhibitor YabA is absent. However, WhiA does not seem to affect replication initiation. We found that a ΔwhiA mutant is highly sensitive for DNA-damaging agents. Further tests revealed that the deletion of parAB induces the SOS response, including the cell division inhibitor YneA. When yneA was inactivated, the viability of the synthetic lethal ΔwhiA ΔparAB mutant was restored. However, the nucleoid segregation phenotype remained. These findings underline the importance of WhiA for cell division and indicate that the protein also plays a role in DNA segregation.IMPORTANCE The conserved WhiA protein family can be found in most Gram-positive bacteria, including the genetically simple cell wall-lacking mycoplasmas, and these proteins play a role in cell division. WhiA has some homology with eukaryotic homing endonucleases but lacks nuclease activity. Because of its DNA binding activity, it is assumed that the protein functions as a transcription factor, but this is not the case in the model system B. subtilis The function of this protein in B. subtilis remains unclear. We noticed that a whiA mutant has a mild chromosome segregation defect. Further studies of this phenomenon provided new support for a functional role of WhiA in cell division and indicated that the protein is required for normal chromosome segregation.

Dataset Information

Soj (ParA) DNA binding is mediated by conserved arginines and is essential for plasmid segregation.

Publications

Soj (ParA) DNA binding is mediated by conserved arginines and is essential for plasmid segregation.

Similar Datasets

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