title: Structural basis for dual roles of Aar2p in U5 snRNP assembly.
abstract: Yeast U5 small nuclear ribonucleoprotein particle (snRNP) is assembled via a cytoplasmic precursor that contains the U5-specific Prp8 protein but lacks the U5-specific Brr2 helicase. Instead, pre-U5 snRNP includes the Aar2 protein not found in mature U5 snRNP or spliceosomes. Aar2p and Brr2p bind competitively to a C-terminal region of Prp8p that comprises consecutive RNase H-like and Jab1/MPN-like domains. To elucidate the molecular basis for this competition, we determined the crystal structure of Aar2p in complex with the Prp8p RNase H and Jab1/MPN domains. Aar2p binds on one side of the RNase H domain and extends its C terminus to the other side, where the Jab1/MPN domain is docked onto a composite Aar2p-RNase H platform. Known Brr2p interaction sites of the Jab1/MPN domain remain available, suggesting that Aar2p-mediated compaction of the Prp8p domains sterically interferes with Brr2p binding. Moreover, Aar2p occupies known RNA-binding sites of the RNase H domain, and Aar2p interferes with binding of U4/U6 di-snRNA to the Prp8p C-terminal region. Structural and functional analyses of phospho-mimetic mutations reveal how phosphorylation reduces affinity of Aar2p for Prp8p and allows Brr2p and U4/U6 binding. Our results show how Aar2p regulates both protein and RNA binding to Prp8p during U5 snRNP assembly.
authors: Fachbereich Biologie/Chemie/Pharmazie, Abteilung Strukturbiochemie, Freie Universität Berlin, D-14195 Berlin, Germany. gweber@chemie.fu-berlin.de
authors: Gert
authors: G
authors: Weber
authors: Vanessa F
authors: VF
authors: Cristão
authors: Karine F
authors: KF
authors: Santos
authors: Sina Mozaffari
authors: SM
authors: Jovin
authors: Anna C
authors: AC
authors: Heroven
authors: Nicole
authors: N
authors: Holton
authors: Reinhard
authors: R
authors: Lührmann
authors: Jean D
authors: JD
authors: Beggs
authors: Markus C
authors: MC
authors: Wahl
mesh_terms: D002470:Cell Survival; D008958:Models, Molecular; D009154:Mutation; D009687:Nuclear Proteins / Q000737:chemistry* / Q000378:metabolism*; D010766:Phosphorylation; D011485:Protein Binding; D020836:Protein Structure, Quaternary; D017434:Protein Structure, Tertiary; D017415:Ribonucleoprotein, U5 Small Nuclear / Q000737:chemistry* / Q000378:metabolism*; D012441:Saccharomyces cerevisiae / Q000378:metabolism*; D029701:Saccharomyces cerevisiae Proteins / Q000737:chemistry* / Q000378:metabolism*
chemical_list: C440573:Aar2p protein, S cerevisiae; D009687:Nuclear Proteins; D017415:Ribonucleoprotein, U5 Small Nuclear; D029701:Saccharomyces cerevisiae Proteins