Implications of widespread covalent modification of mRNA

Deciphering the pseudouridine nucleobase modification in human diseases: From molecular mechanisms to clinical perspectives

RNA pseudouridylation, a dynamic and reversible post-transcriptional modification found in diverse RNA species, is crucial for various biological processes, including tRNA homeostasis, tRNA transport, translation initiation regulation, pre-mRNA splicing, enhancement of mRNA translation, and translational fidelity. Disruption of pseudouridylation impairs cellular homeostasis, contributing to pathological alterations. Recent studies have highlighted its regulatory role in human diseases, particularly in tumourigenesis. Cellular stresses trigger RNA pseudouridylation in organisms, suggesting that pseudouridylation-mediated epigenetic reprogramming is essential for maintaining cellular viability and responding to stress. This review examines the regulatory mechanisms and pathological implications of pseudouridylation in human diseases, with a focus on its involvement in tumourigenesis. Additionally, it explores the therapeutic potential of targeting pseudouridylation, presenting novel strategies for disease treatment. HIGHLIGHTS: Methods to detect pseudouridine were introduced from classic mass spectrometry-based methods to newer approaches such as nanopore-based technologies and BID sequencing, each with its advantages and limitations. RNA pseudouridylation is crucial for various biological processes, including tRNA homeostasis, tRNA transport, translation initiation regulation, pre-mRNA splicing, enhancement of mRNA translation, and translational fidelity. Increased pseudouridylation is frequently associated with tumour initiation, progression, and poor prognosis, whereas its reduction is predominantly implicated in non-tumour diseases. A comprehensive understanding of the inducing factors for RNA pseudouridylation will be essential for elucidating its role in diseases. Such insights can provide robust evidence for how pseudouridylation influences disease progression and offer new avenues for therapeutic strategies targeting pseudouridylation dysregulation. The therapeutic potential of RNA pseudouridylation in diseases is enormous, including inhibitors targeting pseudouridine synthases, the application of RNA pseudouridylation in RNA therapeutics, and its role as a biological marker.

Multilevel regulation of N6-methyladenosine RNA modifications: Implications in tumorigenesis and therapeutic opportunities

N⁶-methyladenosine (m⁶A) RNA modification is widely perceived as the most abundant and common modification in transcripts. This modification is dynamically regulated by specific m⁶A "writers", "erasers" and "readers" and is reportedly involved in the occurrence and development of many diseases. Since m⁶A RNA modification was discovered in the 1970s, with the progress of relevant research technologies, an increasing number of functions of m⁶A have been reported, and a preliminary understanding of m⁶A has been obtained. In this review, we summarize the mechanisms through which m⁶A RNA modification is regulated from the perspectives of expression, posttranslational modification and protein interaction. In addition, we also summarize how external and internal environmental factors affect m⁶A RNA modification and its functions in tumors. The mechanisms through which m⁶A methylases, m⁶A demethylases and m⁶A-binding proteins are regulated are complicated and have not been fully elucidated. Therefore, we hope to promote further research in this field by summarizing these mechanisms and look forward to the future application of m⁶A in tumors.

Multi-Omics Analysis Reveals the Dynamic Changes of RNA N 6 -Methyladenosine in Pear (Pyrus bretschneideri) Defense Responses to Erwinia amylovora Pathogen Infection

N6-methylated adenine (m⁶A) is the most prevalent modification of mRNA methylation and can regulate many biological processes in plants, such as mRNA processing, development, and stress response. Some studies have increased our understanding of its various roles in model plants in recent years. Nevertheless, the distribution of m⁶A and the impact of m⁶A on the regulation of plant defense responses against pathogen inoculation are virtually unknown in pear. In this study, MeRIP-seq and RNA-seq data from healthy and inoculated plants were analyzed to assess the changes in the transcript levels and posttranscriptional modification of pear in response to the fire blight pathogen Erwinia amylovora. Following the analysis of 97,261 m⁶A peaks, we found that m⁶A preferred to modify duplicate genes rather than singleton genes and that m⁶A-methylated genes underwent stronger purifying selection. A total of 2,935 specific m⁶A sites were detected at the transcriptome level after inoculation, which may increase defense-related transcript abundance to enhance pear resistance. In addition, 1,850 transcripts were detected only in the mock-inoculated groups. The hypomethylated transcripts were mainly related to transcriptional regulation and various biological processes, such as chloroplast organization and sucrose biosynthetic processes. In addition, we found that the extent of m⁶A methylation was significantly positively correlated with the transcript level, suggesting a regulatory role for m⁶A in the plant response.

N6-Methyladenine hinders RNA- and DNA-directed DNA synthesis: application in human rRNA methylation analysis of clinical specimens

N⁶-Methyladenine (m⁶A) is the most abundant internal modification on mammalian mRNA. Very recently, m⁶A has been reported as a potentially important 'epigenetic' mark in eukaryotes. Until now, site-specific detection of m⁶A is technically very challenging. Here, we first reveal that m⁶A significantly hinders DNA- and RNA-directed DNA synthesis. Systematic investigations of 5'-triphosphates of a variety of 5-substituted 2'-deoxyuridine analogs in primer extension have been performed. In the current study, a quantitative analysis of m⁶A in the RNA or DNA context has been achieved, using Bst DNA polymerase catalyzed primer extension. Molecular dynamics study predicted that m⁶A in template tends to enter into and be restrained in the MGR region of Bst DNA polymerase, reducing conformational flexibility of the DNA backbone. More importantly, a site-specific determination of m⁶A in human ribosomal RNA (rRNA) with high accuracy has been afforded. Through a cumulative analysis of methylation alterations, we first reveal that significantly cancer-related changes in human rRNA methylation were present in patients with hepatocellular carcinoma.