Epigenetic loss of the transfer RNA-modifying enzyme TYW2 induces ribosome frameshifts in colon cancerProc Natl Acad Sci U S A. 2020 Aug 25 1 Ago 2020, 117(34):20785-20793 .
Transfer RNA (tRNA) activity is tightly regulated to provide a physiological protein translation, and tRNA chemical modifications control its function in a complex with ribosomes and messenger RNAs (mRNAs). In this regard, the correct hypermodification of position G37 of phenylalanine-tRNA, adjacent to the anticodon, is critical to prevent ribosome frameshifting events. Here we report that the tRNA-yW Synthesizing Protein 2 (TYW2) undergoes promoter hypermethylation-associated transcriptional silencing in human cancer, particularly in colorectal tumors. The epigenetic loss of TYW2 induces guanosine hypomodification in phenylalanine-tRNA, an increase in -1 ribosome frameshift events, and down-regulation of transcripts by mRNA decay, such as of the key cancer gene ROBO1. Importantly, TYW2 epigenetic inactivation is linked to poor overall survival in patients with early-stage colorectal cancer, a finding that could be related to the observed acquisition of enhanced migration properties and epithelial-to-mesenchymal features in the colon cancer cells that harbor TYW2 DNA methylation-associated loss. These findings provide an illustrative example of how epigenetic changes can modify the epitranscriptome and further support a role for tRNA modifications in cancer biologyMás información
SirT7 auto-ADP-ribosylation regulates glucose starvation response through mH2A1Science Advances 24 Jul 2020, 6 .
Sirtuins are key players of metabolic stress response. Originally described as deacetylases, some sirtuins also exhibit poorly understood mono–adenosine 5′-diphosphate (ADP)–ribosyltransferase (mADPRT) activity. We report that the deacetylase SirT7 is a dual sirtuin, as it also features auto-mADPRT activity. SirT7 mADPRT occurs at a previously undefined active site, and its abrogation alters SirT7 chromatin distribution. We identify an epigenetic pathway by which ADP-ribosyl-SirT7 is recognized by the ADP-ribose reader mH2A1.1 under glucose starvation, inducing SirT7 relocalization to intergenic regions. SirT7 promotes mH2A1 enrichment in a subset of nearby genes, many of them involved in second messenger signaling, resulting in their specific up- or down-regulation. The expression profile of these genes under calorie restriction is consistently abrogated in SirT7-deficient mice, resulting in impaired activation of autophagy. Our work provides a novel perspective on sirtuin duality and suggests a role for SirT7/mH2A1.1 axis in glucose homeostasis and aging.
The Contribution of Epigenetics to Cancer ImmunotherapyTrends in Immunology 1 Jul 2020, .
Effective anticancer immunotherapy treatments constitute a qualitative leap in cancer management. Nonetheless, not all patients benefit from such therapies because they fail to achieve complete responses, suffer frequent relapses, or develop potentially life-threatening toxicities. Epigenomic signatures in immune and cancer cells appear to be accurate and promising predictors of patient outcomes with immunotherapy. In addition, combined treatments with epigenetic drugs can exploit the dynamic nature of epigenetic changes to potentially modulate responses to immunotherapy. Candidate epigenetic biomarkers may provide a rationale for patient stratification and precision medicine, thus maximizing the chances of treatment success while minimizing unwanted effects. We present a comprehensive up-to-date view of potential epigenetic biomarkers in immunotherapy and discuss their advantages over other indicators.Más información
Epitranscriptomics in Hematopoiesis and Hematologic Malignancies.Blood Cancer Discovery 22 Jun 2020, .
Since the 1960s, a large number of chemical modifications have been identified in RNA molecules, establishing the RNA epigenetics field named “epitranscriptomics.” These chemical marks participate in several RNA metabolic processes; however, the biological relevance of many of these modifications and the many enzymes involved in their function is not completely understood. Emerging knowledge of the epitranscriptome (pseudouridine, N6-methyladenosine, and A-to-I editing) in hematopoiesis and hematologic malignancies reveals the requirement of these modifications in normal development and their alteration in disorders, leading to the development of new molecules and strategies to target the epitranscriptome as a novel therapeutic approach. RNA modifications are required for the correct development of hematopoietic cells, and their alteration can promote the development of malignancies or the transition from a low-grade to an aggressive disease. While we are expanding our understanding of the epitranscriptome of normal and malignant hematopoiesis, the number of potential new therapeutic interventions is rising.