Figure 6.

A model summarizing interactions between Mer1p and splicing factors during the formation of early splicing complexes. In this model, Mer1p stimulates the formation of these early splicing complexes on pre-mRNAs that contain the Mer1p splicing enhancer or prevents the dissociation of these early splicing complexes such that spliceosome assembly can progress to the formation of an active spliceosome. Proteins that interact with Mer1p by two-hybrid analysis are indicated by a lightning bolt between the protein and Mer1p. Thicker bolts indicate stronger two-hybrid interactions. Proteins that cross-link to the 5′ splice site region of pre-mRNA are indicated by a red X. Proteins required for Mer1p to activate splicing, but for which no direct physical interaction with Mer1p can be detected, are connected to Mer1p with orange arrows. The branch point adenosine of the pre-mRNA is indicated by an A, and the enhancer element is colored red.