Hastert, F. D. | bioRxiv Science

bioRxiv2025

TET dioxygenases localize at splicing speckles and promote RNA splicing

The dynamic regulation of RNA metabolism plays a crucial part in cellular function, with emerging evidence suggesting an important role for RNA modifications in this process. This study explores the relationship between RNA splicing and the TET dioxygenase activity, shedding light on the role of hm5C (RNA 5-hydroxymethylcytosine), and TET proteins, in RNA metabolism. Integrating data from mass spectrometry, AlphaFold structural modeling, microscopic analysis, and different functional assays including in vitro splicing, TET proteins were found to regulate splicing. We show that TET1, TET2, and TET3 interact with the splicing factors U2AF1 and U2AF2. Interestingly, TET dioxygenases localize in splicing speckles in mammalian and Drosophila cells. TET speckles association is RNA dependent, as it is TET interaction with splicing factors. Furthermore, in vitro splicing assays revealed that all three TET proteins promote splicing efficiency, and the oxidation of m5C to hm5C can restore splicing efficiency in vitro. The latter highlights the regulatory role of cytosine modifications in RNA metabolism. These findings provide insights into the complex interplay between RNA modifications and splicing, suggesting a multifaceted role for TET proteins in RNA metabolism beyond its canonical DNA demethylation function. Graphical abstract O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=104 SRC="FIGDIR/small/641893v1_ufig1.gif" ALT="Figure 1"> View larger version (44K): org.highwire.dtl.DTLVardef@1a304bborg.highwire.dtl.DTLVardef@18b91d3org.highwire.dtl.DTLVardef@12efeforg.highwire.dtl.DTLVardef@1464355_HPS_FORMAT_FIGEXP M_FIG C_FIG Highlights- TET1 localizes in splicing speckles in an RNA-dependent manner - TET proteins, especially TET1, interact with the splicing factors U2AF1 and U2AF2 - TET proteins increase splicing efficiency, independent of their catalytic activity - RNA 5-methylcytosine (m5C) oxidation to 5-hydroxymethylcytosine (hm5C) restores splicing efficiently in vitro

cell biology↗

bioRxiv2022

SARS-CoV-2 entry route impacts a range of downstream viral and cellular processes

SARS-CoV-2 entry is promoted by both cell-surface TMPRSS2 and endolysosomal cathepsins. To investigate the impact of differentially routed virions on host and viral processes, lung epithelial cells expressing distinct combinations of entry factors were infected with authentic viruses. Entry route determined early rates of viral replication and transcription, egress and inhibitor sensitivity, with differences observed between virus strains. Transcriptional profiling revealed that induction of innate immunity was correlated to viral genome and transcript abundance in infected cells. Surface entry triggered early activation of antiviral responses, reducing cumulative virion production, while endolysosomal entry delayed antiviral responses and prolonged virus shedding due to extended cell viability. The likely molecular footprints of escape from antiviral effector targeting were also recorded in viral genomes and correlated with entry route-dependent immune status of cells. TMPRSS2 orthologues from diverse mammals, but not zebra fish, facilitated infection enhancement, which was more pronounced for ancestral strains. Leveraging RNA-seq and scRNA-seq datasets from SARS-CoV-2 infected hamsters, we validate aspects of our model in vivo. In summary, we demonstrate that distinct cellular and viral processes are linked to viral entry route, collectively modulating virus shedding, cell-death rates and viral genome evolution.

microbiology↗