🧬 PubMed RNA Editing Daily Digest

RNA base editing using engineered deaminases represents a powerful tool to correct mutations at the RNA level. However, widespread off-target effects, primarily arising from dissociated free deaminases, remain a significant challenge. Here, we devise the RECODE (RNA editing with conditionally stable and enhanced ADAR1 deaminase variants) system, which employs designer degron-tagged ADAR1 deaminase (ADAR1d) with guide RNA (gRNA)-regulated stability. By promoting degradation of gRNA-unbound ADAR1d, RECODE markedly reduces transcriptome-wide edits while maintaining high on-target efficacy. Engineering gRNA for target RNA-induced conformational switching confines ADAR1d stabilization to intended editing sites, further enhancing editing precision. With structure-guided rational engineering of ADAR1d, RECODE efficiently corrects an Amyotrophic Lateral Sclerosis-relevant FUS mutation and installs a therapeutic mutation to Angptl3 in vivo, which mitigate FUS mislocalization to neuronal axons and lower plasma lipids, respectively. These findings establish RECODE as a highly stringent and efficient RNA editing technology and underscore a general principle for enhancing the specificity of RNA-guided protein effectors.

Achieving a single-molecule level for RNA detection remains a significant challenge in point-of-care settings. We present CCHP, a Cas13-Csm6-horseradish peroxidase three-step enzymatic cascade assay that enables amplification-free RNA detection with a simple colorimetric readout at 450 nm within 1 h under standard conditions. Across diverse viral and non-coding targets, CCHP spans a dynamic range of 10-10

Across biology, organisms have retained a mechanism to diversify the RNA transcriptome through RNA editing. Mediated by ADAR (adenosine deaminase acting on RNA) enzymes, Adenosines in double-stranded RNA (dsRNA) structures can be edited to Inosines (adenosine-to-inosine edit). Although this can change the amino acid sequence if it occurs in a coding sequence of mRNA, the majority of RNA editing in mammalian cells is found in noncoding repetitive elements. These repetitive elements have a predisposition to form long dsRNA structures that can mimic a dsRNA virus. Since the initial discoveries of RNA editing over 30 years ago, investigators have now identified ADAR1 to play a crucial role in suppressing innate immune activation and type I interferon signaling. Through adenosine-to-inosine editing, these dsRNA change their conformational structures and evade activation of the innate immune dsRNA sensor, MDA5. In human disease, although rare loss-of-function variants of ADAR1 have been associated with severe autoimmune disease, there has also been a rapid advance in our understanding of this molecular pathway in common complex diseases. We now understand that common genetic variants can impact RNA editing frequencies, and variants that decrease RNA editing are associated with an increase in risk of numerous autoinflammatory disorders as well as coronary artery disease. This rapid advance in our understanding of the genetic determinants of RNA editing and coronary artery disease has been mirrored by new discoveries in molecular biology, where deficient RNA editing within the vascular wall and smooth muscle cell now highlights endogenous RNA sensing by MDA5 as a causal mechanism of coronary artery disease and other vascular disorders. Here, in this review, we provide a focused look at major advances in RNA editing and cardiovascular disease and put these discoveries into historical context with a goal to map the next steps to advance these molecular pathways to new therapeutic discovery.

Deamination of adenosine to inosine (A-to-I) in double-stranded microRNAs (miRNAs) has been demonstrated to affect their function as suppressors or oncogenes in various cancers. Nevertheless, the functional impact of miRNA editing in high-grade serous ovarian cancer (HGSOC) remains largely unexplored. Here, we identified A-to-I editing in miRNAs in 60 HGSOC tissues and 48 ovarian tissues received in nononcological procedures using small RNA sequencing (RNA-Seq). To investigate the functional impact of A-to-I modifications, we tested the effect of edited RNA mimics and small interfering RNA (siRNA)-mediated downregulation of the RNA-editing enzyme double-stranded RNA-specific editase Adar (ADAR1) on cell proliferation, migration and three-dimensional (3D) growth of HGSOC cells in vitro. Tumour suppressor miR-200b-3p was the most overedited miRNA in HGSOC tumours, and the increased editing level was associated with statistically significant worse overall survival (OS). Mechanistically, in contrast to wild-type miRNA, edited miR-200b-3p promoted cell proliferation, migration and formation of 3D spheroids. Loss of function of ADAR1 profoundly repressed proliferation, migration and 3D growth of HGSOC cells. RNA-Seq and Gene Set Enrichment Analysis (GSEA) analysis revealed that, whereas wild-type miR-200b-3p induced the apoptosis pathway, edited miR-200b-3p substantially inhibited cell-cycle-related pathways. Bioinformatic prediction revealed that edited miR-200b-3p gained the function to repress the expression of new targets, including tumour suppressor MAX interactor 1, dimerisation protein (MXI1), which was associated with a statistically significantly worse OS time in HGSOC patients. Our study reports the potential contribution of edited miR-200b-3p in HGSOC progression, and highlights its potential as a new therapeutic target.

Transposable elements (TEs) threaten genomic integrity, yet their pervasive presence indicates the limitations of existing silencing mechanisms. A recent paper in