Structurally conserved Nop56/58 N-terminal domain facilitates archaeal box C/D ribonucleoprotein-guided methyltransferase activity |
| |
Authors: | Gagnon Keith T Biswas Shyamasri Zhang Xinxin Brown Bernard A Wollenzien Paul Mattos Carla Maxwell E Stuart |
| |
Institution: | Department of Molecular and Structural Biochemistry, North Carolina State University, Raleigh, North Carolina 27695, USA. |
| |
Abstract: | Box C/D RNA-protein complexes (RNPs) guide the 2′-O-methylation of nucleotides in both archaeal and eukaryotic ribosomal RNAs. The archaeal box C/D and C′/D′ RNP subcomplexes are each assembled with three sRNP core proteins. The archaeal Nop56/58 core protein mediates crucial protein-protein interactions required for both sRNP assembly and the methyltransferase reaction by bridging the L7Ae and fibrillarin core proteins. The interaction of Methanocaldococcus jannaschii (Mj) Nop56/58 with the methyltransferase fibrillarin has been investigated using site-directed mutagenesis of specific amino acids in the N-terminal domain of Nop56/58 that interacts with fibrillarin. Extensive mutagenesis revealed an unusually strong Nop56/58-fibrillarin interaction. Only deletion of the NTD itself prevented dimerization with fibrillarin. The extreme stability of the Nop56/58-fibrillarin heterodimer was confirmed in both chemical and thermal denaturation analyses. However, mutations that did not affect Nop56/58 binding to fibrillarin or sRNP assembly nevertheless disrupted sRNP-guided nucleotide modification, revealing a role for Nop56/58 in methyltransferase activity. This conclusion was supported with the cross-linking of Nop56/58 to the target RNA substrate. The Mj Nop56/58 NTD was further characterized by solving its three-dimensional crystal structure to a resolution of 1.7 Å. Despite low primary sequence conservation among the archaeal Nop56/58 homologs, the overall structure of the archaeal NTD domain is very well conserved. In conclusion, the archaeal Nop56/58 NTD exhibits a conserved domain structure whose exceptionally stable interaction with fibrillarin plays a role in both RNP assembly and methyltransferase activity. |
| |
Keywords: | Fibrillin Protein-Protein Interactions Ribonuclear Protein (RNP) Ribosomal RNA (rRNA) RNA Methylation Nop56/58 Box C/D RNA Methyltransferase |
本文献已被 PubMed 等数据库收录! |
|