NONHOMOLOGOUS RECOMBINATION WITHIN THE MAJOR HISTOCOMPATIBILITY COMPLEX CREATES A TRANSCRIBED HYBRID SEQUENCE

The P5-1 cDNA clone maps to the human MHC class I region (Vernet et al . 1993a). In this paper, we show that the P5-1 cDNA represents a chime ric transcript in which the first exon of an MHC class I gene has been spliced to an unrelated sequence. The corresponding gene P5-1 is comp osed of the 5' sequence of an MHC class I gene including the promoter region, the first exon, and the half of the first intron fused to an u nrelated intron, followed by a large exon. Furthermore, the non-class I part of P5-1 is present within the MHC class I region in multiple co pies, defining the P5 family. Another member of the P5 family is fused to a class I gene, although by a type of rearrangement different from P5-1. These two fusion events between members of HLA class I and P5 f amilies reflect the existence of a duplication unit including two clas s I genes and a P5 sequence. These data shed light on the MHC class I evolution and on the creation and evolution of new genes.