Biology subjects

Borchert, G. M.

Publications and source records attributed to Borchert, G. M..

6 recordsLinked to original sources

bioRxiv2026

Conservation of Long G4-rich (LG4) genomic enhancer regulations

Long G4-rich regions (LG4s) are defined as DNA sequences containing a high density of guanine triplets capable of forming non-B DNA structures called G-quadruplexes (G4s). These regions frequently overlap with enhancers, which are regulatory DNA elements that modulate gene expression by interacting with DNA regions that dictate where transcription is initiated known as promoters. While LG4s have now been well-characterized in the human genome, neither LG4 occurrence, nor the ability of LG4s to function as enhancers, in other species has been described. To address this, we screened the genomes of 16 different species from various taxa to identify LG4s and then determined if they were conserved, and if so, if their regulatory capacity was similarly conserved. Our analyses characterized a number of previously unreported LG4s in the human genome as well as LG4s in 13 additional species. Of note, we identified a highly conserved LG4 enhancer predicted to regulate over 40 genes. This LG4 is embedded in the MAZ (Myc-Associated Zinc finger protein) locus, and we find this LG4 possesses the ability to directly interact with the same target promoter in both human and mouse. In summary, this work describes LG4s in the genomes of both unicellular and multicellular species including vertebrates, invertebrates, plants, and fungi. Furthermore, many of these LG4 sequences are highly conserved as is their regulatory capacity.

genomics↗

bioRxiv2024

Long G4-rich enhancer physically interacts with EXOC3 promoter via a G4:G4 DNA-based mechanism

Enhancers are genomic sequences that function as regulatory elements capable of increasing the transcription of a given gene often located at a considerable distance. The broadly accepted model of enhancer activation involves bringing an enhancer-bound activator protein complex into close spatial proximity to its target promoter through chromatin looping. Equally relevant to the work described herein, roles for guanine (G) rich sequences in transcriptional regulation are now widely accepted. Non-coding G-rich sequences are commonly found in gene promoters and enhancers, and various studies have described specific instances where G-rich sequences regulate gene expression via their capacity to form G-quadruplex (G4) structures under physiological conditions. In light of this, our group previously performed a search for long human genomic stretches significantly enriched for minimal G4 motifs (referred to as LG4s herein) leading to the identification of 301 LG4 loci with a density of at least 80 GGG repeats / 1,000 basepairs (bp) and averaging 1,843 bp in length. Further, in agreement with previous reports indicating that minimal G4s are highly enriched in promoters and enhancers, we found 217/301 LG4 sequences overlap a GeneHancer annotated enhancer, and the gene promoters regulated by these LG4 enhancers were found to be similarly, markedly enriched with G4-capable sequences. Importantly, while the generally accepted model for enhancer:promoter specificity maintains that interactions are dictated by enhancer- and promoter-bound transcriptional activator proteins, the current study was designed to test an alternative hypothesis: that LG4 enhancers physically interact with their cognate promoters via a direct G4:G4 DNA-based mechanism. As such, this work employs a combination of informatic mining and locus-specific immunoprecipitation strategies to establish the spatial proximity of enhancer:promoter pairs within the nucleus then biochemically confirms the ability of individual LG4 ssDNAs to directly and specifically interact with DNA sequences found in their target promoters. In addition, we also identify four single nucleotide polymorphisms (SNPs), occurring within a LG4 enhancer on human chromosome 5, significantly associated with Cystic Fibrosis (CF) lung disease severity (avg. p value = 2.83E-9), presumably due to their effects on the expressions of CF-relevant genes directly regulated by this LG4 enhancer (e.g., EXOC3 and CEP72). Graphical Abstract O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=121 SRC="FIGDIR/small/577212v1_ufig1.gif" ALT="Figure 1"> View larger version (23K): org.highwire.dtl.DTLVardef@1fee785org.highwire.dtl.DTLVardef@11f0a9org.highwire.dtl.DTLVardef@1cf198corg.highwire.dtl.DTLVardef@1963a55_HPS_FORMAT_FIGEXP M_FIG C_FIG In brief: LG4 enhancers physically interact with gene promoters by forming composite G4 structures where both the LG4 and cognate promoter contribute half of the necessary sequence for G4 formation.

genetics↗

bioRxiv2021

MicroRNA-like snoRNA-derived RNAs (sdRNAs) promote castration resistant prostate cancer

We have identified 38 specifically excised, differentially expressed snoRNA fragments (sdRNAs) in TCGA prostate cancer (PCa) patient samples as compared to normal prostate controls. SnoRNA-derived fragments sdRNA-D19b and -A24 emerged among the most differentially expressed and were selected for further experimentation. We found that overexpression of either sdRNA significantly increased PC3 (a well-established model of castration-resistant prostate cancer (CRPC)) cell proliferation, and that sdRNA-D19b overexpression also markedly increased the rate of PC3 cell migration. In addition, both sdRNAs provided drug-specific resistances with sdRNA-D19b levels correlating with paclitaxel resistance and sdRNA-24A conferring dasatinib resistance. In silico and in vitro analyses revealed that two established PCa tumor suppressor genes, CD44 and CDK12, represent targets for sdRNA-D19b and sdRNA-A24 respectively. This outlines a biologically coherent mechanism by which sdRNAs downregulate tumor suppressors in AR-PCa to enhance proliferative and metastatic capabilities and to encourage chemotherapeutic resistance. Aggressive proliferation, rampant metastasis, and recalcitrance to chemotherapy are core characteristics of CRPC that synergize to produce a pathology that ranks 2nd in cancer-related deaths for men. This study defines sdRNA-D19b and -A24 as contributors to AR-PCa potentially providing novel biomarkers and therapeutic targets of use in PCa clinical intervention.

cancer biology↗

bioRxiv2021

Salmonella Outer Membrane Vesicles contain tRNA Fragments (tRFs) that Inhibit Bacteriophage P22 infection

Salmonella Outer Membrane Vesicles (OMVs) were recently shown to inhibit P22 bacteriophage infection. Furthermore, despite there being several published reports now independently describing (1) the marked prevalence of tRFs within secreted vesicle transcriptomes and (2) roles for specific tRFs in facilitating/inhibiting viral replication, there have been no examinations of the effects of vesicle-secreted tRFs on viral infection reported to date. Notably, while specific tRFs have been reported in a number of bacteria, the tRFs expressed by salmonellae have not been previously characterized. As such, we recently screened small RNA-seq datasets for the presence of recurrent, specifically excised tRFs and identified 31 recurrent, relatively abundant tRFs expressed by Salmonella enterica serovar Typhimurium (SL1344). Whats more, we find S. Typhimurium OMVs contain significant levels of tRFs highly complementary to known Salmonella enterica-infecting bacteriophage with 17 of 31 tRFs bearing marked complementarity to at least one known Salmonella enterica-infecting phage (averaging 97.4% complementarity over 22.9 nt). Most notably, tRNA-Thr-CGT-1-1, 44-73, bears 100% sequence complementary over its entire 30 nt length to 29 distinct, annotated Salmonella enterica-infecting bacteriophage including P22. Importantly, we find inhibiting this tRF in secreted OMVs improves P22 infectivity in a dose dependent manner whereas raising OMV tRF levels conversely inhibits P22 infectivity. Furthermore, we find P22 phage pre-incubation with OMVs isolated from naive, control SL1344 S. Typhimurium, successfully rescues the ability of S. Typhimurium transformed with a specific tRNA-Thr-CGT-1-1, 44-73 tRF inhibitor to defend against P22. Collectively, these experiments confirm tRFs secreted in S. Typhimurium OMVs are directly involved with and required for the ability of OMVs to defend against bacteriophage predation. As we find the majority of OMV tRFs are highly complementary to an array of known Salmonella enterica-infecting bacteriophage, we suggest OMV tRFs may primarily function as a broadly acting, previously uncharacterized innate antiviral defense.

microbiology↗

bioRxiv2021

SALTS: SURFR (small noncoding RNA) And LAGOOn (long noncoding RNA) Transcriptomics Suite

The widespread utilization of high-throughput sequencing technologies has unequivocally demonstrated that eukaryotic transcriptomes consist primarily (>98%) of non-coding RNA (ncRNA) transcripts significantly more diverse than their protein-coding counterparts. ncRNAs are typically divided into two categories based on their length. (1) ncRNAs less than 200 nucleotides (nt) long are referred as small non-coding RNAs (sncRNAs) and include microRNAs (miRNAs), piwi-interacting RNAs (piRNAs), small nucleolar RNAs (snoRNAs), transfer ribonucleic RNAs (tRNAs), etc., and the majority of these are thought to function primarily in controlling gene expression. That said, the full repertoire of sncRNAs remains fairly poorly defined as evidenced by two entirely new classes of sncRNAs only recently being reported, i.e., snoRNA-derived RNAs (sdRNAs) and tRNA-derived fragments (tRFs). (2) ncRNAs longer than 200 nt long are known as long ncRNAs (lncRNAs). lncRNAs represent the 2nd largest transcriptional output of the cell (behind only ribosomal RNAs), and although functional roles for several lncRNAs have been reported, most lncRNAs remain largely uncharacterized due to a lack of predictive tools aimed at guiding functional characterizations. Importantly, whereas the cost of high-throughput transcriptome sequencing is now feasible for most active research programs, tools necessary for the interpretation of these sequencings typically require significant computational expertise and resources markedly hindering widespread utilization of these datasets. In light of this, we have developed a powerful new ncRNA transcriptomics suite, SALTS, which is highly accurate, markedly efficient, and extremely user-friendly. SALTS stands for SURFR (sncRNA) And LAGOOn (lncRNA) Transcriptomics Suite and offers platforms for comprehensive sncRNA and lncRNA profiling and discovery, ncRNA functional prediction, and the identification of significant differential expressions among datasets. Notably, SALTS is accessed through an intuitive Web-based interface, can be used to analyze either user-generated, standard next-generation sequencing (NGS) output file uploads (e.g., FASTQ) or existing NCBI Sequence Read Archive (SRA) data, and requires absolutely no dataset pre-processing or knowledge of library adapters/oligonucleotides. SALTS constitutes the first publically available, Web-based, comprehensive ncRNA transcriptomic NGS analysis platform designed specifically for users with no computational background, providing a much needed, powerful new resource capable of enabling more widespread ncRNA transcriptomic analyses. The SALTS WebServer is freely available online at http://salts.soc.southalabama.edu.

bioinformatics↗

bioRxiv2021

Characterization of 475 novel, putative small RNAs (sRNAs) in Carbon-starved Salmonella enterica serovar typhimurium

An increasingly apparent role of noncoding RNA (ncRNAs) is to coordinate gene expression when bacteria faces various environmental stressors. Salmonella enterica, a well-studied foodborne pathogen, is known for its ability to survive in and adapt to various environmental challenges, making it a difficult pathogen to eliminate, as well as an important model for examining ncRNA contributions to cellular stress survival. A mounting body of evidence implicates small RNAs (sRNAs) as key drivers of Salmonella stress response. Generally thought to be 50-500 nucleotides in length and to occur mainly in intergenic regions, sRNAs regulate protein expression through base pairing with mRNA targets. Through employing a refined definition of sRNAs that allows for shorter sequences and for sRNA loci to overlap with annotated protein-coding gene loci, we have identified 475 previously unannotated sRNAs that are significantly differentially expressed during Carbon starvation (C-starvation). Northern blotting and quantitative RT-PCRs confirm the expressions and identities of several of these novel sRNAs. Additionally, our computational analyses find the majority to be highly conserved and structurally-related to known sRNAs. Importantly, we show that deletion of one of the dynamic sRNAs, sRNA4130247, significantly impairs the Salmonella C-starvation response (CSR), confirming its involvement (and suggesting the involvements of many other sRNAs identified in this work) in the Salmonella CSR. Strikingly, the 475 novel sRNAs identified in this study more than double the number of Salmonella enterica serovar Typhimurium SL1344 sRNAs described to date, increasing the total number of annotated Salmonella sRNAs from 396 to 871. In conclusion, the work presented here provides the first-ever characterization of intragenic sRNAs in Salmonella, experimentally confirms that sRNAs dynamically expressed during the CSR are directly involved in stress survival, and strongly suggests that sRNA loci likely outnumber those of protein-coding genes in Salmonella.

microbiology↗