STRUCTURAL-ANALYSIS OF THE HLA-A HLA-F SUBREGION - PRECISE LOCALIZATION OF 2 NEW MULTIGENE FAMILIES CLOSELY ASSOCIATED WITH THE HLA CLASS-ISEQUENCES/

Positional cloning strategies for the hemochromatosis gene have previo usly concentrated on a target area restricted to a maximum genomic exp anse of 400 kb around the HLA-A and HLA-F loci. Recently, the candidat e region has been extended to 2-3 Mb on the distal side of the MHC. In this study, 10 coding sequences [hemochromatosis candidate genes (HCG ) I to X] were isolated by cDNA selection using YACs covering the HLA- A/HLA-F subregion. Two of these (HCG II and HCG IV) belong to multigen e families, as well as other sequences already described in this regio n, i.e., P5, pMC 6.7, and HLA class I. Fingerprinting of the four YACs overlapping the region was performed and allowed partial localization of the different multigene family sequences on each YAC without defin ing their exact positions. Fingerprinting on cosmids isolated from the ICRF chromosome B-specific cosmid library allowed more precise locali zation of the redundant sequences in all of the multigene families and revealed their apparent organization in clusters. Further examination of these intertwined sequences demonstrated that this structural orga nization resulted from a succession of complex phenomena, including du plications and contractions. This study presents a precise description of the structural organization of the HLA-A/HLA-F region and a determ ination of the sequences involved in the megabase size polymorphism ob served among the A3, A24, and A31 haplotypes. (C) 1996 Academic Press, Inc.