Splicing enhancement in the yeast rp51b intron

D.  LIBRI a1c1, A.  LESCURE a2 and M.  ROSBASH a3
a1 Centre National de la Recherche Scientifique, Centre de Génétique Moléculaire, Gif-sur-Yvette, France
a2 Unité Propre de Recherche 9002 Structure des Macromolécules Biologiques et Mécanismes de Réaction, 67084 Strasbourg Cedex, France
a3 Howard Hughes Medical Institute, Brandeis University, Waltham, Massachusetts 02254, USA


Splicing enhancement in higher eukaryotes has been linked to SR proteins, to U1 snRNP, and to communication between splice sites across introns or exons mediated by protein–protein interactions. It has been previously shown that, in yeast, communication mediated by RNA–RNA interactions between the two ends of introns is a basis for splicing enhancement. We designed experiments of randomization-selection to isolate splicing enhancers that would work independently from RNA secondary structures. Surprisingly, one of the two families of sequences selected was essentially composed of 5′ splice site variants. We show that this sequence enhances splicing independently of secondary structure, is exportable to heterologous contexts, and works in multiple copies with additive effects. The data argue in favor of an early role for splicing enhancement, possibly coincident with commitment complex formation. Genetic compensation experiments with U1 snRNA mutants suggest that U1 snRNP binding to noncanonical locations is required for splicing enhancement.

(Received June 10 1999)
(Revised July 21 1999)
(Accepted November 29 1999)

Key Words: enhancer; randomization-selection; splicing; U1 snRNP.

c1 Reprint requests to: D. Libri, Centre National de la Recherche Scientifique, C.G.M., Gif-sur-Yvette, France; e-mail: Libri@cgm.cnrs-gif.fr.