Relevance of the lariat model to the splicing of the H-2 gene family.

We examined the splicing of the H-2 gene family, taking the H-2Kd as a prototype, in the framework of the lariat model. We mainly investigated the mechanism described by Konarska et al. [Nature (Lond.) 313, 552-557 (1985)] who propose a direct interaction between the 5' splicing site and the branching region. We also checked each of the H-2 introns for the presence of patterns resembling the published consensus for the branching region. The known splicing events in the H-2 gene family are not always consistent with the current models, and our results indicate that slightly different mechanisms govern the splicing of different introns. A tentative explanation of the alternative splicing of the first and last intron, previously described, is given. The removal of the large third intron is not easily rationalized unless new rules for an additional multistep processing are postulated.