A growing class of small RNAs, known as tRNA-derived RNAs (tdRs), tRNA-derived small RNAs or tRNA-derived fragments, have long been considered mere intermediates of tRNA degradation. These small RNAs have recently been implicated in an evolutionarily conserved repertoire of biological processes. In this Review, we discuss the biogenesis and molecular functions of tdRs in mammals, including tdR-mediated gene regulation in cell metabolism, immune responses, transgenerational inheritance, development and cancer.
View Article and Find Full Text PDFSF3B1 is the most mutated splicing factor (SF) in myelodysplastic syndromes (MDSs), which are clonal hematopoietic disorders with variable risk of leukemic transformation. Although tumorigenic SF3B1 mutations have been extensively characterized, the role of "non-mutated" wild-type SF3B1 in cancer remains largely unresolved. Here, we identify a conserved epitranscriptomic program that steers SF3B1 levels to counteract leukemogenesis.
View Article and Find Full Text PDFMLL-rearrangements (MLL-r) are recurrent genetic events in acute myeloid leukemia (AML) and frequently associate with poor prognosis. In infants, MLL-r can be sufficient to drive transformation. However, despite the prenatal origin of MLL-r in these patients, congenital leukemia is very rare with transformation usually occurring postnatally.
View Article and Find Full Text PDFTransfer RNA-derived fragments (tRFs) are emerging small noncoding RNAs that, although commonly altered in cancer, have poorly defined roles in tumorigenesis. Here we show that pseudouridylation (Ψ) of a stem cell-enriched tRF subtype, mini tRFs containing a 5' terminal oligoguanine (mTOG), selectively inhibits aberrant protein synthesis programmes, thereby promoting engraftment and differentiation of haematopoietic stem and progenitor cells (HSPCs) in patients with myelodysplastic syndrome (MDS). Building on evidence that mTOG-Ψ targets polyadenylate-binding protein cytoplasmic 1 (PABPC1), we employed isotope exchange proteomics to reveal critical interactions between mTOG and functional RNA-recognition motif (RRM) domains of PABPC1.
View Article and Find Full Text PDFWe previously reported that loss of mitochondrial transcription factor B1 (TFB1M) leads to mitochondrial dysfunction and is involved in the pathogenesis of type 2 diabetes (T2D). Whether defects in ribosomal processing impact mitochondrial function and could play a pathogenetic role in β-cells and T2D is not known. To this end, we explored expression and the functional role of dimethyladenosine transferase 1 homolog (DIMT1), a homolog of TFB1M and a ribosomal RNA (rRNA) methyltransferase implicated in the control of rRNA.
View Article and Find Full Text PDFSmall Cajal body-specific RNAs (scaRNAs) guide post-transcriptional modification of spliceosomal RNA and, while commonly altered in cancer, have poorly defined roles in tumorigenesis. Here, we uncover that SCARNA15 directs alternative splicing (AS) and stress adaptation in cancer cells. Specifically, we find that SCARNA15 guides critical pseudouridylation (Ψ) of U2 spliceosomal RNA to fine-tune AS of distinct transcripts enriched for chromatin and transcriptional regulators in malignant cells.
View Article and Find Full Text PDFSplicing is a central RNA-based process commonly altered in human cancers; however, how spliceosomal components are co-opted during tumorigenesis remains poorly defined. Here we unravel the core splice factor SF3A3 at the nexus of a translation-based program that rewires splicing during malignant transformation. Upon MYC hyperactivation, SF3A3 levels are modulated translationally through an RNA stem-loop in an eIF3D-dependent manner.
View Article and Find Full Text PDFProteogenomic identification of translated small open reading frames in humans has revealed thousands of microproteins, or polypeptides of fewer than 100 amino acids, that were previously invisible to geneticists. Hundreds of microproteins have been shown to be essential for cell growth and proliferation, and many regulate macromolecular complexes. One such regulatory microprotein is NBDY, a 68-amino acid component of the human cytoplasmic RNA decapping complex.
View Article and Find Full Text PDFXRN1 is the major cytoplasmic exoribonuclease in eukaryotes, which degrades deadenylated and decapped mRNAs in the last step of the 5'-3' mRNA decay pathway. Metazoan XRN1 interacts with decapping factors coupling the final stages of decay. Here, we reveal a direct interaction between XRN1 and the CCR4-NOT deadenylase complex mediated by a low-complexity region in XRN1, which we term the 'C-terminal interacting region' or CIR.
View Article and Find Full Text PDFCCR4-NOT is a conserved multiprotein complex which regulates eukaryotic gene expression principally via shortening of poly(A) tails of messenger RNA or deadenylation. Here, we reconstitute a complete, recombinant human CCR4-NOT complex. Our reconstitution strategy permits strict compositional control to test mechanistic hypotheses with purified component variants.
View Article and Find Full Text PDFThe removal of the mRNA 5' cap (decapping) by Dcp2 shuts down translation and commits mRNA to full degradation. Dcp2 activity is enhanced by activator proteins such as Dcp1 and Edc1. However, owing to conformational flexibility, the active conformation of Dcp2 and the mechanism of decapping activation have remained unknown.
View Article and Find Full Text PDFProofreading modules of aminoacyl-tRNA synthetases are responsible for enforcing a high fidelity during translation of the genetic code. They use strategically positioned side chains for specifically targeting incorrect aminoacyl-tRNAs. Here, we show that a unique proofreading module possessing a D-aminoacyl-tRNA deacylase fold does not use side chains for imparting specificity or for catalysis, the two hallmark activities of enzymes.
View Article and Find Full Text PDFThe biological macromolecular world is homochiral and effective enforcement and perpetuation of this homochirality is essential for cell survival. In this study, we present the mechanistic basis of a configuration-specific enzyme that selectively removes D-amino acids erroneously coupled to tRNAs. The crystal structure of dimeric D-aminoacyl-tRNA deacylase (DTD) from Plasmodium falciparum in complex with a substrate-mimicking analog shows how it uses an invariant 'cross-subunit' Gly-cisPro dipeptide to capture the chiral centre of incoming D-aminoacyl-tRNA.
View Article and Find Full Text PDFThe beneficial effects of fruits and vegetables with respect to age-related diseases such as diabetes, atherosclerosis and several types of cancer are widely recognized and confirmed by several epidemiological studies. A possible approach for evaluating the protective potential of promising diet constituents is to evaluate their beneficial effect with respect to a set of biomarkers that are indicative of a potential risk for developing degenerative diseases. Among the numerous biomarkers of the effect of food-related carcinogens and for the assessment of the degree of risk for disease, chromosomal damage detection is very predictive.
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