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Bacillus subtilis LrpC is a sequence-independent DNA-binding and DNA-bending protein which bridges DNA.

ABSTRACT: Genetic evidence suggests that the Bacillus subtilis lrpC gene product participates in cell growth and sporulation. The purified LrpC protein, which has a predicted molecular mass of 16.4 kDa, is a tetramer in solution. LrpC binds with higher affinity ( K (app) approximately 80 nM) to intrinsically curved DNA than to non-curved DNA ( K (app) approximately 700 nM). DNase I footprinting and the supercoiling of relaxed circular plasmid DNA in the presence of topoisomerase I revealed that LrpC induces DNA bending and constrains DNA supercoils in vitro. The LrpC protein cooperatively increases DNA binding of the bona fide DNA-binding and DNA-bending protein Hbsu. LrpC forms inter- and intramolecular bridges on linear and supercoiled DNA molecules, resulting in a large network and DNA compactation. Collectively, these findings suggest that LrpC is an architectural protein and that its activities could provide a means to modulate DNA transactions.

SUBMITTER: Tapias A

PROVIDER: S-EPMC102501 | biostudies-literature | 2000 Jan

REPOSITORIES: biostudies-literature

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Bacillus subtilis LrpC is a sequence-independent DNA-binding and DNA-bending protein which bridges DNA.

Tapias A A López G G Ayora S S

Nucleic acids research 20000101 2

Genetic evidence suggests that the Bacillus subtilis lrpC gene product participates in cell growth and sporulation. The purified LrpC protein, which has a predicted molecular mass of 16.4 kDa, is a tetramer in solution. LrpC binds with higher affinity ( K (app) approximately 80 nM) to intrinsically curved DNA than to non-curved DNA ( K (app) approximately 700 nM). DNase I footprinting and the supercoiling of relaxed circular plasmid DNA in the presence of topoisomerase I revealed that LrpC induc ...[more]

PMID: 10606655

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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 ?whiA 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 ?whiA ?parAB 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.

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Dataset Information

Bacillus subtilis LrpC is a sequence-independent DNA-binding and DNA-bending protein which bridges DNA.

Publications

Bacillus subtilis LrpC is a sequence-independent DNA-binding and DNA-bending protein which bridges DNA.

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