Hypermethylated-capped selenoprotein mRNAs in mammals

• Published in: Nucleic acids research Vol. 42; no. 13; pp. 8663 - 8677
• Main Authors: Wurth, Laurence, Gribling-Burrer, Anne-Sophie, Verheggen, Céline, Leichter, Michael, Takeuchi, Akiko, Baudrey, Stéphanie, Martin, Franck, Krol, Alain, Bertrand, Edouard, Allmang, Christine
• Format: Journal Article
• Language: English
• Published: England Oxford University Press 29-07-2014
• Subjects: Cell Line; Eukaryotic Initiation Factor-4E - metabolism; Glutathione Peroxidase - biosynthesis; Glutathione Peroxidase - genetics; Humans; Methylation; Methyltransferases - metabolism; Nuclear Proteins - metabolism; Polyribosomes - chemistry; Protein Biosynthesis; Ribonucleoproteins, Small Nucleolar - metabolism; RNA; RNA Caps - metabolism; RNA, Messenger - analysis; RNA, Messenger - metabolism; RNA-Binding Proteins - metabolism; Selenoproteins - biosynthesis; Selenoproteins - genetics; Selenoproteins - metabolism; SMN Complex Proteins - metabolism
• ISSN: 0305-1048; 1362-4962
• DOI: 10.1093/nar/gku580

Mammalian mRNAs are generated by complex and coordinated biogenesis pathways and acquire 5'-end m(7)G caps that play fundamental roles in processing and translation. Here we show that several selenoprotein mRNAs are not recognized efficiently by translation initiation factor eIF4E because they bear a hypermethylated cap. This cap modification is acquired via a 5'-end maturation pathway similar to that of the small nucle(ol)ar RNAs (sn- and snoRNAs). Our findings also establish that the trimethylguanosine synthase 1 (Tgs1) interacts with selenoprotein mRNAs for cap hypermethylation and that assembly chaperones and core proteins devoted to sn- and snoRNP maturation contribute to recruiting Tgs1 to selenoprotein mRNPs. We further demonstrate that the hypermethylated-capped selenoprotein mRNAs localize to the cytoplasm, are associated with polysomes and thus translated. Moreover, we found that the activity of Tgs1, but not of eIF4E, is required for the synthesis of the GPx1 selenoprotein in vivo.