5′ end nicotinamide adenine dinucleotide cap in human cells promotes Rna decay through DXO-mediated deNADding

• Xinfu Jiao ^[1] ; Selom K. Doamekpor ^[2] ; Jeremy G. Bird ^[1]
  1. [1] Rutgers University

     Rutgers University

     City of New Brunswick, Estados Unidos

     
  2. [2] Columbia University

     Columbia University

     Estados Unidos

     
• Localización: Cell, ISSN 0092-8674, Vol. 168, Nº. 6, 2017, págs. 1015-1027
• Idioma: inglés
• Texto completo no disponible (Saber más ...)
• Resumen

  • Eukaryotic mRNAs generally possess a 5′ end N7 methyl guanosine (m7G) cap that promotes their translation and stability. However, mammalian mRNAs can also carry a 5′ end nicotinamide adenine dinucleotide (NAD+) cap that, in contrast to the m7G cap, does not support translation but instead promotes mRNA decay. The mammalian and fungal noncanonical DXO/Rai1 decapping enzymes efficiently remove NAD+ caps, and cocrystal structures of DXO/Rai1 with 3′-NADP+ illuminate the molecular mechanism for how the “deNADding” reaction produces NAD+ and 5′ phosphate RNA. Removal of DXO from cells increases NAD+-capped mRNA levels and enables detection of NAD+-capped intronic small nucleolar RNAs (snoRNAs), suggesting NAD+ caps can be added to 5′-processed termini. Our findings establish NAD+ as an alternative mammalian RNA cap and DXO as a deNADding enzyme modulating cellular levels of NAD+-capped RNAs. Collectively, these data reveal that mammalian RNAs can harbor a 5′ end modification distinct from the classical m7G cap that promotes rather than inhibits RNA decay.