Abstract
Global regulators play an essential role in the adaptation of bacterial cells to specific niches. Bacterial pathogens thriving in the tissues and organs of their eukaryotic hosts are a well-studied example. Some of the proteins that recognize local DNA structures rather than specific nucleotide sequences act as global modulators in many bacteria, both Gram-negative and -positive. To this class of regulators belong the H-NS-like proteins, mainly identified in γ-Proteobacteria, and the MgaSpn-like proteins identified in Firmicutes. H-NS and MgaSpn from Escherichia coli and Streptococcus pneumoniae, respectively, neither have sequence similarity nor share structural domains. Nevertheless, they display common features in their interaction with DNA, namely: (i) they bind to DNA in a non-sequence-specific manner, (ii) they have a preference for intrinsically curved DNA regions, and (iii) they are able to form multimeric complexes on linear DNA. Using DNA fragments from the hemolysin operon regulatory region of the E. coli plasmid pHly152, we show in this work that MgaSpn is able to recognize particular regions on extended H-NS binding sites. Such regions are either located at or flanked by regions of potential bendability. Moreover, we show that the regulatory region of the pneumococcal P1623B promoter, which is recognized by MgaSpn, contains DNA motifs that are recognized by H-NS. These motifs are adjacent to regions of potential bendability. Our results suggest that both regulatory proteins recognize similar structural characteristics of DNA.
Highlights
Global modulators play key roles in the ability of bacterial cells to rapidly adapt to environmental fluctuations by adjusting their gene expression pattern
By Electrophoretic Mobility Shift Assays (EMSA), we found that MgaSpn-His generates multimeric complexes on the hlyC DNA fragment (Supplementary Figure 1)
Proteins MgaSpn and H-NS are very different in size
Summary
Global modulators play key roles in the ability of bacterial cells to rapidly adapt to environmental fluctuations by adjusting their gene expression pattern. As a consequence, they enable the pathogenic bacteria to colonize and survive in different niches of their eukaryotic hosts. Some global modulators recognize specific DNA sequences, others exhibit a preference for particular DNA structures. Examples of the latter group are the H-NS-like proteins, mainly found in γ-Proteobacteria, and the MgaSpn-like proteins identified in Firmicutes. Interactions of MgaSpn and H-NS with DNA In Escherichia and Salmonella, the DNA-binding properties of the nucleoid-associated protein H-NS (137 amino acids) have been studied in detail (for a review see Winardhi et al, 2015).
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