miR-15a targets the HSP90 co-chaperone Morgana in chronic myeloid leukemia.

Morgana is a ubiquitous HSP90 co-chaperone protein coded by the CHORDC1 gene. Morgana heterozygous mice develop with age a myeloid malignancy resembling human atypical myeloid leukemia (aCML), now renamed MDS/MPN with neutrophilia. Patients affected by this pathology exhibit low Morgana levels in the bone marrow (BM), suggesting that Morgana downregulation plays a causative role in the human malignancy. A decrease in Morgana expression levels is also evident in the BM of a subgroup of Philadelphia-positive (Ph+) chronic myeloid leukemia (CML) patients showing resistance or an incomplete response to imatinib. Despite the relevance of these data, the mechanism through which Morgana expression is downregulated in patients' bone marrow remains unclear. In this study, we investigated the possibility that Morgana expression is regulated by miRNAs and we demonstrated that Morgana is under the control of four miRNAs (miR-15a/b and miR-26a/b) and that miR-15a may account for Morgana downregulation in CML patients.

A SARS-CoV-2 sequence submission tool for the European Nucleotide Archive.

SUMMARY: Many aspects of the global response to the COVID-19 pandemic are enabled by the fast and open publication of SARS-CoV-2 genetic sequence data. The European Nucleotide Archive (ENA) is the European recommended open repository for genetic sequences. In this work, we present a tool for submitting raw sequencing reads of SARS-CoV-2 to ENA. The tool features a single-step submission process, a graphical user interface, tabular-formatted metadata and the possibility to remove human reads prior to submission. A Galaxy wrap of the tool allows users with little or no bioinformatics knowledge to do bulk sequencing read submissions. The tool is also packed in a Docker container to ease deployment. AVAILABILITY AND IMPLEMENTATION: CLI ENA upload tool is available at github.com/usegalaxy-eu/ena-upload-cli (DOI 10.5281/zenodo.4537621); Galaxy ENA upload tool at toolshed.g2.bx.psu.edu/view/iuc/ena_upload/382518f24d6d and github.com/galaxyproject/tools-iuc/tree/master/tools/ena_upload (development); and ENA upload Galaxy container at github.com/ELIXIR-Belgium/ena-upload-container (DOI 10.5281/zenodo.4730785).

DNA methylation repels binding of hypoxia-inducible transcription factors to maintain tumor immunotolerance.

BACKGROUND: Hypoxia is pervasive in cancer and other diseases. Cells sense and adapt to hypoxia by activating hypoxia-inducible transcription factors (HIFs), but it is still an outstanding question why cell types differ in their transcriptional response to hypoxia. RESULTS: We report that HIFs fail to bind CpG dinucleotides that are methylated in their consensus binding sequence, both in in vitro biochemical binding assays and in vivo studies of differentially methylated isogenic cell lines. Based on in silico structural modeling, we show that 5-methylcytosine indeed causes steric hindrance in the HIF binding pocket. A model wherein cell-type-specific methylation landscapes, as laid down by the differential expression and binding of other transcription factors under normoxia, control cell-type-specific hypoxia responses is observed. We also discover ectopic HIF binding sites in repeat regions which are normally methylated. Genetic and pharmacological DNA demethylation, but also cancer-associated DNA hypomethylation, expose these binding sites, inducing HIF-dependent expression of cryptic transcripts. In line with such cryptic transcripts being more prone to cause double-stranded RNA and viral mimicry, we observe low DNA methylation and high cryptic transcript expression in tumors with high immune checkpoint expression, but not in tumors with low immune checkpoint expression, where they would compromise tumor immunotolerance. In a low-immunogenic tumor model, DNA demethylation upregulates cryptic transcript expression in a HIF-dependent manner, causing immune activation and reducing tumor growth. CONCLUSIONS: Our data elucidate the mechanism underlying cell-type-specific responses to hypoxia and suggest DNA methylation and hypoxia to underlie tumor immunotolerance.

Tumour hypoxia causes DNA hypermethylation by reducing TET activity.

Hypermethylation of the promoters of tumour suppressor genes represses transcription of these genes, conferring growth advantages to cancer cells. How these changes arise is poorly understood. Here we show that the activity of oxygen-dependent ten-eleven translocation (TET) enzymes is reduced by tumour hypoxia in human and mouse cells. TET enzymes catalyse DNA demethylation through 5-methylcytosine oxidation. This reduction in activity occurs independently of hypoxia-associated alterations in TET expression, proliferation, metabolism, hypoxia-inducible factor activity or reactive oxygen species, and depends directly on oxygen shortage. Hypoxia-induced loss of TET activity increases hypermethylation at gene promoters in vitro. In patients, tumour suppressor gene promoters are markedly more methylated in hypoxic tumour tissue, independent of proliferation, stromal cell infiltration and tumour characteristics. Our data suggest that up to half of hypermethylation events are due to hypoxia, with these events conferring a selective advantage. Accordingly, increased hypoxia in mouse breast tumours increases hypermethylation, while restoration of tumour oxygenation abrogates this effect. Tumour hypoxia therefore acts as a novel regulator of DNA methylation.

HIF-1α Promotes Glutamine-Mediated Redox Homeostasis and Glycogen-Dependent Bioenergetics to Support Postimplantation Bone Cell Survival.

Cell-based therapy is a promising strategy in regenerative medicine, but the poor survival rate of the implanted cells remains a major challenge and limits clinical translation. We preconditioned periosteal cells to the hypoxic and ischemic environment of the bone defect site by deleting prolyl hydroxylase domain-containing protein 2 (PHD2), resulting in hypoxia-inducible factor 1 alpha (HIF-1α) stabilization. This strategy increased postimplantation cell survival and improved bone regeneration. The enhanced cell viability was angiogenesis independent but relied on combined changes in glutamine and glycogen metabolism. HIF-1α stabilization stimulated glutaminase-mediated glutathione synthesis, maintaining redox homeostasis at baseline and during oxidative or nutrient stress. Simultaneously, HIF-1α signaling increased glycogen storage, preventing an energy deficit during nutrient or oxygen deprivation. Pharmacological inhibition of PHD2 recapitulated the adaptations in glutamine and glycogen metabolism and, consequently, the beneficial effects on cell survival. Thus, targeting cellular metabolism is an appealing strategy for bone regeneration and cell-based therapy in general.