Precise control of microRNA (miRNA) expression is critical during development. An important mechanism of miRNA regulation is target-directed microRNA degradation (TDMD), a pathway in which the binding of miRNAs to specialized trigger RNAs induces ubiquitylation and decay of associated Argonaute (AGO) proteins by the ZSWIM8 ubiquitin ligase. Concomitant release of miRNAs results in their rapid turnover.
View Article and Find Full Text PDFCellular senescence is an irreversible state of cell-cycle arrest induced by various stresses, including aberrant oncogene activation, telomere shortening, and DNA damage. Through a genome-wide screen, we discovered a conserved small nucleolar RNA (snoRNA), SNORA13, that is required for multiple forms of senescence in human cells and mice. Although SNORA13 guides the pseudouridylation of a conserved nucleotide in the ribosomal decoding center, loss of this snoRNA minimally impacts translation.
View Article and Find Full Text PDFCDK4/6 inhibitors (CDK4/6i) have improved survival of patients with estrogen receptor-positive (ER+) breast cancer. However, patients treated with CDK4/6i eventually develop drug resistance and progress. RB1 loss-of-function alterations confer resistance to CDK4/6i, but the optimal therapy for these patients is unclear.
View Article and Find Full Text PDFIncreased nucleolar size and activity correlate with aberrant ribosome biogenesis and enhanced translation in cancer cells. One of the first and rate-limiting steps in translation is the interaction of the 40S small ribosome subunit with mRNAs. Here, we report the identification of the zinc finger protein 692 (ZNF692), a MYC-induced nucleolar scaffold that coordinates the final steps in the biogenesis of the small ribosome subunit.
View Article and Find Full Text PDFCDK4/6 inhibitors (CDK4/6i) have improved survival of patients with estrogen receptor-positive (ER+) breast cancer. However, patients treated with CDK4/6i eventually develop drug resistance and progress. loss-of-function alterations confer acquired resistance to CDK4/6i, but the optimal therapy for these patients is unclear.
View Article and Find Full Text PDFDuring translation of the genomic RNA of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), the causative virus in the COVID-19 pandemic, host ribosomes undergo programmed ribosomal frameshifting (PRF) at a conserved structural element. Although PRF is essential for coronavirus replication, host factors that regulate this process have not yet been identified. Here we perform genome-wide CRISPR-Cas9 knockout screens to identify regulators of SARS-CoV-2 PRF.
View Article and Find Full Text PDFAlthough splicing is a major driver of RNA nuclear export, many intronless RNAs are efficiently exported to the cytoplasm through poorly characterized mechanisms. For example, GC-rich sequences promote nuclear export in a splicing-independent manner, but how GC content is recognized and coupled to nuclear export is unknown. Here, we developed a genome-wide screening strategy to investigate the mechanism of export of , an intronless cytoplasmic long noncoding RNA (lncRNA).
View Article and Find Full Text PDFA Retraction to this paper has been published and can be accessed via a link at the top of the paper.
View Article and Find Full Text PDFSequences within 5' UTRs dictate the site and efficiency of translation initiation. In this study, an unbiased screen designed to interrogate the 5' UTR-mediated regulation of the growth-promoting gene MYC unexpectedly revealed the ribosomal pause relief factor eIF5A as a regulator of translation initiation codon selection. Depletion of eIF5A enhances upstream translation within 5' UTRs across yeast and human transcriptomes, including on the MYC transcript, where this results in increased production of an N-terminally extended protein.
View Article and Find Full Text PDFis a conserved long noncoding RNA (lncRNA) that is required for genome stability in mammals. acts as a negative regulator of PUMILIO (PUM) proteins in the cytoplasm, and we previously showed that loss of or PUM hyperactivity results in genome instability and premature aging in mice (Kopp et al., 2019).
View Article and Find Full Text PDFChange history: In this Letter, the citation to 'Fig. 4e, f' in the main text should be 'Fig. 3e, f'.
View Article and Find Full Text PDFMicroRNAs (miRNAs) are processed from primary miRNA transcripts (pri-miRNAs), many of which are annotated as long noncoding RNAs (lncRNAs). We assessed whether MIR205HG, the host gene for miR-205, has independent functions as an lncRNA. Comparing mice with targeted deletions of MIR205HG and miR-205 revealed a functional role for the lncRNA in the anterior pituitary.
View Article and Find Full Text PDFProper control of microRNA (miRNA) expression is critical for normal development and physiology, while abnormal miRNA expression is a common feature of many diseases. Dissecting mechanisms of miRNA regulation, however, is complicated by the generally poor annotation of miRNA primary transcripts (pri-miRNAs). Although some miRNAs are processed from well-defined protein coding genes, the majority of pri-miRNAs are poorly characterized noncoding RNAs, with incomplete annotation of promoters, splice sites, and polyadenylation signals.
View Article and Find Full Text PDFMicroRNAs (miRNAs) perform critical functions in normal physiology and disease by associating with Argonaute proteins and downregulating partially complementary messenger RNAs (mRNAs). Here we use clustered regularly interspaced short palindromic repeats (CRISPR) and CRISPR-associated protein 9 (Cas9) genome-wide loss-of-function screening coupled with a fluorescent reporter of miRNA activity in human cells to identify new regulators of the miRNA pathway. By using iterative rounds of screening, we reveal a novel mechanism whereby target engagement by Argonaute 2 (AGO2) triggers its hierarchical, multi-site phosphorylation by CSNK1A1 on a set of highly conserved residues (S824-S834), followed by rapid dephosphorylation by the ANKRD52-PPP6C phosphatase complex.
View Article and Find Full Text PDFLong noncoding RNAs (lncRNAs) have emerged as regulators of diverse biological processes. Here, we describe the initial functional analysis of a poorly characterized human lncRNA (LINC00657) that is induced after DNA damage, which we termed "noncoding RNA activated by DNA damage", or NORAD. NORAD is highly conserved and abundant, with expression levels of approximately 500-1,000 copies per cell.
View Article and Find Full Text PDFPrecise regulation of microRNA (miRNA) expression is critical for diverse physiologic and pathophysiologic processes. Nevertheless, elucidation of the mechanisms through which miRNA expression is regulated has been greatly hindered by the incomplete annotation of primary miRNA (pri-miRNA) transcripts. While a subset of miRNAs are hosted in protein-coding genes, the majority of pri-miRNAs are transcribed as poorly characterized noncoding RNAs that are 10's to 100's of kilobases in length and low in abundance due to efficient processing by the endoribonuclease DROSHA, which initiates miRNA biogenesis.
View Article and Find Full Text PDFMethods used to sequence the transcriptome often produce more than 200 million short sequences. We introduce StringTie, a computational method that applies a network flow algorithm originally developed in optimization theory, together with optional de novo assembly, to assemble these complex data sets into transcripts. When used to analyze both simulated and real data sets, StringTie produces more complete and accurate reconstructions of genes and better estimates of expression levels, compared with other leading transcript assembly programs including Cufflinks, IsoLasso, Scripture and Traph.
View Article and Find Full Text PDFWilms tumour is the most common childhood kidney cancer. Here we report the whole-exome sequencing of 44 Wilms tumours, identifying missense mutations in the microRNA (miRNA)-processing enzymes DROSHA and DICER1, and novel mutations in MYCN, SMARCA4 and ARID1A. Examination of tumour miRNA expression, in vitro processing assays and genomic editing in human cells demonstrates that DICER1 and DROSHA mutations influence miRNA processing through distinct mechanisms.
View Article and Find Full Text PDFBone-resorbing osteoclasts significantly contribute to osteoporosis and bone metastases of cancer. MicroRNAs play important roles in physiology and disease, and present tremendous therapeutic potential. Nonetheless, how microRNAs regulate skeletal biology is underexplored.
View Article and Find Full Text PDFTherapeutic strategies based on modulation of microRNA (miRNA) activity hold great promise due to the ability of these small RNAs to potently influence cellular behavior. In this study, we investigated the efficacy of a miRNA replacement therapy for liver cancer. We demonstrate that hepatocellular carcinoma (HCC) cells exhibit reduced expression of miR-26a, a miRNA that is normally expressed at high levels in diverse tissues.
View Article and Find Full Text PDFAltered glucose metabolism in cancer cells is termed the Warburg effect, which describes the propensity of most cancer cells to take up glucose avidly and convert it primarily to lactate, despite available oxygen. Notwithstanding the renewed interest in the Warburg effect, cancer cells also depend on continued mitochondrial function for metabolism, specifically glutaminolysis that catabolizes glutamine to generate ATP and lactate. Glutamine, which is highly transported into proliferating cells, is a major source of energy and nitrogen for biosynthesis, and a carbon substrate for anabolic processes in cancer cells, but the regulation of glutamine metabolism is not well understood.
View Article and Find Full Text PDFProc Natl Acad Sci U S A
March 2009
Direct control of microRNA (miRNA) expression by oncogenic and tumor suppressor networks results in frequent dysregulation of miRNAs in cancer cells and contributes to tumorigenesis. We previously demonstrated that activation of the c-Myc oncogenic transcription factor (Myc) broadly influences miRNA expression and in particular leads to widespread miRNA down-regulation. miRNA transcripts repressed by Myc include several with potent tumor suppressor activity such as miR-15a/16-1, miR-34a, and let-7 family members.
View Article and Find Full Text PDFCancer Biol Ther
November 2008
The dleu2 tumor suppressor locus encodes two microRNAs, miR-15a and miR-16, which are thought to play an important role in B-cell neoplasms. However, relatively little is known about proteins that regulate or are regulated by this microRNA cluster. Here we demonstrate that the Pax5 oncoprotein downregulates the dleu2 gene and at the same time boosts expression of its own heterodimeric partner c-Myb.
View Article and Find Full Text PDFThe c-Myc oncogenic transcription factor (Myc) is pathologically activated in many human malignancies. Myc is known to directly upregulate a pro-tumorigenic group of microRNAs (miRNAs) known as the miR-17-92 cluster. Through the analysis of human and mouse models of B cell lymphoma, we show here that Myc regulates a much broader set of miRNAs than previously anticipated.
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