A reference catalog of DNA palindromes in the human genome and their variations in 1000 Genomes

Identifying Safeguards Disabled by Epstein-Barr Virus Infections in Genomes From Patients With Breast Cancer: Chromosomal Bioinformatics Analysis

Background

The causes of breast cancer are poorly understood. A potential risk factor is Epstein-Barr virus (EBV), a lifelong infection nearly everyone acquires. EBV-transformed human mammary cells accelerate breast cancer when transplanted into immunosuppressed mice, but the virus can disappear as malignant cells reproduce. If this model applies to human breast cancers, then they should have genome damage characteristic of EBV infection.

Objective

This study tests the hypothesis that EBV infection predisposes one to breast cancer by causing permanent genome damage that compromises cancer safeguards.

Methods

Publicly available genome data from approximately 2100 breast cancers and 25 ovarian cancers were compared to cancers with proven associations to EBV, including 70 nasopharyngeal cancers, 90 Burkitt lymphomas, 88 diffuse large B-cell lymphomas, and 34 gastric cancers. Calculation algorithms to make these comparisons were developed.

Results

Chromosome breakpoints in breast and ovarian cancer clustered around breakpoints in EBV-associated cancers. Breakpoint distributions in breast and EBV-associated cancers on some chromosomes were not confidently distinguished (P>.05), but differed from controls unrelated to EBV infection. Viral breakpoint clusters occurred in high-risk, sporadic, and other breast cancer subgroups. Breakpoint clusters disrupted gene functions essential for cancer protection, which remain compromised even if EBV infection disappears. As CRISPR (clustered regularly interspaced short palindromic repeats)-like reminders of past infection during evolution, EBV genome fragments were found regularly interspaced between Piwi-interacting RNA (piRNA) genes on chromosome 6. Both breast and EBV-associated cancers had inactivated genes that guard piRNA defenses and the major histocompatibility complex (MHC) locus. Breast and EBV-associated cancer breakpoints and other variations converged around the highly polymorphic MHC. Not everyone develops cancer because MHC differences produce differing responses to EBV infection. Chromosome shattering and mutation hot spots in breast cancers preferentially occurred at incorporated viral sequences. On chromosome 17, breast cancer breakpoints that clustered around those in EBV-mediated cancers were linked to estrogen effects. Other breast cancer breaks affected sites where EBV inhibits JAK-STAT and SWI-SNF signaling pathways. A characteristic EBV-cancer gene deletion that shifts metabolism to favor tumors was also found in breast cancers. These changes push breast cancer into metastasis and then favor survival of metastatic cells.

Conclusions

EBV infection predisposes one to breast cancer and metastasis, even if the virus disappears. Identifying this pathogenic viral damage may improve screening, treatment, and prevention. Immunizing children against EBV may protect against breast, ovarian, other cancers, and potentially even chronic unexplained diseases.

Causal relationships between immune cells, inflammatory cytokines, and pertussis: Bidirectional 2-sample Mendelian randomization study and mediation analysis

Studies have shown that immune cells play an important role in the occurrence and development of pertussis, but the specific causal relationships are yet to be determined. Additionally, inflammatory cytokines, as regulators of immune responses, may mediate the relationship between immune cells and pertussis, and the specific mechanisms involved require further exploration. This study utilizes data from multiple large-scale genome-wide association studies, covering 731 types of immune cells and 91 types of inflammatory cytokines. The bidirectional 2-sample Mendelian randomization (MR) method is employed, with inverse-variance weighted as the main statistical approach, to assess the causal relationships between immune cells, inflammatory cytokines, and pertussis. Furthermore, a 2-step MR method is used to investigate the mediating role of inflammatory cytokines in the effect of immune cells on pertussis. Our study results indicate that 11 types of immune cells have a protective effect against pertussis, with the strongest protection observed from CD25 on CD28+ CD4+ cells (OR = 0.3533, CI = 0.1636-0.7627, P = .008). Conversely, 19 types of immune cells are positively associated with the risk of pertussis, with the strongest correlation found in CD3- lymphocyte %lymphocyte (OR = 3.6613, CI = 1.5012-8.299, P = .0043). Additionally, 3 inflammatory cytokines - IL-4, IL-18R1, and FGF-21 - show a causal relationship with pertussis. Our mediation MR results indicate that inflammatory cytokines do not act as mediators in the relationship between immune cells and pertussis. This study suggests a causal relationship between immune cells and pertussis, while inflammatory cytokines do not appear to be mediating factors in the pathway from immune cells to pertussis.

Whole genome regulatory effect of MoISW2 and consequences for the evolution of the rice plant pathogenic fungus Magnaporthe oryzae

Isw2 proteins, ubiquitous across eukaryotes, exhibit a propensity for DNA binding and exert dynamic influences on local chromosome condensation in an ATP-dependent fashion, thereby modulating the accessibility of neighboring genes to transcriptional machinery. Here, we report the deletion of a putative MoISW2 gene, yielding substantial ramifications on plant pathogenicity. Subsequent gene complementation and chromatin immunoprecipitation sequencing (ChIP-seq) analyses were conducted to delineate binding sites. RNA sequencing (RNA-seq) assays revealed discernible impacts on global gene regulation along chromosomes in both mutant and wild-type strains, with comparative analyses against 55 external RNA-seq data sets corroborating these findings. Notably, MoIsw2-mediated binding and activities delineate genomic loci characterized by pronounced gene expression variability proximal to MoIsw2 binding sites, juxtaposed with comparatively stable expression in surrounding regions. The contingent genes influenced by MoIsw2 activity predominantly encompass niche-determinant genes, including those encoding secreted proteins, secondary metabolites, and stress-responsive elements, alongside avirulence genes. Furthermore, our investigations unveil a spatial correlation between MoIsw2 binding motifs and known transposable elements (TEs), suggesting a potential interplay wherein TE transposition at these loci could modulate the transcriptional landscape of Magnaporthe oryzae in a strain-specific manner. Collectively, these findings position MoIsw2 as a plausible master regulator orchestrating the delicate equilibrium between genes vital for biomass proliferation, akin to housekeeping genes, and niche-specific determinants crucial for ecological adaptability. Stress-induced TE transposition, in conjunction with MoIsw2 activity, emerges as a putative mechanism fostering enhanced mutagenesis and accelerated evolution of niche-determinant genes relative to housekeeping counterparts.IMPORTANCEIsw2 proteins are conserved in plants, fungi, animals, and other eukaryotes. We show that a fungal Isw2 protein in the rice pathogen Magnaporthe oryzae binds to retrotransposon (RT) DNA motifs and affects the epigenetic gene expression landscape of the fungal genome. Mainly ecological niche determinant genes close to the binding motifs are affected. RT elements occur frequently in DNA between genes in most organisms. They move place and multiply in the genome, especially under physiological stress. We further discuss the Isw2 and RT combined activities as a possible sought-after mechanism that can cause biased mutation rates and faster evolution of genes necessary for reacting to abiotic and biotic challenges. The most important biotic challenges for plant pathogens are the ones from the host plants' innate immunity. The overall result of these combined activities will be an adaptation-directed evolution of niche-determinant genes.

Impact of Gut Microbiota and Inflammatory Cytokines on Immune Thrombocytopenia

Immune thrombocytopenic purpura (ITP) is an autoimmune disorder, and recent research suggests that gut microbiota and inflammatory cytokines may play a significant role in its pathogenesis. However, the specific effects of these factors on ITP and their relationships remain unclear. We conducted a two-step, two-sample Mendelian randomization study using an inverse variance-weighted approach to investigate the causal role of the gut microbiota in ITP and the mediating effect of inflammatory cytokines on their association. The results showed that among the 473 gut microbiota species, 11 were positively associated and 12 were negatively associated with the risk of ITP. Among the 91 screened inflammatory cytokines, five (CXCL10, CXCL5, IL-12RA, TRAIL, and VEGF-A) were found to have a causal relationship with ITP. Mediation analysis revealed that the gut microbiota UBA1066 promoted the occurrence of ITP through CXCL10 mediation, with a mediation effect of 0.118932 (95% CI: 0.049471-0.188393) accounting for 9.95% of the total effect. Gut microbiota Treponema promoted ITP through VEGF-A mediation, with a mediation effect of 0.045873 (95% CI: 0.01456-0.07718) accounting for 4.28% of the total effect. Gut microbiota Haloplasma promoted the occurrence of ITP via CXCL5. The mediating effect of CXCL5 was 0.038409 (95% CI = 0.00107718-0.07575082), with a mediating ratio of 16.79%. This study revealed a causal relationship between gut microbiota composition and ITP risk, highlighting three inflammatory cytokines as potential causal mediators of this relationship. These findings provide potential targets and biomarkers for the prevention and treatment of ITP with significant clinical implications.

Optical Genome Mapping Identifies a Second Xq27.1 Rearrangement Associated With Charcot-Marie-Tooth Neuropathy CMTX3

BACKGROUND

X-linked recessive type 3 Charcot-Marie-Tooth (CMTX3) is a rare subtype of childhood-onset CMT. To date, all reported CMTX3 patients share a common founder 78 kb insertion from chromosome 8 into the Xq27.1 palindrome region.

METHODS

We conducted patient-parent trio optical genome mapping (OGM) on a male patient presenting with clinically diagnosed Dejerine-Sottas disease for whom initial standard diagnostic genetic tests, including whole-genome sequencing (WGS), yielded negative results.

RESULTS

OGM analysis revealed a maternally inherited interchromosomal insertion from chromosome region 7q31.1 into Xq27.1. Coupled with manual reassessment of WGS data, this confirmed the molecular diagnosis of atypical CMTX3 and showed that the 122.4 kb inserted fragment contained DLD and partially LAMB1. Subsequent analyses confirmed that the rearrangement had arisen de novo in the proband's mother.

CONCLUSION

We report the second Xq27.1 rearrangement associated with CMTX3, providing novel clinical insights into its phenotypic and genotypic spectrum. Our findings highlight the importance of including genomic rearrangement analysis of Xq27.1 in standard diagnostic pipelines for childhood-onset CMT. Given the overlap in polyneuropathy phenotypes resulting from insertions from chromosomes 7 and 8 into the same Xq27.1 palindrome region, the pathogenic mechanism underlying peripheral neuropathy in CMTX3 likely involves dysregulation of genes within this region.

Unraveling the complexity: Advanced methods in analyzing DNA, RNA, and protein interactions

Exploring the intricate interplay within and between nucleic acids, as well as their interactions with proteins, holds pivotal significance in unraveling the molecular complexities steering cancer initiation and progression. To investigate these interactions, a diverse array of highly specific and sensitive molecular techniques has been developed. The selection of a particular technique depends on the specific nature of the interactions. Typically, researchers employ an amalgamation of these different techniques to obtain a comprehensive and holistic understanding of inter- and intramolecular interactions involving DNA-DNA, RNA-RNA, DNA-RNA, or protein-DNA/RNA. Examining nucleic acid conformation reveals alternative secondary structures beyond conventional ones that have implications for cancer pathways. Mutational hotspots in cancer often lie within sequences prone to adopting these alternative structures, highlighting the importance of investigating intra-genomic and intra-transcriptomic interactions, especially in the context of mutations, to deepen our understanding of oncology. Beyond these intramolecular interactions, the interplay between DNA and RNA leads to formations like DNA:RNA hybrids (known as R-loops) or even DNA:DNA:RNA triplex structures, both influencing biological processes that ultimately impact cancer. Protein-nucleic acid interactions are intrinsic cellular phenomena crucial in both normal and pathological conditions. In particular, genetic mutations or single amino acid variations can alter a protein's structure, function, and binding affinity, thus influencing cancer progression. It is thus, imperative to understand the differences between wild-type (WT) and mutated (MT) genes, transcripts, and proteins. The review aims to summarize the frequently employed methods and techniques for investigating interactions involving nucleic acids and proteins, highlighting recent advancements and diverse adaptations of each technique.

Enhancing the Features of DNA Mimic Foldamers for Structural Investigations

DNA mimic foldamers based on aromatic oligoamide helices bearing anionic phosphonate side chains have been shown to bind to DNA-binding proteins sometimes orders of magnitude better than DNA itself. Here, we introduce new features in the DNA mimic foldamers to facilitate structural investigations of their interactions with proteins. Thirteen new foldamer sequences have been synthesized and characterized using NMR, circular dichroism, molecular modeling, and X-ray crystallography. The results show that foldamer helix handedness can be quantitatively biased by means of a single stereogenic center, that the foldamer structure can be made C2-symmetrical as in palindromic B-DNA sequences, and that associations between foldamer helices can be promoted utilizing dedicated C-terminal residues that act as sticky ends in B-DNA structures.

A Practical Approach for Targeting Structural Variants Genome-wide in Plasma Cell-free DNA

Plasma cell-free DNA (cfDNA) is a promising source of gene mutations for cancer detection by liquid biopsy. However, no current tests interrogate chromosomal structural variants (SVs) genome-wide. Here, we report a simple molecular and sequencing workflow called Genome-wide Analysis of Palindrome Formation (GAPF-seq) to probe DNA palindromes, a type of SV that often demarcates gene amplification. With low-throughput next-generation sequencing and automated machine learning, tumor DNA showed skewed chromosomal distributions of high-coverage 1-kb bins (HCBs), which differentiated 39 breast tumors from matched normal DNA with an average Area Under the Curve (AUC) of 0.9819. A proof-of-concept liquid biopsy study using cfDNA from prostate cancer patients and healthy individuals yielded an average AUC of 0.965. HCBs on the X chromosome emerged as a determinant feature and were associated with androgen receptor gene amplification. As a novel agnostic liquid biopsy approach, GAPF-seq could fill the technological gap offering unique cancer-specific SV profiles.

A Practical Approach for Targeting Structural Variants Genome-wide in Plasma Cell-free DNA

Interrogating plasma cell-free DNA (cfDNA) to detect cancer offers promise; however, no current tests scan structural variants (SVs) throughout the genome. Here, we report a simple molecular workflow to enrich a tumorigenic SV (DNA palindromes/fold-back inversions) that often demarcates genomic amplification and its feasibility for cancer detection by combining low-throughput next-generation sequencing with automated machine learning (Genome-wide Analysis of Palindrome Formation, GAPF-seq). Tumor DNA signal manifested as skewed chromosomal distributions of high-coverage 1-kb bins (HCBs), differentiating 39 matched breast tumor DNA from normal DNA with an average AUC of 0.9819. In a proof-of-concept liquid biopsy study, cfDNA from 0.5 mL plasma from prostate cancer patients was sufficient for binary classification against matched buffy coat DNA with an average AUC of 0.965. HCBs on the X chromosome emerged as a determinant feature and were associated with AR amplification. GAPF-seq could generate unique cancer-specific SV profiles in an agnostic liquid biopsy setting.

A unifying model that explains the origins of human inverted copy number variants

With the release of the telomere-to-telomere human genome sequence and the availability of both long-read sequencing and optical genome mapping techniques, the identification of copy number variants (CNVs) and other structural variants is providing new insights into human genetic disease. Different mechanisms have been proposed to account for the novel junctions in these complex architectures, including aberrant forms of DNA replication, non-allelic homologous recombination, and various pathways that repair DNA breaks. Here, we have focused on a set of structural variants that include an inverted segment and propose that they share a common initiating event: an inverted triplication with long, unstable palindromic junctions. The secondary rearrangement of these palindromes gives rise to the various forms of inverted structural variants. We postulate that this same mechanism (ODIRA: origin-dependent inverted-repeat amplification) that creates the inverted CNVs in inherited syndromes also generates the palindromes found in cancers.

Gut microbiota and sepsis: bidirectional Mendelian study and mediation analysis

Background

There is a growing body of evidence that suggests a connection between the composition of gut microbiota and sepsis. However, more research is needed to better understand the causal relationship between the two. To gain a deeper insight into the association between gut microbiota, C-reactive protein (CRP), and sepsis, we conducted several Mendelian randomization (MR) analyses.

Methods

In this study, publicly available genome-wide association study (GWAS) summary statistics were examined to determine the correlation between gut microbiota and sepsis, including various sepsis subgroups (such as under 75, 28-day death, Critical Care Units (ICU), 28-day death in ICU). Initially, two-sample and reverse Mendelian randomization (MR) analyses were conducted to identify causality between gut microbiota and sepsis. Subsequently, multivariable and two-step MR analyses revealed that the relationship between microbiota and sepsis was mediated by CRP. The robustness of the findings was confirmed through several sensitivity analyses.

Findings

In our study, we revealed positive correlations between 24 taxa and different sepsis outcomes, while 30 taxa demonstrated negative correlations with sepsis outcomes. Following the correction for multiple testing, we found that the Phylum Lentisphaerae (OR: 0.932, p = 2.64E-03), class Lentisphaeria, and order Victivallales (OR: 0.927, p = 1.42E-03) displayed a negative relationship with sepsis risk. In contrast, Phylum Tenericutes and class Mollicutes (OR: 1.274, p = 2.89E-03) were positively related to sepsis risk and death within 28 days. It is notable that Phylum Tenericutes and class Mollicutes (OR: 1.108, p = 1.72E-03) also indicated a positive relationship with sepsis risk in individuals under 75. From our analysis, it was shown that C-reactive protein (CRP) mediated 32.16% of the causal pathway from Phylum Tenericutes and class Mollicutes to sepsis for individuals under 75. Additionally, CRP was found to mediate 31.53% of the effect of the genus Gordonibacter on sepsis. Despite these findings, our reverse analysis did not indicate any influence of sepsis on the gut microbiota and CRP levels.

Conclusion

The study showcased the connection between gut microbiota, CRP, and sepsis, which sheds new light on the potential role of CRP as a mediator in facilitating the impact of gut microbiota on sepsis.

Distinguishing Genetic Drift from Selection in Papillomavirus Evolution

Pervasive purifying selection on non-synonymous substitutions is a hallmark of papillomavirus genome history, but the role of selection on and the drift of non-coding DNA motifs on HPV diversification is poorly understood. In this study, more than a thousand complete genomes representing Alphapapillomavirus types, lineages, and SNP variants were examined phylogenetically and interrogated for the number and position of non-coding DNA sequence motifs using Principal Components Analyses, Ancestral State Reconstructions, and Phylogenetic Independent Contrasts. For anciently diverged Alphapapillomavirus types, composition of the four nucleotides (A, C, G, T), codon usage, trimer usage, and 13 established non-coding DNA sequence motifs revealed phylogenetic clusters consistent with genetic drift. Ancestral state reconstruction and Phylogenetic Independent Contrasts revealed ancient genome alterations, particularly for the CpG and APOBEC3 motifs. Each evolutionary analytical method we performed supports the unanticipated conclusion that genetic drift and different evolutionary drivers have structured Alphapapillomavirus genomes in distinct ways during successive epochs, even extending to differences in more recently formed variant lineages.

Widely spaced and divergent inverted repeats become a potent source of chromosomal rearrangements in long single-stranded DNA regions

DNA inverted repeats (IRs) are widespread across many eukaryotic genomes. Their ability to form stable hairpin/cruciform secondary structures is causative in triggering chromosome instability leading to several human diseases. Distance and sequence divergence between IRs are inversely correlated with their ability to induce gross chromosomal rearrangements (GCRs) because of a lesser probability of secondary structure formation and chromosomal breakage. In this study, we demonstrate that structural parameters that normally constrain the instability of IRs are overcome when the repeats interact in single-stranded DNA (ssDNA). We established a system in budding yeast whereby >73 kb of ssDNA can be formed in cdc13-707fs mutants. We found that in ssDNA, 12 bp or 30 kb spaced Alu-IRs show similarly high levels of GCRs, while heterology only beyond 25% suppresses IR-induced instability. Mechanistically, rearrangements arise after cis-interaction of IRs leading to a DNA fold-back and the formation of a dicentric chromosome, which requires Rad52/Rad59 for IR annealing as well as Rad1-Rad10, Slx4, Msh2/Msh3 and Saw1 proteins for nonhomologous tail removal. Importantly, using structural characteristics rendering IRs permissive to DNA fold-back in yeast, we found that ssDNA regions mapped in cancer genomes contain a substantial number of potentially interacting and unstable IRs.

Multiple regulatory mechanisms for pH homeostasis in the gastric pathogen, Helicobacter pylori

Acid-resistance in gastric pathogen Helicobacter pylori requires the coordination of four essential processes to regulate urease activity. Firstly, urease expression above a base level needs to be finely tuned at different ambient pH. Secondly, as nickel is needed to activate urease, nickel homeostasis needs to be maintained by proteins that import and export nickel ions, and sequester, store and release nickel when needed. Thirdly, urease accessary proteins that activate urease activity by nickel insertion need to be expressed. Finally, a reliable source of urea needs to be maintained by both intrinsic and extrinsic sources of urea. Two-component systems (arsRS and flgRS), as well as a nickel response regulator (NikR), sense the change in pH and act on a variety of genes to accomplish the function of acid resistance without causing cellular overalkalization and nickel toxicity. Nickel storage proteins also feature built-in switches to store nickel at neutral pH and release nickel at low pH. This review summarizes the current status of H. pylori research and highlights a number of hypotheses that need to be tested.

Interaction of Proteins with Inverted Repeats and Cruciform Structures in Nucleic Acids

Cruciforms occur when inverted repeat sequences in double-stranded DNA adopt intra-strand hairpins on opposing strands. Biophysical and molecular studies of these structures confirm their characterization as four-way junctions and have demonstrated that several factors influence their stability, including overall chromatin structure and DNA supercoiling. Here, we review our understanding of processes that influence the formation and stability of cruciforms in genomes, covering the range of sequences shown to have biological significance. It is challenging to accurately sequence repetitive DNA sequences, but recent advances in sequencing methods have deepened understanding about the amounts of inverted repeats in genomes from all forms of life. We highlight that, in the majority of genomes, inverted repeats are present in higher numbers than is expected from a random occurrence. It is, therefore, becoming clear that inverted repeats play important roles in regulating many aspects of DNA metabolism, including replication, gene expression, and recombination. Cruciforms are targets for many architectural and regulatory proteins, including topoisomerases, p53, Rif1, and others. Notably, some of these proteins can induce the formation of cruciform structures when they bind to DNA. Inverted repeat sequences also influence the evolution of genomes, and growing evidence highlights their significance in several human diseases, suggesting that the inverted repeat sequences and/or DNA cruciforms could be useful therapeutic targets in some cases.

Ultrasensitive electrochemical aptasensor based on palindromic sequence mediated bidirectional SDA and a DNAzyme walker for kanamycin detection

An electrochemical biosensing platform for kanamycin analysis based on SDA and a DNA walker.

Concatenation of Transgenic DNA: Random or Orchestrated?

Generation of transgenic organisms by pronuclear microinjection has become a routine procedure. However, while the process of DNA integration in the genome is well understood, we still do not know much about the recombination between transgene molecules that happens in the first moments after DNA injection. Most of the time, injected molecules are joined together in head-to-tail tandem repeats-the so-called concatemers. In this review, we focused on the possible concatenation mechanisms and how they could be studied with genetic reporters tracking individual copies in concatemers. We also discuss various features of concatemers, including palindromic junctions and repeat-induced gene silencing (RIGS). Finally, we speculate how cooperation of DNA repair pathways creates a multicopy concatenated insert.

Palindromes in DNA-A Risk for Genome Stability and Implications in Cancer

A palindrome in DNA consists of two closely spaced or adjacent inverted repeats. Certain palindromes have important biological functions as parts of various cis-acting elements and protein binding sites. However, many palindromes are known as fragile sites in the genome, sites prone to chromosome breakage which can lead to various genetic rearrangements or even cell death. The ability of certain palindromes to initiate genetic recombination lies in their ability to form secondary structures in DNA which can cause replication stalling and double-strand breaks. Given their recombinogenic nature, it is not surprising that palindromes in the human genome are involved in genetic rearrangements in cancer cells as well as other known recurrent translocations and deletions associated with certain syndromes in humans. Here, we bring an overview of current understanding and knowledge on molecular mechanisms of palindrome recombinogenicity and discuss possible implications of DNA palindromes in carcinogenesis. Furthermore, we overview the data on known palindromic sequences in the human genome and efforts to estimate their number and distribution, as well as underlying mechanisms of genetic rearrangements specific palindromic sequences cause.