Mammalian Y RNAs are modified at discrete guanosine residues with N-glycans

Abstract

Glycans modify lipids and proteins to mediate inter-and intramolecular interactions across all domains of life. RNA, another multifaceted biopolymer, is not thought to be a major target of glycosylation. Here, we challenge this view with evidence that mammalian cells use RNA as a third scaffold for glycosylation in the secretory pathway. Using a battery of chemical and biochemical approaches, we find that a select group of small noncoding RNAs including Y RNAs are modified with complex, sialylated N-glycans (glycoRNAs). These glycoRNA are present in multiple cell types and mammalian species, both in cultured cells and in vivo. Finally, we find that RNA glycosylation depends on the canonical N-glycan biosynthetic machinery within the ER/Golgi luminal spaces. Collectively, these findings suggest the existence of a ubiquitous interface of RNA biology and glycobiology suggesting an expanded role for glycosylation beyond canonical lipid and protein scaffolds. MAINGlycans have been shown to regulate a wide array of critical biological processes, ranging from cell-cell contacts to host-pathogen interactions, and even the organization of multicellular organisms(1). In a traditionally adjacent field of study, RNA represents another biopolymer that is central to all known life. While the building blocks of RNA are canonically limited to four bases, post-transcriptional modifications (PTMs) can dramatically elaborate the chemical diversity of RNA, with >100 identified PTMs(2-4). The cellular role for RNA is more complex than that of a simple messenger. For instance, RNAs function as scaffolds, molecular decoys, enzymes, and network regulators across the nucleus and cytosol(5-7). With the exception of a few monosaccharide-based tRNA modifications (8,9), there has been no evidence of a direct interface between these two fields of biology.

Biological Functions and Analytical Strategies of Sialic Acids in Tumor

“…Therefore, Ac 4 ManNAz has been widely used in the cell surface sialic acid labeling, such as the sialoglycoprotein expression upon megakaryocytic differentiation [135], imaging the glycosylation state of cell surface glycoproteins [136], single cell [137] or selective cell [138] metabolic glycan labeling, imaging sialyl glycomics during zebrafish development [139]. Amazingly, using an Ac 4 ManNAz metabolic labeling strategy, sialylated N-glycans on a select group of small noncoding RNAs (glycoRNAs), including Y RNAs, have been observed in mammalian cells [140], which may update our knowledge towards biochemistry, as we already know [141]. It is worth noting that per-O-acetylated monosaccharides can spontaneously react with numerous cysteines in proteomes with non-enzymatic catalysis, resulting in abnormal S-glycosylation [142].…”

HITS-CLIP analysis of human ALKBH8 points towards its role in tRNA and noncoding RNA regulation

“…Other ncRNAs, namely vault RNA, Y RNA and 7SK RNA , that were identified in our HITS-CLIP data, had previously been identified in other CLIP-seq experiments with the RNA modifier enzymes Pus7 pseudouridinylase (Guzzi et al 2018), METTL16 N 6 -adenosine methyltransferase (Warda et al 2017) or Nsun2 5-methylcytosine transferase (Hussain et al 2013). Interestingly, Y RNAs were discovered to be modified with N-glycans (Flynn et al 2019). Substantial research is needed to reveal all the modifications that are likely present in these RNAs.…”

Cell segmentation-free inference of cell types fromin situtranscriptomics data

“…Such an intracellular spatial organization of the transcriptome is often an important form of post-transcriptional regulation (Flynn et al, 2019) and imaging-based methods can reveal this organization (Battich et al, 2013). Thus, SSAM can be used to identify and investigate organization of mRNAs.…”