Abstract
Every organism across the tree of life compacts and organizes its genome with architectural chromatin proteins. While eukaryotes and archaea express histone proteins, the organization of bacterial chromosomes is dependent on nucleoid-associated proteins. In Escherichia coli and other proteobacteria, the histone-like nucleoid structuring protein (H-NS) acts as a global genome organizer and gene regulator. Functional analogues of H-NS have been found in other bacterial species: MvaT in Pseudomonas species, Lsr2 in actinomycetes and Rok in Bacillus species. These proteins complement hns− phenotypes and have similar DNA-binding properties, despite their lack of sequence homology. In this review, we focus on the structural and functional characteristics of these four architectural proteins. They are able to bridge DNA duplexes, which is key to genome compaction, gene regulation and their response to changing conditions in the environment. Structurally the domain organization and charge distribution of these proteins are conserved, which we suggest is at the basis of their conserved environment responsive behaviour. These observations could be used to find and validate new members of this protein family and to predict their response to environmental changes.
Highlights
All organisms compact and organize their genomic DNA
A newly proposed functional homologue of histone-like nucleoid structuring protein (H-NS) is the repressor of comK protein (Rok) of Bacillus subtilis. This classification is primarily based on the observation that Rok binds extended regions of the B. subtilis genome and especially A/T rich regions acquired by horizontal gene transfer, which it aids to repress [39]
We focus on the properties of DNAbridging proteins in bacteria with a proposed role in genome architecture and gene regulation: H-NS, MvaT, Lsr2 and Rok
Summary
All organisms compact and organize their genomic DNA. Structuring of the genome is achieved by the action of small, basic architectural proteins that interact with DNA. These proteins have similar DNA-binding properties, resulting in the formation of structurally and functionally similar protein–DNA complexes This ability is elegantly demonstrated by the genetic complementation of hns− phenotypes (like mucoidy, motility and β-glucoside utilization) in E. coli by MvaT from Pseudomonas species and Lsr from Mycobacterium and related actinomycetes [31,32]. This classification is primarily based on the observation that Rok binds extended regions of the B. subtilis genome and especially A/T rich regions acquired by horizontal gene transfer, which it aids to repress [39] This specific property of silencing foreign genes makes Rok, just like H-NS, MvaT and Lsr, a xenogeneic silencer. We discuss the mechanisms by which the architectural and regulatory properties of these proteins are modulated
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