“…The 5′ end of all eukaryotic mRNAs is defined by a cap structure consisting of N7-guanosine (m 7 G) joined by a 5′,5′-triphosphate linkage to the first transcribed nucleotide. The m 7 GpppN cap structure (where N is the first transcribed nucleotide) was first identified in the 1970s through studies of viral RNAs and later as a common feature of all eukaryotic mRNAs (Furuichi, 2015; Furuichi et al, 1975; Furuichi, Morgan, Muthukrishnan, & Shatkin, 1975; Furuichi et al, 1975; Moss, 2017; Wei & Moss, 1975; Wei, Gershowitz, & Moss, 1975). A number of recent reviews have covered the nuclear steps involved in cotranscriptional capping of pre-mRNAs (Cowling, 2010; Ghosh & Lima, 2010; Ramanathan, Robb, & Chan, 2016) and the role of the cap in downstream processes including translation, mRNA turnover, and nonsense-mediated mRNA decay (Topisirovic, Svitkin, Sonenberg, & Shatkin, 2011; Grudzien-Nogalska & Kiledjian, 2017).…”