title: Locus of enterocyte effacement-encoded regulator (Ler) of pathogenic Escherichia coli competes off histone-like nucleoid-structuring protein (H-NS) through noncooperative DNA binding.
abstract: The locus of enterocyte effacement-encoded regulator (Ler) of enteropathogenic and enterohemorrhagic Escherichia coli (EPEC and EHEC) functions to activate transcription of virulence genes silenced by the histone-like nucleoid-structuring protein (H-NS). Despite its important role in the bacterial gene regulation, the binding mode of Ler to DNA and its mechanism in alleviating genes repressed by H-NS are largely unknown. In this study, we use magnetic tweezers to demonstrate that Ler binds extended DNA through a largely noncooperative process, which results in DNA stiffening and DNA folding depending on protein concentration. We also show that Ler can replace prebound H-NS on DNA over a range of potassium and magnesium concentrations. Our findings reveal the DNA binding properties of Ler and shed light to further understand the anti-silencing activity of Ler.
authors.affiliation: From the NUS Graduate School for Integrative Sciences and Engineering, National University of Singapore, Singapore 117456, Singapore, the Mechanobiology Institute, Singapore 117411, Singapore, the Centre for BioImaging Sciences, National University of Singapore, Singapore 117543, Singapore.
authors.forename: Ricksen S
authors.initials: RS
authors.lastname: Winardhi
authors.affiliation: the Mechanobiology Institute, Singapore 117411, Singapore, the Centre for BioImaging Sciences, National University of Singapore, Singapore 117543, Singapore.
authors.forename: Ranjit
authors.initials: R
authors.lastname: Gulvady
authors.affiliation: the Biology Department, Reed College, Portland, Oregon 97202, and jay.mellies@reed.edu.
authors.forename: Jay L
authors.initials: JL
authors.lastname: Mellies
authors.affiliation: the Mechanobiology Institute, Singapore 117411, Singapore, the Centre for BioImaging Sciences, National University of Singapore, Singapore 117543, Singapore, the Department of Physics, National University of Singapore, Singapore 117542, Singapore phyyj@nus.edu.sg.
authors.forename: Jie
authors.initials: J
authors.lastname: Yan
mesh_terms: D001426:Bacterial Proteins / Q000378:metabolism*; D001667:Binding, Competitive; D004269:DNA, Bacterial / Q000737:chemistry / Q000378:metabolism*; D004268:DNA-Binding Proteins / Q000378:metabolism*; D004305:Dose-Response Relationship, Drug; D054324:Enterohemorrhagic Escherichia coli / Q000235:genetics / Q000378:metabolism*; D054308:Enteropathogenic Escherichia coli / Q000235:genetics / Q000378:metabolism*; D029968:Escherichia coli Proteins / Q000378:metabolism*; D006863:Hydrogen-Ion Concentration; D015636:Magnesium Chloride / Q000494:pharmacology; D009690:Nucleic Acid Conformation; D011189:Potassium Chloride / Q000494:pharmacology; D011485:Protein Binding / Q000187:drug effects; D013379:Substrate Specificity; D013696:Temperature; D015534:Trans-Activators / Q000378:metabolism*
chemical_list: D001426:Bacterial Proteins; D004269:DNA, Bacterial; D004268:DNA-Binding Proteins; D029968:Escherichia coli Proteins; C031908:H-NS protein, bacteria; C465556:Ler protein, E coli; D015534:Trans-Activators; D015636:Magnesium Chloride; D011189:Potassium Chloride
keywords: Atomic Force Microscopy; DNA-binding Protein; Gene Regulation; H-NS; Ler; Magnetic Tweezers; Protein-DNA Interaction; Single Molecule Biophysics