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Absolute quantitative and base-resolution sequencing reveals comprehensive landscape of pseudouridine across the human transcriptome
AbstractPseudouridine (Ψ) is one of the most abundant modifications in cellular RNA. However, its function remains elusive, mainly due to the lack of highly sensitive and accurate detection methods. Here, we introduced 2-bromoacrylamide-assisted cyclization sequencing (BACS), which enables Ψ-to-C transitions, for quantitative profiling of Ψ at single-base resolution. BACS allowed the precise identification of Ψ positions, especially in densely modified Ψ regions and consecutive uridine sequences. BACS detected all known Ψ sites in human rRNA and spliceosomal small nuclear RNAs and generated the quantitative Ψ map of human small nucleolar RNA and tRNA. Furthermore, BACS simultaneously detected adenosine-to-inosine editing sites and N1-methyladenosine. Depletion of pseudouridine synthases TRUB1, PUS7 and PUS1 elucidated their targets and sequence motifs. We further identified a highly abundant Ψ114 site in Epstein–Barr virus-encoded small RNA EBER2. Surprisingly, applying BACS to a panel of RNA viruses demonstrated the absence of Ψ in their viral transcripts or genomes, shedding light on differences in pseudouridylation across virus families.
Data from GTP cyclohydrolase drives breast cancer development and promotes EMT in an enzyme-independent manner
<div>Abstract<p>GTP cyclohydrolase (GCH1) is the rate-limiting enzyme for tetrahydrobiopterin (BH4) biosynthesis. The catalysis of BH4 biosynthesis is tightly regulated for physiological neurotransmission, inflammation, and vascular tone. Paradoxically, BH4 has emerged as an oncometabolite regulating tumor growth, but the effects on tumor development remain controversial. Here we found that GCH1 potentiates the growth of triple-negative breast cancer (TNBC) and HER2+ breast cancer and transforms non-tumor breast epithelial cells. Independent of BH4 production, GCH1 protein induced epithelial-to-mesenchymal transition IEMT) by binding to Vim, which was mediated by HSP90. Conversely, GCH1 ablation impaired tumor growth, suppressed Vim in TNBC, and inhibited EGFR/ERK signaling while activating the p53 pathway in estrogen receptor-positive tumor cells. GCH1 deficiency increases tumor cell sensitivity to HSP90 inhibition and endocrine treatments. Additionally, high GCH1 corelated with poor breast cancer survival. Together, this study reveals an enzyme-independent oncogenic role of GCH1, presenting it as a potential target for therapeutic development.</p></div>
Supplementary Data from GTP cyclohydrolase drives breast cancer development and promotes EMT in an enzyme-independent manner
<p>Tables and figure legends</p>
Supplementary Figures from GTP cyclohydrolase drives breast cancer development and promotes EMT in an enzyme-independent manner
<p>Supplementary Figures S1-S11</p>
Supplementary Figures from GTP cyclohydrolase drives breast cancer development and promotes EMT in an enzyme-independent manner
<p>Supplementary Figures S1-S11</p>
Supplementary Data from GTP cyclohydrolase drives breast cancer development and promotes EMT in an enzyme-independent manner
<p>Tables and figure legends</p>
Differential roles for the oxygen sensing enzymes PHD1 and PHD3 in the regulation of neutrophil metabolism and function.
Neutrophils are essential in the early innate immune response to pathogens. Harnessing their antimicrobial powers, without driving excessive and damaging inflammatory responses, represents an attractive therapeutic possibility. The neutrophil population is increasingly recognised to be more diverse and malleable than was previously appreciated. Hypoxic signalling pathways are known to regulate important neutrophil behaviours and, as such, are potential therapeutic targets for regulating neutrophil antimicrobial and inflammatory responses. We used a combination of in vivo and ex vivo models, utilising neutrophil and myeloid specific PHD1 or PHD3 deficient mouse lines to investigate the roles of oxygen sensing prolyl hydroxylase enzymes in the regulation of neutrophilic inflammation and immunity. Mass spectrometry and Seahorse metabolic flux assays were used to analyse the role of metabolic shifts in driving the downstream phenotypes. We found that PHD1 deficiency drives alterations in neutrophil metabolism and recruitment, in an oxygen dependent fashion. Despite this, PHD1 deficiency did not significantly alter ex vivo neutrophil phenotypes or in vivo outcomes in mouse models of inflammation. Conversely, PHD3 deficiency was found to enhance neutrophil antibacterial properties without excessive inflammatory responses. This was not linked to changes in the abundance of core metabolites but was associated with increased oxygen consumption and increased mitochondrial reactive oxygen species (mROS) production. PHD3 deficiency drives a favourable neutrophil phenotype in infection and, as such, is an important potential therapeutic target.
Ubiquitylation of nucleic acids by DELTEX ubiquitin E3 ligase DTX3L
AbstractThe recent discovery of non-proteinaceous ubiquitylation substrates broadened our understanding of this modification beyond conventional protein targets. However, the existence of additional types of substrates remains elusive. Here, we present evidence that nucleic acids can also be directly ubiquitylated via ester bond formation. DTX3L, a member of the DELTEX family E3 ubiquitin ligases, ubiquitylates DNA and RNA in vitro and that this activity is shared with DTX3, but not with the other DELTEX family members DTX1, DTX2 and DTX4. DTX3L shows preference for the 3′-terminal adenosine over other nucleotides. In addition, we demonstrate that ubiquitylation of nucleic acids is reversible by DUBs such as USP2, JOSD1 and SARS-CoV-2 PLpro. Overall, our study proposes reversible ubiquitylation of nucleic acids in vitro and discusses its potential functional implications.
Direct, Quantitative, and Base-Resolution Sequencing of DNA and RNA Modifications
Cellular DNA and RNA are decorated with diverse chemical modifications, which add new layers to gene regulation and play crucial roles across development and disease progression. Interest in understanding the functions of DNA and RNA modifications, as well as the related molecular mechanisms, has been growing, driving progress in developing chemical and biochemical tools to detect specific modifications. New technologies are important not only for uncovering biological functions, but also for driving conceptual revolutions. In this review, we highlighted our recent advances in developing new chemical tools to detect DNA and RNA modifications in a direct, quantitative, and base-resolution manner. These includes a novel borane reduction chemistry for DNA methylation sequencing; new cytosine modificaiton oxdation chemistry for enhanced DNA hydroxymethylation sequencing; and a novel bromoacrylamide cyclization chemistry for RNA pseudouridylation sequencing. We present a mechanistic overview of these tools and their applications in epigenetic and epitranscriptomic research.
The N6-methyladenosine demethylase ALKBH5 regulates the hypoxic HBV transcriptome.
Chronic hepatitis B is a global health problem and current treatments only suppress hepatitis B virus (HBV) infection, highlighting the need for new curative treatments. Oxygen levels influence HBV replication and we previously reported that hypoxia inducible factors (HIFs) activate the basal core promoter (BCP). Here we show that the hypoxic-dependent increase in BCP-derived transcripts is dependent on N6-methyladenosine (m6A) modifications in the 5' stem loop that regulate RNA half-life. Application of a probe-enriched long-read sequencing method to accurately map the HBV transcriptome showed an increased abundance of pre-genomic RNA under hypoxic conditions. Mapping the transcription start sites of BCP-RNAs identified a role for hypoxia to regulate pre-genomic RNA splicing that is dependent on m6A modification. Bioinformatic analysis of published single cell RNA-seq of murine liver showed an increased expression of the RNA demethylase ALKBH5 in the peri-central low oxygen region. In vitro studies with a human hepatocyte derived HepG2-NTCP cell line showed increased ALKBH5 gene expression under hypoxic conditions and a concomitant reduction in m6A-modified HBV BCP-RNA and host RNAs. Silencing the demethylase reduced the level of BCP-RNAs and host gene (CA9, NDRG1, VEGFA, BNIP3, FUT11, GAP and P4HA1) transcripts and this was mediated via reduced HIFα expression. In summary, our study highlights a previously unrecognized role for ALKBH5 in orchestrating viral and cellular transcriptional responses to low oxygen.