Parida, A. S. | bioRxiv Science

bioRxiv2024

p53 restores the silencing of activated L1 Transposons

Long Interspersed Nuclear Element 1 (LINE1/L1) retrotransposons, comprising around 17% of the human genome, typically remain quiescent in healthy somatic cells but become activated in various cancer types. Our recent investigation reveals that p53 silences L1 transposons in human somatic cells, potentially constituting a tumor suppressive pathway. In this study, we demonstrate that p53 silences both L1mRNA-gDNA (cis L1 R-loops) and L1mRNA-cDNA hybrids (trans L1 R-loops) formed during retrotransposition. The activation of L1 transposons by HDAC inhibitors (HDACi) led to accumulation of these cis and trans L1 R-loops in p53-/- cells, which were mitigated by treatment with a reverse transcriptase inhibitor. Furthermore, p53 established re-silencing of hyperactivated L1 transposons induced by HDACi. The p53-mediated restoration of silencing was accompanied by recruiting histone repressive marks specifically H3K9me3 and H3K27me3 and inhibiting the deposition of H3K4me3 and H3K9ac marks at the L1 promoter. This study elucidates a novel role of p53 in regulating the formation of RNA-DNA hybrids, a pivotal intermediate component of retrotransposition, and initiating the suppression of hyperactivated L1 elements. These findings underscore the significance of p53 in preserving genome stability through the regulation of L1-derived R-loops. In BriefThe role of L1 transposon derived L1mRNA-cDNA hybrids; an intermediate product formed during retrotransposition, in DNA damage and inflammation is not clear. Paul et al. reveals that p53 prevents L1cDNA derived RNA-DNA hybrids to control DNA damage and activation of inflammatory genes. The findings also elucidate the role of p53 in initiating the repression of hyperactivated transposons by facilitating the recruitment of epigenetic repressive marks and preventing the deposition of activating marks at L1-5UTR. HighlightsO_LIp53 loss facilitates accumulation of both cis (L1mRNA-gDNA) and trans (L1mRNA-cDNA) forms of L1 R-loops. C_LIO_LIThe youngest, actively retrotransposing full-length L1s contribute to the formation of trans (L1mRNA-cDNA) R-loops. C_LIO_LIp53 aids immediate L1 re-silencing by restoring deposition of epigenetic repressive and inhibition of activating marks. C_LIO_LIReverse transcriptase inhibitor prevents L1 mediated DNA damage. C_LI Subject Categories: L1/LINE1, p53, Retrotransposons, RNA-DNA hybrids, Cis R loops, Trans R-loop, L1/LINE1 Graphical O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=123 SRC="FIGDIR/small/589154v3_ufig1.gif" ALT="Figure 1"> View larger version (37K): org.highwire.dtl.DTLVardef@1e37111org.highwire.dtl.DTLVardef@11430c8org.highwire.dtl.DTLVardef@8e9c0corg.highwire.dtl.DTLVardef@a6e98d_HPS_FORMAT_FIGEXP M_FIG C_FIG

cancer biology↗

bioRxiv2023

miRVim: Three-dimensional miRNA Structure Data Server

MicroRNAs (miRNAs), a distinct category of non-coding RNAs, exert multifaceted regulatory functions in a variety of organisms, including humans, animals, and plants. The inventory of identified miRNAs stands at approximately 60,000 among all species and 1,926 in Homo sapiens manifests miRNA expression. Their theranostic role has been explored by researchers over the last few decades, positioning them as prominent therapeutic targets as our understanding of RNA targeting advances. However, the limited availability of experimentally determined miRNA structures has constrained drug discovery efforts relying on virtual screening or computational methods, including machine learning. To address this limitation, miRVim has been developed, providing a repository of human miRNA structures derived from both two-dimensional (MXFold2, CentroidFold, and RNAFold) and three-dimensional (RNAComposer and 3dRNA) structure prediction algorithms, in addition to experimentally available structures from the RCSB PDB repository. This data server aims to facilitate computational data analysis for drug discovery, opening new avenues for advancing technologies such as machine learning-based predictions in the field. The publicly accessible structures provided by miRVim, available at https://mirna.in/miRVim, offer a valuable resource for the research community, advancing the field of miRNA-related computational analysis and drug discovery.

bioinformatics↗