Structure, phosphorylation and U2AF65 binding of the N-terminal domain of splicing factor 1 during 3'-splice site recognition.Zhang, Y., Madl, T., Bagdiul, I., Kern, T., Kang, H.S., Zou, P., Mausbacher, N., Sieber, S.A., Kramer, A., Sattler, M.
(2013) Nucleic Acids Res 41: 1343-1354
- PubMed: 23175611
- DOI: https://doi.org/10.1093/nar/gks1097
- Primary Citation of Related Structures:
- PubMed Abstract:
Recognition of the 3'-splice site is a key step in pre-mRNA splicing and accomplished by a dynamic complex comprising splicing factor 1 (SF1) and the U2 snRNP auxiliary factor 65-kDa subunit (U2AF65). Both proteins mediate protein-protein and protein-RNA interactions for cooperative RNA-binding during spliceosome assembly. Here, we report the solution structure of a novel helix-hairpin domain in the N-terminal region of SF1 (SF1(NTD)). The nuclear magnetic resonance- and small-angle X-ray scattering-derived structure of a complex of the SF1(NTD) with the C-terminal U2AF homology motif domain of U2AF65 (U2AF65(UHM)) reveals that, in addition to the known U2AF65(UHM)-SF1 interaction, the helix-hairpin domain forms a secondary, hydrophobic interface with U2AF65(UHM), which locks the orientation of the two subunits. Mutational analysis shows that the helix hairpin is essential for cooperative formation of the ternary SF1-U2AF65-RNA complex. We further show that tandem serine phosphorylation of a conserved Ser80-Pro81-Ser82-Pro83 motif rigidifies a long unstructured linker in the SF1 helix hairpin. Phosphorylation does not significantly alter the overall conformations of SF1, SF1-U2AF65 or the SF1-U2AF65-RNA complexes, but slightly enhances RNA binding. Our results indicate that the helix-hairpin domain of SF1 is required for cooperative 3'-splice site recognition presumably by stabilizing a unique quaternary arrangement of the SF1-U2AF65-RNA complex.
Institute of Structural Biology, Helmholtz Zentrum München, 85764 Neuherberg, Germany.