Premium
The DNA ‐Binding Protein HU has a Regulatory Role in the Acid Stress Response Mechanism in H elicobacter pylori
Author(s) -
Almarza Oscar,
Núñez Daniel,
Toledo Hector
Publication year - 2015
Publication title -
helicobacter
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.206
H-Index - 79
eISSN - 1523-5378
pISSN - 1083-4389
DOI - 10.1111/hel.12171
Subject(s) - mutant , histone , chromatin , dna , dna damage , microbiology and biotechnology , biology , dna binding domain , biochemistry , gene , chemistry , transcription factor
Abstract Background Bacterial genomes are compacted by association with histone‐like proteins to form a complex known as bacterial chromatin. The histone‐like protein HU is capable of binding and bending the DNA molecule, a function related to compaction, protection, and regulation of gene expression. In H elicobacter pylori , HU is the only histone‐like protein described so far. Proteomic analysis from our laboratory showed that this protein is overexpressed under acidic stress. Materials and Methods We used a purified recombinant wild‐type protein and two mutant proteins with the amino acid substitutions K3A/S27D and K62R/V63N/P64A to characterize the function of the N‐terminal domain and the flexible arm of HU . Results In vitro assays for DNA protection, bending, and compaction were performed. We also designed a H . pylori hup::cat mutant strain to study the role of HU in the acid stress response. HU wt protein binds DNA and promotes its bending and compaction. Compared with the wild‐type protein, both mutant proteins have less affinity for DNA and an impaired bending and compaction ability. By using q RT ‐ PCR , we confirmed overexpression of two genes related to acid stress response ( ureA and speA ). Such overexpression was abolished in the hup::cat strain, which shows an acid‐sensitive phenotype. Conclusions Altogether, we have shown that HU wt – DNA complex formation is favored under acidic pH and that the complex protects DNA from endonucleolytic cleavage and oxidative stress damage. We also showed that the amino‐terminal domain of HU is relevant to DNA –protein complex formation and that the flexible arm of HU is involved in the bending and compaction activities of HU .