Tet-enzyme-mediated 5-hydroxymethylation of cytosines in DNA plays a crucial role in mouse embryonic stem cells (ESCs). In RNA also, 5-hydroxymethylcytosine (5hmC) has recently been evidenced, but its physiological roles are still largely unknown. Here we show the contribution and function of this mark in mouse ESCs and differentiating embryoid bodies. Transcriptome-wide mapping in ESCs reveals hundreds of messenger RNAs marked by 5hmC at sites characterized by a defined unique consensus sequence and particular features. During differentiation a large number of transcripts, including many encoding key pluripotency-related factors (such as Eed and Jarid2), show decreased cytosine hydroxymethylation. Using Tet-knockout ESCs, we find Tet enzymes to be partly responsible for deposition of 5hmC in mRNA. A transcriptome-wide search further reveals mRNA targets to which Tet1 and Tet2 bind, at sites showing a topology similar to that of 5hmC sites. Tet-mediated RNA hydroxymethylation is found to reduce the stability of crucial pluripotency-promoting transcripts. We propose that RNA cytosine 5-hydroxymethylation by Tets is a mark of transcriptome flexibility, inextricably linked to the balance between pluripotency and lineage commitment.

Fungal virulence is regulated by a tight interplay of transcriptional control and chromatin remodelling. Despite compelling evidence that lysine acetylation modulates virulence of pathogenic fungi such as Candida albicans , the underlying mechanisms have remained largely unexplored. We report here that Gcn5, a paradigm lysyl-acetyl transferase (KAT) modifying both histone and non-histone targets, controls fungal morphogenesis – a key virulence factor of C . albicans . Our data show that genetic removal of GCN5 abrogates fungal virulence in mice, suggesting strongly diminished fungal fitness in vivo . This may at least in part arise from increased susceptibility to killing by macrophages, as well as by other phagocytes such as neutrophils or monocytes. Loss of GCN5 also causes hypersensitivity to the fungicidal drug caspofungin. Caspofungin hypersusceptibility requires the master regulator Efg1, working in concert with Gcn5. Moreover, Gcn5 regulates multiple independent pathways, including adhesion, cell wall-mediated MAP kinase signaling, hypersensitivity to host-derived oxidative stress, and regulation of the Fks1 glucan synthase, all of which play critical roles in virulence and antifungal susceptibility. Hence, Gcn5 regulates fungal virulence through multiple mechanisms, suggesting that specific inhibition of Gcn5 could offer new therapeutic strategies to combat invasive fungal infections.

rowing evidence suggests that chemical modifications on RNA, similar to those on DNA or histones, control gene expression 1 . More than 100 types of RNA modifications have been reported 2 , among which m 6 A is the most abundant internal modification 3 . Transcriptome-wide mappings of m 6 A identified methylated sites in more than 7,000 mRNA transcripts, many conserved between humans and mice 3,4 . Marking with m 6 A occurs on adenosines embedded in the consensus sequence G(G > A) m 6 ACU, especially in 3′-untranslated regions (UTRs) near stop codons of transcripts 5 . Installed by the METTL3/METTL14/WTAP methyltransferase complex and erased by the demethylases FTO and ALKBH5 (refs. 6,7 ), m 6 A influences fundamental aspects of mRNA metabolism, such as mRNA stability, splicing, transport and translation, thereby impacting gene expression [3][4][5][8][9][10][11][12] .FTO was found to catalyze m 6 A demethylation in an Fe(II)-and α-ketoglutarate-dependent enzymatic reaction 6,13,14 . In addition to an involvement in essential biological processes 5,8 , FTO has been linked to cancer, acting as an oncoprotein in leukemia 15,16 . Despite conflicting results by Vu et al., who observed no substantial effect of FTO depletion on acute myeloid leukemia (AML) cell viability 17 , the development of FTO inhibitors has since shown encouraging results in preclinical settings 16,18,19 . Similar oncogene functions were

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