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Crystal structure of Saccharomyces cerevisiae Nep1/Emg1 bound to S-adenosylhomocysteine and 1 molecule of cognate RNA
Structural highlights
FunctionNEP1_YEAST S-adenosyl-L-methionine-dependent pseudouridine N(1)-methyltransferase that methylates pseudouridine at position 1189 (Psi1189) in 18S rRNA. Involved the biosynthesis of the hypermodified N1-methyl-N3-(3-amino-3-carboxypropyl) pseudouridine (m1acp3-Psi) conserved in eukaryotic 18S rRNA. N1-methylation is independent on acp-modification at the N3-position of U1191. Has also an essential role in 40S ribosomal subunit biogenesis independent on its methyltransferase activity, facilitating the incorporation of ribosomal protein S19 (RPS19A/RPS19B) during the formation of pre-ribosomes.[1] [2] [3] [4] [5] Publication Abstract from PubMedNucleolar Essential Protein 1 (Nep1) is required for small subunit (SSU) ribosomal RNA (rRNA) maturation and is mutated in Bowen-Conradi Syndrome. Although yeast (Saccharomyces cerevisiae) Nep1 interacts with a consensus sequence found in three regions of SSU rRNA, the molecular details of the interaction are unknown. Nep1 is a SPOUT RNA methyltransferase, and can catalyze methylation at the N1 of pseudouridine. Nep1 is also involved in assembly of Rps19, an SSU ribosomal protein. Mutations in Nep1 that result in decreased methyl donor binding do not result in lethality, suggesting that enzymatic activity may not be required for function, and RNA binding may play a more important role. To study these interactions, the crystal structures of the scNep1 dimer and its complexes with RNA were determined. The results demonstrate that Nep1 recognizes its RNA site via base-specific interactions and stabilizes a stem-loop in the bound RNA. Furthermore, the RNA structure observed contradicts the predicted structures of the Nep1-binding sites within mature rRNA, suggesting that the Nep1 changes rRNA structure upon binding. Finally, a uridine base is bound in the active site of Nep1, positioned for a methyltransfer at the C5 position, supporting its role as an N1-specific pseudouridine methyltransferase. Structural insight into the functional mechanism of Nep1/Emg1 N1-specific pseudouridine methyltransferase in ribosome biogenesis.,Thomas SR, Keller CA, Szyk A, Cannon JR, Laronde-Leblanc NA Nucleic Acids Res. 2010 Nov 17. PMID:21087996[6] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. References
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