Uridine

Abstract: We describe a chemical method to detect RNA synthesis in cells, based on the biosynthetic incorporation of the uridine analog 5-ethynyluridine (EU) into newly transcribed RNA, on average once every 35 uridine residues in total RNA. EU-labeled cellular RNA is detected quickly and with high sensitivity by using a copper (I)-catalyzed cycloaddition reaction (often referred to as “click” chemistry) with fluorescent azides, followed by microscopic imaging. We demonstrate the use of this method in cultured cells, in which we examine the turnover of bulk RNA after EU pulses of varying lengths. We also use EU to assay transcription rates of various tissues in whole animals, both on sections and by whole-mount staining. We find that total transcription rates vary greatly among different tissues and among different cell types within organs.

Abstract: Previous studies have shown that the translation level of in vitro transcribed messenger RNA (mRNA) is enhanced when its uridines are replaced with pseudouridines; however, the reason for this enhancement has not been identified. Here, we demonstrate that in vitro transcripts containing uridine activate RNA-dependent protein kinase (PKR), which then phosphorylates translation initiation factor 2-alpha (eIF-2α), and inhibits translation. In contrast, in vitro transcribed mRNAs containing pseudouridine activate PKR to a lesser degree, and translation of pseudouridine-containing mRNAs is not repressed. RNA pull-down assays demonstrate that mRNA containing uridine is bound by PKR more efficiently than mRNA with pseudouridine. Finally, the role of PKR is validated by showing that pseudouridine- and uridine-containing RNAs were translated equally in PKR knockout cells. These results indicate that the enhanced translation of mRNAs containing pseudouridine, compared to those containing uridine, is mediated by decreased activation of PKR.

Abstract: Processes for preparing 2'-O-alkylated guanosine, uridine, cytidine, and 2,6-diaminopurine 3'-O-phosphoramidites include the steps of alkylating nucleoside precursors, adding suitable blocking groups and phosphitylating. For the guanosine 2'-O-alkylated 3'-O-phosphoramidites, alkylation is effected on 2,6-diamino-9-(β-D-ribofuranosyl)purine followed by deamination. For uridine 2'-O-alkylated 3'-O-phosphoramidites, alkylation is effect on a dialkyl stannylene derivative of uridine. For cytidine 2'-O-alkylated 3'-O-phosphoramidites, alkylation is effected directly on cytidine. Alkylation is effected directly upon 2,6-diaminopurine.