Machine-Learning Single-Stranded DNA Nanoparticles for Bacterial Analysis.
Ontology highlight
ABSTRACT:
SUBMITTER: Nandu N
PROVIDER: S-EPMC8174836 | biostudies-literature |
REPOSITORIES: biostudies-literature
Similar Datasets
Project description:Single-stranded DNA-binding proteins (SSBs) are required for repair, recombination and replication in all organisms. Eukaryotic SSBs are regulated by phosphorylation on serine and threonine residues. To our knowledge, phosphorylation of SSBs in bacteria has not been reported. A systematic search for phosphotyrosine-containing proteins in Streptomyces griseus by immunoaffinity chromatography identified bacterial SSBs as a novel target of bacterial tyrosine kinases. Since genes encoding protein-tyrosine kinases (PTKs) have not been recognized in streptomycetes, and SSBs from Streptomyces coelicolor (ScSSB) and Bacillus subtilis (BsSSB) share 38.7% identity, we used a B.subtilis protein-tyrosine kinase YwqD to phosphorylate two cognate SSBs (BsSSB and YwpH) in vitro. We demonstrate that in vivo phosphorylation of B.subtilis SSB occurs on tyrosine residue 82, and this reaction is affected antagonistically by kinase YwqD and phosphatase YwqE. Phosphorylation of B.subtilis SSB increased binding almost 200-fold to single-stranded DNA in vitro. Tyrosine phosphorylation of B.subtilis, S.coelicolor and Escherichia coli SSBs occured while they were expressed in E.coli, indicating that tyrosine phosphorylation of SSBs is a conserved process of post-translational modification in taxonomically distant bacteria.
| S-EPMC1405823 | biostudies-literature
Project description:A retron is a bacterial retroelement that encodes an RNA gene and a reverse transcriptase (RT). The former, once transcribed, works as a template primer for reverse transcription by the latter. The resulting DNA is covalently linked to the upstream part of the RNA; this chimera is called multicopy single-stranded DNA (msDNA), which is extrachromosomal DNA found in many bacterial species. Based on the conserved features in the eight known msDNA sequences, we developed a detection method and applied it to scan National Center for Biotechnology Information (NCBI) RefSeq bacterial genome sequences. Among 16,844 bacterial sequences possessing a retron-type RT domain, we identified 48 unique types of msDNA. Currently, the biological role of msDNA is not well understood. Our work will be a useful tool in studying the distribution, evolution, and physiological role of msDNA.
| S-EPMC4838527 | biostudies-literature
Project description:Condensin is the major driving force in the segregation of daughter chromosomes in prokaryotes. Core subunits of condensin belong to the SMC protein family, whose members are characterized by a unique ATPase activity and dimers with a V-shaped structure. The V-shaped dimers might close between head domains, forming a ring structure that can encircle DNA. Indeed, cohesin, which is a subfamily of SMC proteins, encircles double-stranded DNA to hold sister chromatids in eukaryotes. However, the question of whether or not condensin encircles the chromosomal DNA remains highly controversial. Here we report that MukB binds topologically to DNA in vitro, and this binding is preferentially single-stranded DNA (ssDNA) rather than double-stranded DNA. The binding of MukB to ssDNA does not require ATP. In fact, thermal energy enhances the binding. The non-SMC subunits MukF and MukE did stimulate the topological binding of MukB, although they hindered DNA-binding of MukB. Recent reports on the distribution of condensin in genomes reveal that actively transcribed genes in yeast and humans are enriched in condensin. In consideration of all these results, we propose that the binding specificity of condensin to chromosome is provided not by the DNA sequence but by the DNA structure, which is ssDNA.
| S-EPMC4937444 | biostudies-literature
Project description:Bacteria encode homooligomeric single-stranded (ss) DNA-binding proteins (SSBs) that coat and protect ssDNA intermediates formed during genome maintenance reactions. The prototypical Escherichia coli SSB tetramer can bind ssDNA using multiple modes that differ by the number of bases bound per tetramer and the magnitude of the binding cooperativity. Our understanding of the mechanisms underlying cooperative ssDNA binding by SSBs has been hampered by the limited amount of structural information available for interfaces that link adjacent SSB proteins on ssDNA. Here we present a crystal structure of Bacillus subtilis SsbA bound to ssDNA. The structure resolves SsbA tetramers joined together by a ssDNA "bridge" and identifies an interface, termed the "bridge interface," that links adjacent SSB tetramers through an evolutionarily conserved surface near the ssDNA-binding site. E. coli SSB variants with altered bridge interface residues bind ssDNA with reduced cooperativity and with an altered distribution of DNA binding modes. These variants are also more readily displaced from ssDNA by RecA than wild-type SSB. In spite of these biochemical differences, each variant is able to complement deletion of the ssb gene in E. coli. Together our data suggest a model in which the bridge interface contributes to cooperative ssDNA binding and SSB function but that destabilization of the bridge interface is tolerated in cells.
| S-EPMC6331220 | biostudies-literature
Project description:Single-stranded DNA-binding proteins (SSBs) support DNA replication by protecting single-stranded DNA from nucleolytic attack, preventing intra-strand pairing events and playing many other regulatory roles within the replisome. Recent developments in single-molecule approaches have led to a revised picture of the replisome that is much more complex in how it retains or recycles protein components. Here, we visualize how an in vitro reconstituted Escherichia coli replisome recruits SSB by relying on two different molecular mechanisms. Not only does it recruit new SSB molecules from solution to coat newly formed single-stranded DNA on the lagging strand, but it also internally recycles SSB from one Okazaki fragment to the next. We show that this internal transfer mechanism is balanced against recruitment from solution in a manner that is concentration dependent. By visualizing SSB dynamics in live cells, we show that both internal transfer and external exchange mechanisms are physiologically relevant.
| S-EPMC6486552 | biostudies-literature
Project description:DNA2 is an essential enzyme involved in DNA replication and repair in eukaryotes. In a search for homologues of this protein, we identified and characterised Geobacillus stearothermophilus Bad, a bacterial DNA helicase-nuclease with similarity to human DNA2. We show that Bad contains an Fe-S cluster and identify four cysteine residues that are likely to co-ordinate the cluster by analogy to DNA2. The purified enzyme specifically recognises ss-dsDNA junctions and possesses ssDNA-dependent ATPase, ssDNA binding, ssDNA endonuclease, 5' to 3' ssDNA translocase and 5' to 3' helicase activity. Single molecule analysis reveals that Bad is a processive DNA motor capable of moving along DNA for distances of >4 kb at a rate of ?200 bp per second at room temperature. Interestingly, as reported for the homologous human and yeast DNA2 proteins, the DNA unwinding activity of Bad is cryptic and can be unmasked by inactivating the intrinsic nuclease activity. Strikingly, our experiments show that the enzyme loops DNA while translocating, which is an emerging feature of processive DNA unwinding enzymes. The bacterial Bad enzymes will provide an excellent model system for understanding the biochemical properties of DNA2-like helicase-nucleases and DNA looping motor proteins in general.
| S-EPMC7430649 | biostudies-literature
Project description:We describe experiments aimed at establishing whether circular single-stranded DNAs can form promoters for bacterial transcription from small folded motifs. In vitro selection experiments were carried out on circular 103-nt DNA libraries encoding 40-nt randomized sequences as well as self-processing hammerhead ribozymes. Rounds of rolling circle transcription, reverse transcription-PCR, and recyclization were carried out to optimize transcription efficiency. Sequences were identified that are 80-fold more actively transcribed than the initial library by E. coli RNA polymerase (RNAP). The selected motifs were found to be more active than canonical E. coli promoters in the same context. Experiments also demonstrated that a single-stranded pseudopromoter identified by this selection can be transplanted to other circular DNA contexts and retain transcriptional activity. Results suggest that the promoter is localized in a short ( approximately 40 nt) hairpin, which is smaller than canonical E. coli promoters. To test whether this pseudopromoter was active in bacterial cells, a synthetic DNA nanocircle vector encoding a ribozyme targeted to a site in the marA drug resistance gene was constructed to contain an optimized single-stranded promoter. It is shown that this DNA circle can act as a "Trojan horse" in E. coli, being actively transcribed by the cellular RNAP and producing ribozymes that cleave a sequence in the marA drug resistance gene. The use of optimized single-stranded promoters in combination with synthetic nanocircle DNA vectors represents a potentially useful way to engender the synthesis of biologically active RNAs in living cells.
| S-EPMC117513 | biostudies-literature
Project description:DNA replication initiation is mediated across all domains of life by initiator proteins oligomerizing at replication origins. Recently, it was shown that initiators can directly bind single-stranded DNA (ssDNA) and thus might enhance origin melting. In this study, we used single-molecule fluorescence assays to probe the ssDNA binding mechanism of the replication initiator DnaA. Our experiments revealed that DnaA forms a dynamic filament on ssDNA in 3' to 5' directionality in the presence of ATP and analogs. After nucleation with a three-monomer seed, monomers dynamically assemble and disassemble one monomer at a time at the 5' end, each monomer binding three nucleotides of ssDNA. The addition of adjacent double-stranded DnaA binding sites stabilized the DnaA filament on ssDNA. Our results extend the current models of origin melting via DnaA ssDNA interaction.
| S-EPMC4288177 | biostudies-literature
Project description:DNA replication is tightly controlled to ensure accurate inheritance of genetic information. In all organisms, initiator proteins possessing AAA+?(ATPases associated with various cellular activities) domains bind replication origins to license new rounds of DNA synthesis. In bacteria the master initiator protein, DnaA, is highly conserved and has two crucial DNA binding activities. DnaA monomers recognize the replication origin (oriC) by binding double-stranded DNA sequences (DnaA-boxes); subsequently, DnaA filaments assemble and promote duplex unwinding by engaging and stretching a single DNA strand. While the specificity for duplex DnaA-boxes by DnaA has been appreciated for over 30 years, the sequence specificity for single-strand DNA binding has remained unknown. Here we identify a new indispensable bacterial replication origin element composed of a repeating trinucleotide motif that we term the DnaA-trio. We show that the function of the DnaA-trio is to stabilize DnaA filaments on a single DNA strand, thus providing essential precision to this binding mechanism. Bioinformatic analysis detects DnaA-trios in replication origins throughout the bacterial kingdom, indicating that this element is part of the core oriC structure. The discovery and characterization of the novel DnaA-trio extends our fundamental understanding of bacterial DNA replication initiation, and because of the conserved structure of AAA+?initiator proteins these findings raise the possibility of specific recognition motifs within replication origins of higher organisms.
| S-EPMC4913881 | biostudies-literature
Project description:Regions of genomic DNA can become single-stranded in the course of normal replication and transcription as well as during DNA repair. Abnormal repair and replication intermediates can contain large stretches of persistent single-stranded DNA, which is extremely vulnerable to DNA damaging agents and hypermutation. Since such single-stranded DNA spans only a fraction of the genome at a given instance, hypermutation in these regions leads to tightly-spaced mutation clusters. This phenomenon of hypermutation in single-stranded DNA has been documented in several experimental models as well as in cancer genomes. Recently, hypermutated single-stranded RNA viral genomes also have been documented. Moreover, indications of hypermutation in single-stranded DNA may also be found in the human germline. This review will summarize key current knowledge and the recent developments in understanding the diverse mechanisms and sources of ssDNA hypermutation.
| S-EPMC7234795 | biostudies-literature