SUNY at Albany
June 19-23, 2001
Structural Basis for Recognition of Intron Branch Site RNA by SF1
An initial step during spliceosome assembly involves the formation of a multimeric protein/RNA complex which bridges the 5¢ and 3¢ intron splice sites. While the U1 snRNP assembles at the 5¢ splice site, two splicing factors, SF1 (Splicing Factor 1) and the large subunit of U2AF (U2 auxiliary factor p65, U2AF65) interact with each other and cooperatively bind to pre-mRNA intron sequences which are located near the 3¢ splice site. SF1 recognizes the intron branch site, which is almost invariant in yeast (UACUAAC) and less conserved in mammals (YNCURAY).
We have determined the three-dimensional structure of the RNA binding region of SF1 in complex with a single-stranded branch site RNA ligand using heteronuclear multidimensional NMR spectroscopy. Numerous intermolecular NOEs provide a detailed view of the protein/RNA interface. The RNA binding surface is very hydrophobic and comprises helices alpha 1, alpha 2 and strand beta 2 of the SF1 KH domain, but it also includes an additional C-terminal homology region. The recognition of the RNA is consistent with point mutations which have been shown to affect RNA binding. Our structure of the SF1/RNA complex provides the first molecular view for sequence specific recognition of the splicing branch site and has interesting implications for pre-spliceosome assembly.
Ingrid Luyten*, Zhihong Liu*, Matthew Bottomley, Katia Zanier, Remco Sprangers, Ana Messias, Angela Krämer+ and Michael Sattler**
Struc. & Comp. Bio., EMBL, Meyerhofstr. 1, D-69117 Heidelberg, Germany. P: +49 6221 387 552; F: +49 6221 387 306; sattler@EMBL-Heidelberg.de +Univ. Geneva, Dep. Cell Bio., CH-1211 Geneva 4, Switzerland. *These authors contributed equally to this work.