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The Role of Escherichia coli Protein H‐NS in Chromosome Integrity
Author(s) -
Pina Cara,
Lovett Susan
Publication year - 2015
Publication title -
the faseb journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.709
H-Index - 277
eISSN - 1530-6860
pISSN - 0892-6638
DOI - 10.1096/fasebj.29.1_supplement.878.10
Subject(s) - escherichia coli , chromosome , chemistry , genetics , biology , microbiology and biotechnology , gene
H‐NS is an abundant nucleoid associated protein within Escherichia coli . Notably, H‐NS has been implicated in DNA structure and organization as well as chromosome integrity. The dimerization, oligomerization, and DNA binding of H‐NS protein are thought to be necessary for its abundant and varying physiological roles. To elucidate the mechanistic roles of H‐NS in maintaining DNA integrity, we have generated chromosomal point mutants within the dimerization (L30P), oligomerization (Y61G), or nucleic acid binding (P116A) domain. Using these mutants, we evaluated chromosomal structure, chromosome organization, and cell survival. The hnsL30P mutant chromosome appears similar to an hns null strain , showing very few chromosome abnormalities in rich media. In contrast, the hnsP116A mutant exhibits defective chromosome segregation seemingly preventing cell division. Interestingly, the hnsY61G mutant displays abnormal chromosome segregation and aberrant cell division, producing an increase in anucleate cells and cells with irregular DNA quantities. These results support the involvement of H‐NS in proper positioning of the DNA for reliable segregation. Culture growth in both hnsY61G and hnsP116A is significantly impaired, most likely due to the loss of chromosomal integrity. An additional deletion of slmA , an inhibitor of cell division over the nucleoid, produces an appreciable decline in culture growth in all mutants except hnsY61G . This additionally suggests the growth deficiency in an hnsY61G mutant strain may be a result of defects in nucleoid occlusion specifically. These findings implicate H‐NS in midcell positioning of the nucleoid as well as chromosome integrity through proper nucleoid occlusion. Future experiments seek to examine the process of cellular division in H‐NS mutants through live cell imaging and evaluation of the population of non‐reproductive daughter cells.