Cancer stem cells (CSCs) are a small but critical cell population for cancer biology since they display inherent resistance to standard therapies and give rise to metastases. Despite accruing evidence establishing a link between deregulation of epitranscriptome-related players and tumorigenic process, the role of messenger RNA (mRNA) modifications in the regulation of CSC properties remains poorly understood. Here, we show that the cytoplasmic pool of fat mass and obesity-associated protein (FTO) impedes CSC abilities in colorectal cancer through its N6,2’-O-dimethyladenosine (m6Am) demethylase activity. While m6Am is strategically located next to the m7G-mRNA cap, its biological function is not well understood and has not been addressed in cancer. Low FTO expression in patient-derived cell lines elevates m6Am level in mRNA which results in enhanced in vivo tumorigenicity and chemoresistance. Inhibition of the nuclear m6Am methyltransferase, PCIF1/CAPAM, fully reverses this phenotype, stressing the role of m6Am modification in stem-like properties acquisition. FTO-mediated regulation of m6Am marking constitutes a reversible pathway controlling CSC abilities. Altogether, our findings bring to light the first biological function of the m6Am modification and its potential adverse consequences for colorectal cancer management.

Growing evidence suggests that human gut bacteria, which comprise the microbiome, are linked to several neurodegenerative disorders. An imbalance in the bacterial population in the gut of Parkinson’s disease (PD) and Alzheimer’s disease (AD) patients has been detected in several studies. This dysbiosis very likely decreases or increases microbiome-derived molecules that are protective or detrimental, respectively, to the human body and those changes are communicated to the brain through the so-called ‘gut-brain-axis’. The microbiome-derived molecule queuine is a hypermodified nucleobase enriched in the brain and is exclusively produced by bacteria and salvaged by humans through their gut epithelium. Queuine replaces guanine at the wobble position (position 34) of tRNAs with GUN anticodons and promotes efficient cytoplasmic and mitochondrial mRNA translation. Queuine depletion leads to protein misfolding and activation of the endoplasmic reticulum stress and unfolded protein response pathways in mice and human cells. Protein aggregation and mitochondrial impairment are often associated with neural dysfunction and neurodegeneration. To elucidate whether queuine could facilitate protein folding and prevent aggregation and mitochondrial defects that lead to proteinopathy, we tested the effect of chemically synthesized queuine, STL-101, in several in vitro models of neurodegeneration. After neurons were pretreated with STL-101 we observed a significant decrease in hyperphosphorylated alpha-synuclein, a marker of alpha-synuclein aggregation in a PD model of synucleinopathy, as well as a decrease in tau hyperphosphorylation in an acute and a chronic model of AD. Additionally, an associated increase in neuronal survival was found in cells pretreated with STL-101 in both AD models as well as in a neurotoxic model of PD. Measurement of queuine in the plasma of 180 neurologically healthy individuals suggests that healthy humans maintain protective levels of queuine. Our work has identified a new role for queuine in neuroprotection uncovering a therapeutic potential for STL-101 in neurological disorders.

20Cancer stem cells (CSCs) are a small but critical cell population for cancer biology since they display 21 inherent resistance to standard therapies and give rise to metastases. Despite accruing evidence 22 establishing a link between deregulation of epitranscriptome-related players and tumorigenic 23 process, the role of messenger RNA (mRNA) modifications dynamic in the regulation of CSC 24 properties remains poorly understood. Here, we show that the cytoplasmic pool of fat mass and 25 obesity-associated protein (FTO) impedes CSC abilities in colorectal cancer through its m 6 Am (N 6 ,2'-26 O-dimethyladenosine) demethylase activity. While m 6 Am is strategically located next to the m 7 G-27 mRNA cap, its biological function is not well understood and has not been addressed in cancer. Low 28 FTO expression in patient-derived cell lines elevates m 6 Am level in mRNA which results in enhanced 29 in vivo tumorigenicity and chemoresistance. Inhibition of the nuclear m 6 Am methyltransferase, 30 PCIF1/CAPAM, partially reverses this phenotype. FTO-mediated regulation of m 6 Am marking 31 constitutes a novel, reversible pathway controlling CSC abilities that does not involve transcriptome 32 remodeling, but could fine-tune translation efficiency of selected m 6 Am marked transcripts. 33 Altogether, our findings bring to light the first biological function of the m 6 Am modification and its 34 potential adverse consequences for colorectal cancer management. 35 36 Despite significant advances in diagnosis and therapy, colorectal cancer (CRC) remains a major 37 cause of mortality and morbidity worldwide. CRC survival is highly dependent upon early diagnosis. 38 Patients with localized cancer exhibit 70 to 90% 5-year survival. Survival from metastatic cancer 39 plummets to 10%. Metastasis is a multistep process encompassing local infiltration of tumor cells into 40 adjacent tissues, transendothelial migration into vessels, survival in the circulatory system, 41 extravasation, and colonization of secondary organs [1]. This process entails constant reprogramming 42 of gene expression to enable tumor adaptation in different environments, a peculiar trait of cancer 43 stem cells (CSCs). CSC constitute a minor subpopulation of tumor cells endowed with self-renewal and 44 multi-lineage differentiation capacity [2]. The most clinically relevant trait of CSCs is their ability to 45 metastasize and escape from standard chemotherapy [3]. Understanding the molecular mechanisms 46 that participate to the CSC phenotype is critical to designing improved cancer therapeutics. 47 Discovered several decades ago [12-16], the function of m 6 A remained obscure until the identification 55 of the first m 6 A demethylase, the fat mass and obesity-associated protein (FTO) [17]. The marriage of 56 immunochemical approaches with next-generation sequencing (NGS) technologies revealed the 57 unique topology of m 6 A distribution along mRNA. m 6 A is a dynamic reversible chemical modification 58 catalyzed by a protein complex consisting of the methyl...