ISOLATION OF 4 HSP70 GENES IN THE PIG AND LOCALIZATION ON CHROMOSOMES-7 AND CHROMOSOME-14

For insight into the general organization of the swine leukocyte antig en (SLA) complex, the swine major histocompatibility complex (MHC), fo ur sequences related to the heat-shock proteins HSP70 were characteriz ed by screening of a pig genomic cosmid library with a swine cDNA HSP7 0 2.6-kb probe. This yielded three positive clones: HC2.2, HC3.2, and HC4.2. Restriction site maps revealed a large overlap of HC2.2 with HC 3.2, whereas HC4.2 was independent. Southern blot hybridization with t he 5' section, the central section, and the 3' section of the 2.6-kb p robe and also with a swine 4.5-kb HSP70 genomic probe suggested the ex istence, within the overlapping clones, of three distinct HSP70 sequen ces encompassing a segment no longer than 22 kb. The HC4.2 clone, whic h hybridized with the same probes, displayed a single band of 7.3 kb, probably corresponding to one gene only. Fluorescent in situ hybridiza tion on swine chromosome metaphases with the whole HC2.2 or HC4.2 cosm ids allowed the assignment of HC2.2 to MHC region on Chromosome (Chr) 7 (Cen-p 1.1), and of HC4.2 to Chr 14 (q2.4-2.5). Thus, as in humans, the swine MHC comprises three closely linked HSP70 loci. The presence of additional genes belonging to the same inducible HSP70 gene family can be expected from what is known in humans. The HSP70 gene found her e on the pig Chr 14 may be one of these putative unidentified genes.