DNA sequence-directed cooperation between nucleoid-associated proteins.
Ontology highlight
ABSTRACT:
SUBMITTER: Japaridze A
PROVIDER: S-EPMC8099737 | biostudies-literature |
REPOSITORIES: biostudies-literature
Similar Datasets
Project description:Many prokaryotic and eukaryotic genomes feature a characteristic periodic signal in distribution of short runs of A or T (A-tracts) phased with the DNA helical period of ∼10-11 bp. Such periodic spacing of A-tracts has been associated with intrinsic DNA curvature. In eukaryotes, this periodicity is a major component of the nucleosome positioning signal but its physiological role in prokaryotes is not clear. One hypothesis centers on possible role of intrinsic DNA bends in nucleoid compaction. We use comparative genomics to investigate possible relationship between the A-tract periodicity and nucleoid-associated proteins in prokaryotes. We found that genomes with DNA-bridging proteins tend to exhibit stronger A-tract periodicity, presumably indicative of more prevalent intrinsic DNA curvature. A weaker relationship was detected for nucleoid-associated proteins that do not form DNA bridges. We consider these results an indication that intrinsic DNA curvature acts collaboratively with DNA-bridging proteins in maintaining the compact structure of the nucleoid, and that previously observed differences among prokaryotic genomes in terms DNA curvature-related sequence periodicity may reflect differences in nucleoid organization. We subsequently investigated the relationship between A-tract periodicity and presence of CRISPR elements and we found that genomes with CRISPR tend to have stronger A-tract periodicity. This result is consistent with our earlier hypothesis that extensive A-tract periodicity could help protect the chromosome against integration of prophages, possibly due to its role in compaction of the nucleoid.
| S-EPMC3940949 | biostudies-literature
Project description:The H-NS family of proteins has been shown to participate in the regulation of a large number of genes in Gram-negative bacteria in response to environmental factors. In recent years, it has become apparent that proteins of the Hha family are essential elements for H-NS-regulated gene expression. Hha has been shown to bind H-NS, although the details for this interaction are still unknown. In the present paper, we report fluorescence anisotropy and NMR studies of the interaction between Hha and H-NS64, a truncated form of H-NS containing only its N-terminal dimerization domain. We demonstrate the initial formation of a complex between one Hha and two H-NS64 monomers in 150 mM NaCl. This complex seems to act as a nucleation unit for higher-molecular-mass complexes. NMR studies suggest that Hha is in equilibrium between two different conformations, one of which is stabilized by binding to H-NS64. A similar exchange is also observed for Hha in the absence of H-NS when temperature is increased to 37 degrees C, suggesting a key role for intrinsic conformational changes of Hha in modulating its interaction with H-NS.
| S-EPMC1183454 | biostudies-other
Project description:The Escherichia coli CrfC protein is an important regulator of nucleoid positioning and equipartition. Previously we revealed that CrfC homo-oligomers bind the clamp, a DNA-binding subunit of the DNA polymerase III holoenzyme, promoting colocalization of the sister replication forks, which ensures the nucleoid equipartition. In addition, CrfC localizes at the cell pole-proximal loci via an unknown mechanism. Here, we demonstrate that CrfC localizes to the distinct subnucleoid structures termed nucleoid poles (the cell pole-proximal nucleoid-edges) even in elongated cells as well as in wild-type cells. Systematic analysis of the nucleoid-associated proteins (NAPs) and related proteins revealed that HU, the most abundant NAP, and SlmA, the nucleoid occlusion factor regulating the localization of cell division apparatus, promote the specific localization of CrfC foci. When the replication initiator DnaA was inactivated, SlmA and HU were required for formation of CrfC foci. In contrast, when the replication initiation was inhibited with a specific mutant of the helicase-loader DnaC, CrfC foci were sustained independently of SlmA and HU. H-NS, which forms clusters on AT-rich DNA regions, promotes formation of CrfC foci as well as transcriptional regulation of crfC. In addition, MukB, the chromosomal structure mainetanice protein, and SeqA, a hemimethylated nascent DNA region-binding protein, moderately stimulated formation of CrfC foci. However, IHF, a structural homolog of HU, MatP, the replication terminus-binding protein, Dps, a stress-response factor, and FtsZ, an SlmA-interacting factor in cell division apparatus, little or only slightly affected CrfC foci formation and localization. Taken together, these findings suggest a novel and unique mechanism that CrfC localizes to the nucleoid poles in two steps, assembly and recruitment, dependent upon HU, MukB, SeqA, and SlmA, which is stimulated directly or indirectly by H-NS and DnaA. These factors might concordantly affect specific nucleoid substructures. Also, these nucleoid dynamics might be significant in the role for CrfC in chromosome partition.
| S-EPMC6374313 | biostudies-literature
Project description:The HPB12 protein from the nucleoid of Bacillus subtilis was previously described, and its DNA binding properties have been reported previously (V. Salti, F. Le Hégarat, and L. Hirschbein, Biochim. Biophys. Acta 1009:161-167, 1989). The DNA-HPB12 complexes were examined by electron microscopy. They appeared as short, slightly curved rods whereas naked DNA showed no compaction. Since only a small number of complexes with an intermediate degree of folding were observed, it appears that the nucleoid-associated protein HPB12 binds cooperatively to DNA, confirming Salti et al. (V. Salti, F. Le Hégarat, and L. Hirschbein, Biochim. Biophys. Acta 1009:161-167, 1989), and gives rise to a tightly compacted DNA-protein complex. N-terminal sequencing of purified HPB12 showed that all but one of the first 26 amino acids were identical to those of the L24 ribosomal protein.
| S-EPMC205013 | biostudies-other
Project description:By analyzing protein-protein interaction (PPI) networks, one can find that a protein may have multiple binding partners. However, it is difficult to determine whether the interactions with these partners occur simultaneously from binary PPIs alone. Here, we construct the yeast and human competition-cooperation relationship networks (CCRNs) based on protein structural interactomes to clearly exhibit the relationship (competition or cooperation) between two partners of the same protein. If two partners compete for the same interaction interface, they would be connected by a competitive edge; otherwise, they would be connected by a cooperative edge. The properties of three kinds of hubs (i.e., competitive, modest, and cooperative hubs) are analyzed in the CCRNs. Our results show that competitive hubs have higher clustering coefficients and form clusters in the human CCRN, but these tendencies are not observed in the yeast CCRN. We find that the human-specific proteins contribute significantly to these differences. Subsequently, we conduct a series of computational experiments to investigate the regulatory mechanisms that avoid competition between proteins. Our comprehensive analyses reveal that for most yeast and human protein competitors, transcriptional regulation plays an important role. Moreover, the human-specific proteins have a particular preference for other regulatory mechanisms, such as alternative splicing.
| S-EPMC4479874 | biostudies-other
Project description:Base and nucleotide excision repair (BER and NER) pathways are normally associated with removal of specific types of DNA damage: small base modifications (such as those induced by DNA oxidation) and bulky DNA lesions (such as those induced by ultraviolet or chemical carcinogens), respectively. However, growing evidence indicates that this scenario is much more complex and these pathways exchange proteins and cooperate with each other in the repair of specific lesions. In this review, we highlight studies discussing the involvement of NER in the repair of DNA damage induced by oxidative stress, and BER participating in the removal of bulky adducts on DNA. Adding to this complexity, UVA light experiments revealed that oxidative stress also causes protein oxidation, directly affecting proteins involved in both NER and BER. This reduces the cell's ability to repair DNA damage with deleterious implications to the cells, such as mutagenesis and cell death, and to the organisms, such as cancer and aging. Finally, an interactome of NER and BER proteins is presented, showing the strong connection between these pathways, indicating that further investigation may reveal new functions shared by them, and their cooperation in maintaining genome stability.
| S-EPMC7198027 | biostudies-literature
Project description:The intrinsic stiffness of DNA limits its ability to be bent and twisted over short lengths, but such deformations are required for gene regulation. One classic paradigm is DNA looping in the regulation of the Escherichia coli lac operon. Lac repressor protein binds simultaneously to two operator sequences flanking the lac promoter. Analysis of the length dependence of looping-dependent repression of the lac operon provides insight into DNA deformation energetics within cells. The apparent flexibility of DNA is greater in vivo than in vitro, possibly because of host proteins that bind DNA and induce sites of flexure. Here we test DNA looping in bacterial strains lacking the nucleoid proteins HU, IHF or H-NS. We confirm that deletion of HU inhibits looping and that quantitative modeling suggests residual looping in the induced operon. Deletion of IHF has little effect. Remarkably, DNA looping is strongly enhanced in the absence of H-NS, and an explanatory model is proposed. Chloroquine titration, psoralen crosslinking and supercoiling-sensitive reporter assays show that the effects of nucleoid proteins on looping are not correlated with their effects on either total or unrestrained supercoiling. These results suggest that host nucleoid proteins can directly facilitate or inhibit DNA looping in bacteria.
| S-EPMC1919473 | biostudies-literature
Project description:Comparisons of proteins show that they evolve through the movement of domains. However, in many cases, the underlying mechanisms remain unclear. Here, we observed the movements of DNA recognition domains between non-orthologous proteins within a prokaryote genome. Restriction-modification (RM) systems, consisting of a sequence-specific DNA methyltransferase and a restriction enzyme, contribute to maintenance/evolution of genomes/epigenomes. RM systems limit horizontal gene transfer but are themselves mobile. We compared Type III RM systems in Helicobacter pylori genomes and found that target recognition domain (TRD) sequences are mobile, moving between different orthologous groups that occupy unique chromosomal locations. Sequence comparisons suggested that a likely underlying mechanism is movement through homologous recombination of similar DNA sequences that encode amino acid sequence motifs that are conserved among Type III DNA methyltransferases. Consistent with this movement, incongruence was observed between the phylogenetic trees of TRD regions and other regions in proteins. Horizontal acquisition of diverse TRD sequences was suggested by detection of homologs in other Helicobacter species and distantly related bacterial species. One of these RM systems in H. pylori was inactivated by insertion of another RM system that likely transferred from an oral bacterium. TRD movement represents a novel route for diversification of DNA-interacting proteins.
| S-EPMC3467074 | biostudies-literature
Project description:Recent experimental work has demonstrated facilitated dissociation of certain nucleoid-associated proteins that exhibit an unbinding rate that depends on the concentration of freely diffusing proteins or DNA in solution. This concentration dependence arises due to binding competition with these other proteins or DNA. The identity of the binding competitor leads to different qualitative trends, motivating an investigation to understand observed differences in facilitated dissociation. We use a coarse-grained simulation that takes into account the dimeric nature of many nucleoid-associated proteins by allowing an intermediate binding state. The addition of this partially bound state allows the protein to be unbound, partially bound, or fully bound to a DNA strand, leaving opportunities for other molecules in solution to participate in the unbinding mechanism. Previous models postulated symmetric binding energies for each state of the coarse-grained protein corresponding to the symmetry of the dimeric protein; this model relaxes this assumption by assigning different energies for the different steps in the unbinding process. Allowing different unbinding energies not only has equilibrium effects on the system, but kinetic effects as well. We were able to reproduce the unbinding trends seen experimentally for both DNA and protein competitors. All trends collapse to a universal curve regardless of the unbinding energies used or the identity of the dissociation facilitator, suggesting that facilitated dissociation can be described with a single set of scaling parameters that are related to the energy landscape and geometric nature of the competitors.
| S-EPMC5300787 | biostudies-other
Project description:The Escherichia coli K-12 nir operon promoter can be fully activated by binding of the regulator of fumarate and nitrate reduction (FNR) to a site centered at position -41.5 upstream of the transcript start, and this activation is modulated by upstream binding of the integration host factor (IHF) and Fis (factor for inversion stimulation) proteins. Thus, transcription initiation is repressed by the binding of IHF and Fis to sites centered at position -88 (IHF I) and position -142 (Fis I) and activated by IHF binding to a site at position -115 (IHF II). Here, we have exploited mutational analysis and biochemistry to investigate the actions of IHF and Fis at these sites. We show that the effects of IHF and Fis are position dependent and that IHF II functions independently of IHF I and Fis I. Using in vitro assays, we report that IHF and Fis repress transcription initiation by interfering with RNA polymerase binding. Differences in the upstream IHF and Fis binding sites at the nir promoter in related enteric bacteria fix the level of nir operon expression under anaerobic growth conditions.
| S-EPMC2580697 | biostudies-literature