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Medhi, R.

Publications and source records attributed to Medhi, R..

2 recordsLinked to original sources
bioRxiv2021

RNA uridyl transferases TUT4/7 differentially regulate miRNA variants depending on the cancer cell-type

The human terminal uridyl transferases TUT4 and TUT7 (TUT4/7) catalyse additions of uridines at the 3' end of RNAs such as the precursors of the tumour suppressor miRNA let-7, upon recruitment by the oncoprotein LIN28A. Consequently, let-7 family miRNAs are downregulated. Disruption of this TUT4/7 activity inhibits tumorigenesis and hence targeting TUT4/7 can be a potential anti-cancer therapy. In this study, we investigate TUT4/7-mediated RNA regulation in two cancer cell lines by establishing catalytic knockout models. Upon TUT4/7 mutation, we observe a significant reduction in miRNA uridylation, which results in defects in cancer cell properties such as cell proliferation and migration. With the loss of TUT4/7-mediated miRNA uridylation, the uridylated miRNA variants are replaced by adenylated isomiRs. Changes in miRNA modification profiles are accompanied by deregulation of expression levels in specific cases. Unlike let-7s, most miRNAs do not depend on LIN28A for TUT4/7-mediated regulation. Additionally, we identify TUT4/7-regulated cell-type-specific miRNA clusters and deregulation in their corresponding mRNA targets. Expression levels of miR-200c-3p and miR-141-3p are regulated by TUT4/7 in a cancer cell type specific manner. Subsequently, BCL2 which is a well-established target of miR-200c is upregulated. Therefore, TUT4/7 loss triggers deregulation of miRNA-mRNA networks in a cell-type-specific manner. Understanding of the underlying biology of such cell-type-specific deregulation will be key when targeting TUT4/7 for cancer therapy. Graphical Abstract O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=198 SRC="FIGDIR/small/451846v2_ufig1.gif" ALT="Figure 1"> View larger version (53K): org.highwire.dtl.DTLVardef@a18bdcorg.highwire.dtl.DTLVardef@1e5534forg.highwire.dtl.DTLVardef@c08e76org.highwire.dtl.DTLVardef@1c90423_HPS_FORMAT_FIGEXP M_FIG C_FIG Highlights TUT4/7 catalyse 3' uridylation of most miRNAs Loss of uridylated isomiRs leads to the gain of adenylated isomiRs TUT4/7-mediated miRNA deregulation and miRNA-mRNA interactions are specific to the cell line type Loss of TUT4/7-mediated RNA uridylation inhibits cancer cell function

molecular biology↗
bioRxiv2016

The Aquarius/EMB-4 helicase licenses co-transcriptional gene silencing

Small RNAs (sRNAs) play an ancient role in genome defence against transposable elements. In animals, plants and fungi small RNAs guide Argonaute proteins to nascent RNA transcripts to induce co-transcriptional gene silencing. In animals the link between small RNA pathways and the transcriptional machinery remains unclear. Here we show that the Caenorhabditis elegans germline Argonaute HRDE-1 physically interacts with the conserved RNA helicase Aquarius/EMB-4. We demonstrate that the Aquarius/EMB-4 helicase activity is required to initiate small RNA-induced co-transcriptional gene silencing. HRDE-1 and Aquarius/EMB-4 are required to silence the transcription of overlapping sets of transposable elements. Surprisingly, removal of introns from a small RNA pathway target abolishes the requirement for Aquarius/EMB-4, but not HRDE-1, for gene silencing. We conclude that the Aquarius/EMB-4 helicase activity allows HRDE-1/sRNA complexes to efficiently engage nascent RNA transcripts - in competition with the general RNA processing machinery. We postulate that Aquarius/EMB-4 facilitates the surveillance of the nascent transcriptome to detect and silence transposable elements through small RNA pathways.

molecular biology↗