Extracellular N6 -isopentenyladenosine (i6A) addition induces cotranscriptional i6A incorporation into ribosomal RNAs

Discovery of Photoexcited 2-Chloro-3,5-Dinitrobenzoic Acid as a Chemical Deprenylase of i6A RNA

RNA modifications play crucial roles in regulating gene expression and cellular homeostasis. Modulating RNA modifications, particularly by targeting the enzymes responsible for their catalysis, has emerged as a promising therapeutic strategy. However, limitations, such as the lack of identified modifying enzymes and compensatory mechanisms, hinder targeted interventions. Chemical approaches independent of enzymatic activity offer an alternative strategy for RNA modification modulation. Here, we present the identification of 2-chloro-3,5-dinitrobenzoic acid as a highly effective photochemical deprenylase of i6A RNA. This method demonstrates exceptional selectivity towards i6A, converting its substituent into a "N-doped" ozonide, which upon hydrolysis releases natural adenine. We believe that this chemical approach will pave the way for a better understanding of RNA modification biology and the development of novel therapeutic modalities.

TRMT10A dysfunction perturbs codon translation of initiator methionine and glutamine and impairs brain functions in mice

In higher eukaryotes, tRNA methyltransferase 10A (TRMT10A) is responsible for N1-methylguanosine modification at position nine of various cytoplasmic tRNAs. Pathogenic mutations in TRMT10A cause intellectual disability, microcephaly, diabetes, and short stature in humans, and generate cytotoxic tRNA fragments in cultured cells; however, it is not clear how TRMT10A supports codon translation or brain functions. Here, we generated Trmt10a null mice and showed that tRNAGln(CUG) and initiator methionine tRNA levels were universally decreased in various tissues; the same was true in a human cell line lacking TRMT10A. Ribosome profiling of mouse brain revealed that dysfunction of TRMT10A causes ribosome slowdown at the Gln(CAG) codon and increases translation of Atf4 due to higher frequency of leaky scanning of its upstream open reading frames. Broadly speaking, translation of a subset of mRNAs, especially those for neuronal structures, is perturbed in the mutant brain. Despite not showing discernable defects in the pancreas, liver, or kidney, Trmt10a null mice showed lower body weight and smaller hippocampal postsynaptic densities, which is associated with defective synaptic plasticity and memory. Taken together, our study provides mechanistic insight into the roles of TRMT10A in the brain, and exemplifies the importance of universal tRNA modification during translation of specific codons.

Cytokinins Reduce Viral Replication and Alter Plaque Morphology of Frog Virus 3 In Vitro

Cytokinins (CKs) are a group of N6-substituted signaling molecules whose biosynthesis and metabolism have been documented in all kingdoms of life, including vertebrates. While their biological relevance in vertebrate systems continues to be elucidated, they have broadly been documented with therapeutic effects in exogenous applications. In this study, we evaluated the virostatic potential of four types of CKs including, N6-isopentenyladenine (iP), N6-isopentenyladenosine (iPR), N6-isopentenyladenosine-5'monophosphate (iPMP), and 2-methylthiol-N6-isopentenyladenosine (2MeSiPR) against the ranavirus type species, frog virus 3 (FV3). Following concurrent treatment and infection, iP and iPR reduced viral replication by 33.8% and 59.6%, respectively, in plaque formation assays. A decrease in viral replication was also observed when CK exposure was limited to 12 h prior to infection, where iP and iPR reduced viral replication by 31% and 23.75%, respectively. Treatment with iP and iPR was also marked by 48% and 60% decreases in viral load over 72 h, respectively, as measured in single step growth curves. Plaque morphology was altered in vitro, as iP and iPR treatment increased plaque area by 83% and 112% with lytic zone formation also becoming more prevalent in corresponding treatments. Treatment with iPMP and 2MeSiPR resulted in no effect on viral kinetics in vitro. The results of this study are the first to provide evidence of CK antiviral activity against a DNA virus and highlight the importance of their structure for therapeutic investigations.

Targeted i6A-RNA degradation through sequential Fluorination-Azidation and Click reaction with imidazole-based probes

We report the use of trimethylsilyl azide and Selectfluor to implement a standard protocol targeted at the prenylated nucleic acid known as i6A-RNA. After optimizing the conditions, we applied this method to regulate a wide range of i6A-RNA species using synthetic imidazole-based probes (I-IV). We observed that prenylated nucleic acid plays a crucial role in the cell hemostasis in A549 cell lines.

Exploring urinary modified nucleosides as biomarkers for diabetic retinopathy: Development and validation of a ultra performance liquid chromatography-tandem mass spectrometry method

The dynamic modification of RNA plays a crucial role in biological regulation and is strongly linked to human disease development and progression. Notably, modified nucleosides in urine have shown promising potential as early diagnostic biomarkers for various conditions. In this study, we developed and validated a rapid, sensitive, and accurate UPLC-MS/MS method for quantifying eight types of modified nucleosides (N1-methyladenosine (m1A), N6-methyladenosine (m6A), 5-methyluridine (m5U), 5-taurinomethyl-2-thiouridine (τm5s2U), 5-methylcytidine (m5C), 2'-O-methylcytidine (Cm), N1-methylguanosine (m1G), and N7-methylguanosine (m7G) in human urine. Using the method, we measured the urinary concentrations of m1A, m6A, m5U, τm5s2U, m5C, Cm, m1G, and m7G in a total of 21 control individuals and 23 patients diagnosed with diabetic retinopathy (DR). Cm levels showed promise as a diagnostic marker for diabetic retinopathy (DR), with a significant value (P < 0.01) and an AUC of 0.735. Other modified nucleosides also exhibited significant differences within specific subpopulations. As non-proliferative diabetic retinopathy (NPDR) signifies the latent early stage of diabetic retinopathy, we developed a multivariate linear model that integrates patients' sex, age, height, and urinary concentration of modified nucleosides which aims to predict and differentiate between healthy individuals, NPDR patients, and proliferative diabetic retinopathy (PDR) patients. Encouragingly, the model achieved satisfactory accuracy rates: healthy (81%), NPDR (75%), and PDR (80%). Our findings provide valuable insights into the development of an early, cost-effective, and noninvasive diagnostic approach for diabetic retinopathy.

A Preliminary Survey of Transfer RNA Modifications and Modifying Enzymes of the Tropical Plant Cocos nucifera L

The coconut (Cocos nucifera L.) is a commercial crop widely distributed among coastal tropical regions. It provides millions of farmers with food, fuel, cosmetics, folk medicine, and building materials. Among these, oil and palm sugar are representative extracts. However, this unique living species of Cocos has only been preliminarily studied at molecular levels. Benefiting from the genomic sequence data published in 2017 and 2021, we investigated the transfer RNA (tRNA) modifications and modifying enzymes of the coconut in this survey. An extraction method for the tRNA pool from coconut flesh was built. In total, 33 species of modified nucleosides and 66 homologous genes of modifying enzymes were confirmed using a nucleoside analysis using high-performance liquid chromatography combined with high-resolution mass spectrometry (HPLC-HRMS) and homologous protein sequence alignment. The positions of tRNA modifications, including pseudouridines, were preliminarily mapped using a oligonucleotide analysis, and the features of their modifying enzymes were summarized. Interestingly, we found that the gene encoding the modifying enzyme of 2'-O-ribosyladenosine at the 64th position of tRNA (Ar(p)64) was uniquely overexpressed under high-salinity stress. In contrast, most other tRNA-modifying enzymes were downregulated with mining transcriptomic sequencing data. According to previous physiological studies of Ar(p)64, the coconut appears to enhance the quality control of the translation process when subjected to high-salinity stress. We hope this survey can help advance research on tRNA modification and scientific studies of the coconut, as well as thinking of the safety and nutritional value of naturally modified nucleosides.