Novel Quinazoline Derivatives Inhibit Splicing of Fungal Group II Introns.

We report the discovery of small molecules that target the RNA tertiary structure of self-splicing group II introns and display potent antifungal activity against yeasts, including the major public health threat . High-throughput screening efforts against a yeast group II intron resulted in an inhibitor class which was then synthetically optimized for enhanced inhibitory activity and antifungal efficacy. The most highly refined compounds in this series display strong, gene-specific antifungal activity against .

Characterization and implementation of the MarathonRT template-switching reaction to expand the capabilities of RNA-seq.

End-to-end RNA-sequencing methods that capture 5'-sequence content without cumbersome library manipulations are of great interest, particularly for analysis of long RNAs. While template-switching methods have been developed for RNA sequencing by distributive short-read RTs, such as the MMLV RTs used in SMART-Seq methods, they have not been adapted to leverage the power of ultraprocessive RTs, such as those derived from group II introns. To facilitate this transition, we dissected the individual processes that guide the enzymatic specificity and efficiency of the multistep template-switching reaction carried out by RTs, in this case, by MarathonRT.

SARS-CoV-2-related bat viruses evade human intrinsic immunity but lack efficient transmission capacity.

Circulating bat coronaviruses represent a pandemic threat. However, our understanding of bat coronavirus pathogenesis and transmission potential is limited by the lack of phenotypically characterized strains. We created molecular clones for the two closest known relatives of SARS-CoV-2, BANAL-52 and BANAL-236.

The West Nile virus genome harbors essential riboregulatory elements with conserved and host-specific functional roles.

West Nile virus (WNV) is an arthropod-borne, positive-sense RNA virus that poses an increasing global threat due to warming climates and lack of effective therapeutics. Like other enzootic viruses, little is known about how host context affects the structure of the full-length RNA genome. Here, we report a complete secondary structure of the entire WNV genome within infected mammalian and arthropod cell lines.

Mechanism of Action of KL-50, a Candidate Imidazotetrazine for the Treatment of Drug-Resistant Brain Cancers.

Aberrant DNA repair is a hallmark of cancer, and many tumors display reduced DNA repair capacities that sensitize them to genotoxins. Here, we demonstrate that the differential DNA repair capacities of healthy and transformed tissue may be exploited to obtain highly selective chemotherapies. We show that the novel N3-(2-fluoroethyl)imidazotetrazine "KL-50" is a selective toxin toward tumors that lack the DNA repair protein O-methylguanine-DNA-methyltransferase (MGMT), which reverses the formation of O-alkylguanine lesions.

Nanoparticle Retinoic Acid-Inducible Gene 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 the response to immune checkpoint inhibitors (ICIs). However, the potency and clinical efficacy of 5'-triphosphate RNA (3pRNA) agonists of RIG-I are 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).

Covalent Polymer-RNA Conjugates for Potent Activation of the RIG-I Pathway.

RNA ligands of retinoic acid-inducible gene I (RIG-I) are a promising class of oligonucleotide therapeutics with broad potential as antiviral agents, vaccine adjuvants, and cancer immunotherapies. However, their translation has been limited by major drug delivery barriers, including poor cellular uptake, nuclease degradation, and an inability to access the cytosol where RIG-I is localized. Here this challenge is addressed by engineering nanoparticles that harness covalent conjugation of 5'-triphospate RNA (3pRNA) to endosome-destabilizing polymers.

Highly Reactive Group I Introns Ubiquitous in Pathogenic Fungi.

Systemic fungal infections are a growing public health threat, and yet viable antifungal drug targets are limited as fungi share a similar proteome with humans. However, features of RNA metabolism and the noncoding transcriptomes in fungi are distinctive. For example, fungi harbor highly structured RNA elements that humans lack, such as self-splicing introns within key housekeeping genes in the mitochondria.

A compact regulatory RNA element in mouse Hsp70 mRNA.

Hsp70 (70 kDa heat shock protein) performs molecular chaperone functions by assisting the folding of newly synthesized and misfolded proteins, thereby counteracting various cell stresses and preventing multiple diseases, including neurodegenerative disorders and cancers. It is well established that, immediately after heat shock, Hsp70 gene expression is mediated by a canonical mechanism of cap-dependent translation. However, the molecular mechanism of Hsp70 expression during heat shock remains elusive.

Structural insights into intron catalysis and dynamics during splicing.

The group II intron ribonucleoprotein is an archetypal splicing system with numerous mechanistic parallels to the spliceosome, including excision of lariat introns. Despite the importance of branching in RNA metabolism, structural understanding of this process has remained elusive. Here we present a comprehensive analysis of three single-particle cryogenic electron microscopy structures captured along the splicing pathway.

The E3 ligase Riplet promotes RIG-I signaling independent of RIG-I oligomerization.

RIG-I is an essential innate immune receptor that responds to infection by RNA viruses. The RIG-I signaling cascade is mediated by a series of post-translational modifications, the most important of which is ubiquitination of the RIG-I Caspase Recruitment Domains (CARDs) by E3 ligase Riplet. This is required for interaction between RIG-I and its downstream adapter protein MAVS, but the mechanism of action remains unclear.

End-to-end RT-PCR of long RNA and highly structured RNA.

RNA molecules play important roles in numerous normal cellular processes and disease states, from protein coding to gene regulation. RT-PCR, applying the power of polymerase chain reaction (PCR) to RNA by coupling reverse transcription with PCR, is one of the most important techniques to characterize RNA transcripts and monitor gene expression. The ability to analyze full-length RNA transcripts and detect their expression is critical to decipher their biological functions.

Making RNA: Using T7 RNA polymerase to produce high yields of RNA from DNA templates.

RNA is playing an ever-growing role in molecular biology and biomedicine due to the many ways it influences gene expression and its increasing use in modern therapeutics. Hence, production of RNA molecules in large quantity and high purity has become essential for advancing basic scientific research and for developing next-generation therapeutics. T7 RNA polymerase (RNAP) is a DNA-dependent RNA polymerase of bacteriophage origin and it is the most widely-utilized tool enzyme for producing RNA.

RT-based Sanger sequencing of RNAs containing complex RNA repetitive elements.

Although next-generation sequencing (NGS) technologies have revolutionized our ability to sequence DNA with high-throughput, the chain termination-based Sanger sequencing method remains a widely used approach for DNA sequence analysis due to its simplicity, low cost and high accuracy. In particular, high accuracy makes Sanger sequencing the "gold standard" for sequence validation in basic research and clinical applications. During the early days of Sanger sequencing development, reverse transcriptase (RT)-based RNA sequencing was also explored and showed great promise, but the approach did not acquire popularity over time due to the limited processivity and low template unwinding capability of Avian Myeloblastosis Virus (AMV) RT, and other RT enzymes available at the time.

The SMN complex drives structural changes in human snRNAs to enable snRNP assembly.

Spliceosomal snRNPs are multicomponent particles that undergo a complex maturation pathway. Human Sm-class snRNAs are generated as 3'-end extended precursors, which are exported to the cytoplasm and assembled together with Sm proteins into core RNPs by the SMN complex. Here, we provide evidence that these pre-snRNA substrates contain compact, evolutionarily conserved secondary structures that overlap with the Sm binding site.

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.

Discovery of Group II Intron RNA Splicing Inhibitors.

Here, we describe the discovery of compounds that inhibit self-splicing in group II introns. Using docking calculations, we targeted the catalytic active site within the group IIC intron and virtually screened a library of lead-like compounds. From this initial virtual screen, we identified three unique scaffolds that inhibit splicing .

Arena: Rapid and Accurate Reconstruction of Full Atomic RNA Structures From Coarse-grained Models.

RNA tertiary structures from experiments or computational predictions often contain missing atoms, which prevent analyses requiring full atomic structures. Current programs for RNA reconstruction can be slow, inaccurate, and/or require specific atoms to be present in the input. We present Arena (Atomic Reconstruction of RNA), which reconstructs a full atomic RNA structure from residues that can have as few as one atom.

rMSA: A Sequence Search and Alignment Algorithm to Improve RNA Structure Modeling.

The multiple sequence alignment (MSA) is the entry point of many RNA structure modeling tasks, such as prediction of RNA secondary structure (rSS) and contacts. However, there are few automated programs for generating high quality MSAs of target RNA molecules. We have developed rMSA, a hierarchical pipeline for sensitive search and accurate alignment of RNA homologs for a target RNA.

Systematic detection of tertiary structural modules in large RNAs and RNP interfaces by Tb-seq.

Compact RNA structural motifs control many aspects of gene expression, but we lack methods for finding these structures in the vast expanse of multi-kilobase RNAs. To adopt specific 3-D shapes, many RNA modules must compress their RNA backbones together, bringing negatively charged phosphates into close proximity. This is often accomplished by recruiting multivalent cations (usually Mg), which stabilize these sites and neutralize regions of local negative charge.

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.

PDC: a highly compact file format to store protein 3D coordinates.

Recent improvements in computational and experimental techniques for obtaining protein structures have resulted in an explosion of 3D coordinate data. To cope with the ever-increasing sizes of structure databases, this work proposes the Protein Data Compression (PDC) format, which compresses coordinates and temperature factors of full-atomic and Cα-only protein structures. Without loss of precision, PDC results in 69% to 78% smaller file sizes than Protein Data Bank (PDB) and macromolecular Crystallographic Information File (mmCIF) files with standard GZIP compression.

A protocol for capturing RNA-sensing innate immune receptors in multiple conformations by single-particle cryo-EM.

Capturing different conformations of receptor proteins that are complexed with ligands by single-particle cryo-EM facilitates our understanding toward the mechanisms of ligand recognition and receptor activation cascades. Here, we present a protocol for capturing RNA-sensing innate immune receptors, such as RIG-I, in multiple conformations by single-particle cryo-EM. We describe steps for protein-ligand sample preparation, data acquisition, and image processing covering focused three-dimensional classification.

A compact regulatory RNA element in mouse 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.

RSCanner: rapid assessment and visualization of RNA structure content.

Motivation: The increasing availability of RNA structural information that spans many kilobases of transcript sequence imposes a need for tools that can rapidly screen, identify, and prioritize structural modules of interest.

Results: We describe RNA Structural Content Scanner (RSCanner), an automated tool that scans RNA transcripts for regions that contain high levels of secondary structure and then classifies each region for its relative propensity to adopt stable or dynamic structures. RSCanner then generates an intuitive heatmap enabling users to rapidly pinpoint regions likely to contain a high or low density of discrete RNA structures, thereby informing downstream functional or structural investigation.