Biology subjects

Pyle, A. M.

Publications and source records attributed to Pyle, A. M..

At least 19 recordsLinked to original sources

bioRxiv2026

Immunomodulatory RIG-I Agonist SLR14 Confers Protection Against a Range of Highly Pathogenic Negative Sense RNA viruses

Emerging and re-emerging zoonotic RNA viruses, including filoviruses, henipaviruses and Rift Valley Fever virus (RVFV), pose a significant threat to human health. Due to their epidemic potential and high pathogenicity, these viruses are categorized as WHO priority pathogens, yet we still lack effective medical countermeasures (MCMs) against most of these dangerous pathogens, supporting that host-directed antivirals will be advantageous for broadly acting MCMs. Here we assessed the antiviral efficacy of SLR14, an immunomodulatory stem-loop RNA that activates RIG-I, for its activity against a panel of highly pathogenic viruses. SLR14 treatment provided broad-spectrum protection, markedly reducing infection with Ebola virus (EBOV), Marburg virus, and Sudan virus in human primary monocyte-derived macrophages, and Nipah virus replication in iPSC-derived endothelial cells, whether administered prophylactically or therapeutically. In vivo, a single dose of SLR14 protected mice against lethal RVFV infection when administered prophylactically, and, notably, retained significant efficacy when administered up to two days post-infection. Therapeutic SLR14 administration also improved survival rates of EBOV-infected mice. Although EBOV infection and SLR14 treatment activated overlapping innate immune pathways in human macrophages, viral infection induced a nonprotective response, whereas SLR14 elicited a well-regulated, markedly stronger and protective interferon-stimulated and inflammatory gene signature while avoiding prolonged IFN gene upregulation. Our data identify SLR14 as a potent host-directed therapeutic with broad antiviral efficacy against some of the most lethal viral pathogens.

microbiology↗

bioRxiv2026

Ebola virus mRNAs contain RNA structures that are critical for viral infection and targetable by antisense oligonucleotides

Filoviruses, such as Ebola virus (EBOV), are highly pathogenic non-segmented negative-sense RNA viruses (nsNSVs) with limited therapeutic options. Filovirus RNA structures remain largely untapped due to the enhanced biosafety requirements for handling infectious virus. Here, we present the first in-cell secondary structure maps of four EBOV mRNAs (VP35, VP40, VP30, and VP24) using two orthogonal chemical probing approaches: SHAPE-MaP and fbDMS-MaP. We find that EBOV mRNA coding sequences (CDS) are highly structured, much like +ssRNA viruses, whereas untranslated regions (UTRs) are significantly less structured. This suggests that high CDS structure contents are general features of viral translation templates, and that nsNSVs have evolved separate regulatory function at the RNA structure level that extends beyond using distinct mRNAs and genomes. These structure maps are consistent with formation of mRNA 5' hairpin structures during infection and reveal numerous additional RNA structures within the CDS, 3' UTRs, and at CDS-UTR junctions. To assess functionality, we disrupted these structures with locked nucleic acid (LNA) antisense oligonucleotides. Disrupting the TSS hairpins in VP35, VP30, and VP24 decreased infection by >60%, indicating these mRNA structures are critical for infection. LNA targeting of the newly identified structures reduced EBOV infection by 31% to 88%, thereby linking RNA structural integrity to viral function. Synonymous mutation rates and covariation analysis provided evolutionary support across mammalian filoviruses for the functional RNA elements observed. Collectively, these results demonstrate EBOV mRNAs contain numerous conserved RNA motifs contributing to viral infection, and that these elements represent promising targets for development of pan-filoviral therapeutics.

microbiology↗

bioRxiv2026

Heteromeric LGP2-MDA5 receptor complexes drive antiviral signaling

The innate immune receptor MDA5 serves as a first line of defense against RNA viruses by recognizing viral double-stranded RNA (dsRNA) and initiating antiviral signaling. MDA5 is upregulated by another RLR family member known as LGP2, which has been proposed to enhance MDA5 activity by recruiting MDA5 to dsRNA. However, it has remained unclear whether LGP2 functions solely as a transient recruitment factor or actively participates in signaling-competent MDA5 filaments. Here, we demonstrate that LGP2 does more than recruiting MDA5 to dsRNA, and that LGP2 becomes an integral component of MDA5 filaments. Mechanistically, LGP2 stabilizes MDA5 filaments and reduces the number of MDA5 molecules required to nucleate stable signaling-competent filaments. This interplay between the two RLR proteins is mediated by specific dsRNA-dependent interactions between the C-terminal tail of LGP2 and MDA5, resulting in a network of contacts that is essential for LGP2-mediated enhancement of MDA5 signaling. Together, these findings provide new mechanistic insight into how LGP2 regulates the assembly and persistence of signaling-competent MDA5 filaments, establishing filament architecture and stability as key determinants of MDA5 signaling. Collectively, this work provides a mechanistic framework for understanding LGP2-mediated regulation of MDA5 signaling and advances our knowledge of the molecular mechanisms governing antiviral immunity.

biochemistry↗

bioRxiv2026

Conserved structural features of the lncRNA HOTAIR in breast cancer cells

Long noncoding RNAs (lncRNAs) regulate diverse cellular processes and are frequently implicated in disease, but their functional mechanisms often remain elusive. One such lncRNA, HOTAIR (Hox transcript antisense intergenic RNA), is a [~]2.1 kb mammalian transcript whose overexpression promotes invasion and metastasis in breast cancer. However, the mechanisms by which HOTAIR influences gene regulation in cancer are poorly understood. To approach this problem through a structural lens, we determined the full-length in cellulo secondary structure of HOTAIR using chemical probing in a metastatic breast cancer cell line. The resulting structure shows that HOTAIR adopts a multidomain architecture and has local structural features unique to the cellular context. Comparison between in vitro and in cellulo chemical probing identifies regions of differential accessibility that may indicate context-dependent molecular interactions or folding. Conservation analyses further reveal that HOTAIR is conserved across primates with evidence of structural covariation in specific domains. Together, these results provide a roadmap for future mechanistic studies of structure-function relationships in HOTAIR and its contribution to gene regulation in cancer.

biochemistry↗

bioRxiv2026

Sequence alignment of the primate lineage reveals evolutionary divergence and conserved secondary structural motifs in noncoding RNAs

Long noncoding RNAs (lncRNAs) constitute most of the human transcriptome and perform essential roles in chromatin organization and transcriptional regulation. Because lncRNA genes are not constrained by protein-coding ability, they tend to exhibit more rapid evolutionary divergence. Their poor nucleotide sequence conservation among mammals often led to the assumption that lncRNAs lack conserved structures. However, emerging evidence indicates that many noncoding RNAs adopt secondary and tertiary folds critical for protein recruitment, chromatin binding, and regulation of gene expression. Nevertheless, there are few experimental secondary structures for lncRNAs, hindering mechanistic insight into lncRNA structure-function relationships. Even without available structural data, covariation, in which two nucleotides co-evolve, can provide evidence for conserved structures. This requires sequence alignments with sufficient divergence to detect covariation but enough similarity to maintain alignment quality. Here we report the development of a novel computational pipeline to mine 190 unannotated primate genomes to generate high-quality multiple sequence alignments of noncoding RNAs. This pipeline performs sequence searching, locus extraction, cross-species alignment, and downstream analyses, including assessment of covariation and primary sequence conservation. Ultimately, we demonstrate that because many noncoding elements, such as lncRNAs evolve at a more rapid rate than protein-coding genes, phylogenetic analyses constrained within a narrower evolutionary span can be used to identify conservation of primary sequence and secondary structure. By focusing our alignments on the primate lineage, our method overcomes the limitations of broad phylogenetic analyses, enabling high-resolution detection of subtle conservation patterns and conserved secondary structural motifs of long noncoding RNAs.

bioinformatics↗

bioRxiv2026

PCanPIE: A group I intron platform for efficient circRNA synthesis at ambient temperatures

Ribozyme-based permuted intron-exon (PIE) systems offer a protein-independent route to circRNA production, but existing platforms require elevated temperatures that promote RNA degradation. Here we report the first application of the Candida albicans mitochondrial large subunit (C.a.mtLSU) group I intron as a PIE platform for circRNA synthesis, which we term PCanPIE (Pyle lab Candida PIE). We evaluated three peripheral stems, P5, P6b, and P8, as permutation sites and demonstrated that all three support circularization under near-physiological conditions (25{degrees}C, 6 mM MgCl2), without the 55{degrees}C heating step required by existing PIE systems. Kinetic analysis revealed that permutation site does not affect the observed splicing rate constant but does influence PCanPIE folding and therefore influences circularization efficiency. The P6b permutation yielded the highest circularization efficiency, with 95 % of the precursor splicing to produce circRNA. Optimization of spacer sequences flanking the circRNA payload eliminated interference from structured native exon sequences and enabled efficient circularization of RNAs up to 1,657 nt, including structured, repetitive, and naturally occurring sequences. Together, these results establish PCanPIE as a versatile and near-physiologically active addition to the group I intron PIE toolkit.

biochemistry↗

bioRxiv2026

Interdependent RNA structural motifs at the 3'-terminus of the West Nile virus genome regulate viral growth

The RNA genome of West Nile Virus (WNV) folds into an elaborate series of RNA structural elements that are crucial for viral function. Among these elements, four pseudoknots (PKs) at the viral 3-terminus, designated as SLII, SLIV, DBI, and DBII, are among the most crucial players in the overall flaviviral lifecycle. While many studies have focused on exploring the behavior of individual PKs, we investigated the collective role of all four PKs in viral growth and small flaviviral RNA (sfRNA) formation. Through mutational analyses and infectious models, we establish that the four PKs are interdependent and work synergistically to aid in the folding and compaction of the WNV 3-terminal region. A striking hierarchy is observed in PK contributions to global folding and sfRNA formation, whereby SLIV plays the largest role, followed by DBI, DBII, and SLII. We also discover highly conserved RNA tertiary motifs within the PK assembly that are shared across flaviviruses, suggesting a new type of druggable target that may be of value in the search for pan-flaviviral therapeutics. GRAPHICAL ABSTRACT O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=63 SRC="FIGDIR/small/711107v1_ufig1.gif" ALT="Figure 1"> View larger version (17K): org.highwire.dtl.DTLVardef@14b10a5org.highwire.dtl.DTLVardef@131e63aorg.highwire.dtl.DTLVardef@1021aa9org.highwire.dtl.DTLVardef@12470a4_HPS_FORMAT_FIGEXP M_FIG C_FIG

biochemistry↗

bioRxiv2026

The long noncoding RNA Malat1 contains an internal ribosome entry site mediating micropeptide translation

In most cells, Malat1 long noncoding RNA localizes to the nucleus where it affects splicing and chromatin function. In neurons Malat1 is exported to the cytoplasm where it is translated to generate the M1 micropeptide. Here we characterize an internal ribosome entry site (IRES) required for Malat1 translation. Although preceded by a long Malat1 5' RNA segment this element induces translation at the M1 AUG. In vivo chemical probing and structural modeling identified a 135 nt RNA secondary structure consisting of three stem loops that is sufficient for IRES activity. Using this minimal element for affinity purification from cell extracts, the IRES RNA selectively binds ribosomal subunits and translation factors. Depletion of the binding proteins Rack1 and hnRNP A2/B1 inhibits downstream IRES-dependent translation without affecting translation of an upstream ORF. Our study identifies an unexpected functional unit hidden within a widely studied long noncoding RNA.

molecular biology↗

bioRxiv2026

RIG-I RNA agonist activates immunostimulatory macrophages to enhance checkpoint immunotherapy for glioblastoma

Glioblastoma (GBM), the most frequent and aggressive primary brain tumor, remains refractory to all current therapies including surgical resection, chemotherapy, radiotherapy and immunotherapy. Immunosuppressive mechanisms in the GBM tumor microenvironment contribute to the lack of anti-tumor adaptive immunity. We found that a subset of tumor associated macrophages (TAMs) can be repolarized into an anti-tumor phenotype via agonist stimulation of the retinoic acid-inducible gene I (RIGI), a cytosolic double-stranded RNA pattern recognition receptor (PRR). In silico analysis of adult GBM datasets available in the public domain revealed that RIGI expression by a subset of activated TAMs positively correlated with patient survival. Studies in syngeneic mouse models of GBM showed that intratumoral delivery of stem-loop RNA 14 (SLR14), a RIG-I agonist, improved the efficacy of chemotherapy, radiotherapy and immunotherapy treatments, beyond the effects of other nuclei acid sensor agonists. We found that RIGI+ macrophages are the main drivers of SLR14 effect, combining activation of TAMs and priming of functional cytotoxic CD8+ T lymphocytes and NK cells. The anti-GBM effect of SLR14 is opening a significant new avenue for adult GBM treatment.

cancer biology↗

bioRxiv2025

Single-cell RNA-seq using UltraMarathonRT expands theknown transcriptome

The ability to map messenger RNA (mRNA) molecules from individual cells using next-generation sequencing technologies, known as single-cell RNA-seq (scRNA-seq), is transforming biology by redefining cellular identities with unmatched detail. However, all current protocols depend on copying RNA into complementary DNA with a single reverse transcriptase (RT) derived from murine leukemia virus, which is an RT enzyme known for low processivity and limited ability to unfold complex RNA structures. Here, for the first time, we introduce a group II intron reverse transcriptase, UltraMarathonRT (uMRT), to perform scRNA-seq. We demonstrate that this enzyme reveals an unexpected transcriptomics landscape by capturing additional genes and other genomic features that conventional RTs miss. We also combined uMRT with metabolic RNA labeling, nucleoside conversion and scRNA-seq to explore genome-wide transcriptome dynamics at the single-cell level. Overall, we establish uMRT as a transformative biotechnological tool for single-cell transcriptomics.

molecular biology↗

bioRxiv2025

Structural basis for the function of long noncoding RNA Pnky in neural stem cells

LncRNA Pnky is a trans-acting regulator of neural stem cell (NSC) differentiation, but the molecular mechanisms by which Pnky regulates neurogenesis is unknown. A fundamental step towards mechanistic understanding is to determine whether a lncRNA has folded structure that underlies biological function. Using chemical probing and high-throughput analysis, we determined the secondary structure of Pnky folded in vitro and in cellulo. Pnky adopts a compact structure in vitro with distinct modules and evidence of tertiary interactions. In cellulo, Pnky structure is remarkably similar to the in vitro conformation. We used locked nucleic acid oligonucleotides to interrogate the entire Pnky transcript for function in NSCs and identified regions that when targeted increased neurogenesis - phenocopying Pnky knockdown - without decreasing transcript abundance. Our findings provide a structural basis for the role of Pnky in neurogenesis and, more broadly, illustrate how structural maps combined with phenotypic data can advance fundamental understanding of lncRNA mechanism. HIGHLIGHTSPnky folds into highly structured conformation in vitro with distinct modules. Pnky is a compact lncRNA with evidence of tertiary interactions. Pnky structure in neural stem cells is similar to its in vitro conformation. LNA ASO perturbations identify structured regions of Pnky involved in neuronal differentiation.

molecular biology↗

bioRxiv2023

Discovery of a Well-Folded Protein Interaction Hub Within the Human Long Non-Coding RNA NORAD

The long non-coding RNA NORAD functions in maintaining genomic stability in humans via sequestering Pumilio proteins from the cytoplasm, and thereby modulating the gene expression of mRNA targets of Pumilio proteins. Despite its role in fundamental cellular pathways including chromosome segregation and DNA damage response, there have been limited structural and biophysical descriptions of NORAD. Here, using an integrative approach combining chemical probing coupled to high throughput sequencing, and RNA-pull downs coupled with mass spectrometry, we discovered a well-folded and structured protein interaction hub within the functional core of NORAD. Our in vitro biochemical reconstitutions using purified recombinant proteins and a NORAD repeat unit region within this hub reveal the assembly of a higher-order multimeric RNA-protein complex.

molecular biology↗

bioRxiv2023

MRT-ModSeq - Rapid detection of RNA modifications with MarathonRT

Chemical modifications are essential regulatory elements that modulate the behavior and function of cellular RNAs. Despite recent advances in sequencing-based RNA modification mapping, methods combining accuracy and speed are still lacking. Here, we introduce MRT- ModSeq for rapid, simultaneous detection of multiple RNA modifications using MarathonRT. MRT-ModSeq employs distinct divalent cofactors to generate 2-D mutational profiles that are highly dependent on nucleotide identity and modification type. As a proof of concept, we use the MRT fingerprints of well-studied rRNAs to implement a general workflow for detecting RNA modifications. MRT-ModSeq rapidly detects positions of diverse modifications across a RNA transcript, enabling assignment of m1acp3Y, m1A, m3U, m7G and 2-OMe locations through mutation-rate filtering and machine learning. m1A sites in sparsely modified targets, such as MALAT1 and PRUNE1 could also be detected. MRT-ModSeq can be trained on natural and synthetic transcripts to expedite detection of diverse RNA modification subtypes across targets of interest.

biochemistry↗

bioRxiv2023

A Nanoparticle RIG-I Agonist for Cancer Immunotherapy

Pharmacological activation of the retinoic acid-inducible gene I (RIG-I) pathway holds promise for increasing tumor immunogenicity and improving response to immune checkpoint inhibitors (ICI). However, the potency and clinical efficacy of 5-triphosphate RNA (3pRNA) agonists of RIG-I is hindered by multiple pharmacological barriers, including poor pharmacokinetics, nuclease degradation, and inefficient delivery to the cytosol where RIG-I is localized. Here, we address these challenges through the design and evaluation of ionizable lipid nanoparticles (LNPs) for the delivery of 3p-modified stem-loop RNAs (SLRs). Packaging of SLRs into LNPs (SLR-LNPs) yielded surface charge-neutral nanoparticles with a size of [~]100 nm that activated RIG-I signaling in vitro and in vivo. SLR-LNPs were safely administered to mice via both intratumoral and intravenous routes, resulting in RIG-I activation in the tumor microenvironment (TME) and inhibition of tumor growth in mouse models of poorly immunogenic melanoma and breast cancer. Significantly, we found that systemic administration of SLR-LNPs reprogrammed the breast TME to enhance the infiltration of CD8+ and CD4+ T cells with antitumor function, resulting in enhanced response to PD-1 ICI in an orthotopic EO771 model of triple negative breast cancer. Therapeutic efficacy was further demonstrated in a metastatic B16.F10 melanoma model, with systemically administered SLR-LNPs significantly reducing lung metastatic burden compared to combined PD-1 + CTLA-4 ICI. Collectively, these studies have established SLR-LNPs as a translationally promising immunotherapeutic nanomedicine for potent and selective activation of RIG-I with potential to enhance response to ICIs and other immunotherapeutic modalities.

bioengineering↗

bioRxiv2023

A compact regulatory RNA element in human Hsp70 mRNA

Hsp70 performs molecular chaperone functions by assisting in folding newly synthesized or misfolded proteins, thereby counteracting various cell stresses and preventing multiple diseases including neurodegenerative disorders and cancer. It is well established that Hsp70 upregulation during post-heat shock stimulus is mediated by cap-dependent translation. However, the molecular mechanisms of Hsp70 expression during heat shock stimulus remains elusive, even though the 5 end of Hsp70 mRNA may form a compact structure to positively regulate protein expression in the mode of cap-independent translation. The minimal truncation which can fold to a compact structure was mapped and its secondary structure was characterized by chemical probing. The predicted model revealed a highly compact structure with multiple stems. Including the stem where the canonical start codon is located, several stems were identified to be vital for RNA folding, thereby providing solid structural basis for future investigations on the function of this RNA structure on Hsp70 translation during heat shock.

biochemistry↗

bioRxiv2022

US-align: Universal Structure Alignments of Proteins, Nucleic Acids, and Macromolecular Complexes

Structure comparison and alignment are of fundamental importance in structural biology studies. We developed the first universal platform, US-align, to uniformly align monomer and complex structures of different macromolecules (proteins, RNAs, and DNAs). The pipeline is built on a uniform TM-score objective function coupled with a heuristic alignment searching algorithm. Large-scale benchmarks demonstrated significant advantages of US-align over state-of-the-art methods in pairwise and multiple structure alignments of different molecules. Detailed analyses showed that the major advantage of US-align lies in the extensive optimization of the unified objective function powered by efficient heuristic search iterations, which significantly improve the accuracy and speed of the structural alignment process. Meanwhile, the universal protocol fusing different molecular and structural types helps facilitate the heterogeneous oligomer structure comparison and template-based protein-protein and protein-RNA/DNA docking.

bioinformatics↗

bioRxiv2021

A stem-loop RNA RIG-I agonist confers prophylactic and therapeutic protection against acute and chronic SARS-CoV-2 infection in mice

As SARS-CoV-2 continues to cause morbidity and mortality around the world, there is an urgent need for the development of effective medical countermeasures. Here, we assessed the antiviral capacity of a minimal RIG-I agonist, stem-loop RNA 14 (SLR14), in viral control, disease prevention, post-infection therapy, and cross-variant protection in mouse models of SARS-CoV-2 infection. A single dose of SLR14 prevented viral replication in the lower respiratory tract and development of severe disease in a type I interferon (IFN-I) dependent manner. SLR14 demonstrated remarkable protective capacity against lethal SARS-CoV-2 infection when used prophylactically and retained considerable efficacy as a therapeutic agent. In immunodeficient mice carrying chronic SARS-CoV-2 infection, SLR14 elicited near-sterilizing innate immunity by inducing IFN-I responses in the absence of the adaptive immune system. In the context of infection with variants of concern (VOC), SLR14 conferred broad protection and uncovered an IFN-I resistance gradient across emerging VOC. These findings demonstrate the therapeutic potential of SLR14 as a host-directed, broad-spectrum antiviral for early post-exposure treatment and for treatment of chronically infected immunosuppressed patients.

immunology↗

bioRxiv2021

Structural insights into the role of Dicer-related helicase 3 in RNAi in Caenorhabditis elegans.

DRH-3 belongs to the family of duplex RNA-dependent ATPases (DRAs), which include Dicer and RIG-I-like receptors (RLRs). DRH-3 is critically involved in germline development and RNAi-facilitated chromosome segregation via the 22G-siRNA pathway in C. elegans. The molecular understanding of DRH-3 and its function in endogenous RNAi pathways remains elusive. In this study, we solved the crystal structures of the DRH-3 N-terminal domain (NTD) and the C-terminal domains (CTDs) in complex with 5-triphosphorylated RNAs. The NTD of DRH-3 adopts a distinct fold of tandem Caspase Activation and Recruitment Domains (CARDs) structurally similar to the CARDs of RIG-I and MDA5, suggesting a signaling function in the endogenous RNAi biogenesis. The CTD preferentially recognizes 5-triphosphorylated double-stranded RNAs bearing the typical features of secondary siRNA transcripts. The full-length DRH-3 displays unique structural dynamics upon binding to RNA duplexes that differ from RIG-I or MDA5. These unique molecular features of DRH-3 help explain its function in RNAi in worms and the evolutionary divergence of the Dicer-like helicases.

biochemistry↗