High-order oligomerization is required for the function of the H-NS family member MvaT in Pseudomonas aeruginosa

Division of Infectious Diseases, Children's Hospital, Harvard Medical School, Boston, MA 02115, USA.
Molecular Microbiology (Impact Factor: 5.03). 11/2010; 78(4):916-31. DOI: 10.1111/j.1365-2958.2010.07378.x
Source: PubMed

ABSTRACT H-NS is an abundant DNA-binding protein that has been implicated in the silencing of foreign DNA in several different bacteria. The ability of H-NS dimers to form higher-order oligomers is thought to aid the polymerization of the protein across AT-rich stretches of DNA and facilitate gene silencing. Although the oligomerization of H-NS from enteric bacteria has been the subject of intense investigation, little is known regarding the oligomerization of H-NS family members from bacteria outside of the enterobacteriaceae, many of which share little sequence similarity with their enteric counterparts. Here we show that MvaT, a member of the H-NS family of proteins from Pseudomonas aeruginosa, can form both dimers and higher-order oligomers, and we identify a region within MvaT that mediates higher-order oligomer formation. Using genetic assays we identify mutants of MvaT that are defective for higher-order oligomer formation. We present evidence that these mutants are functionally impaired and exhibit DNA-binding defects because of their inability to form higher-order oligomers. Our findings support a model in which the ability of MvaT to bind efficiently to the DNA depends upon protein-protein interactions between MvaT dimers and suggest that the ability to form higher-order oligomers is a conserved and essential feature of H-NS family members.

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