Alternative models for U2 snRNP involvement in the splicing of a subset of minor introns. (A) Schematic representation of putative interactions between the U2 and U12 snRNPs. These interactions could be either direct or involve additional factor(s) related (Zrsr2) or not to the U2AF complex. The 65K protein involved in the bridging of the U11 and U12 snRNPs is shown. The exon definition model accounting for the need of a major 5′ splice site for efficient splicing of the upstream minor intron (Wu and Krainer 1996) is also depicted. (B) Schematic representation of putative interactions between the U2 and U11 snRNPs. These interactions could involve the 59K protein of the U11 snRNP and components of the U2 snRNP such as SF3B1, as recently proposed (Olthof et al. 2021).
