An STS in the human TNF locus located at 6p21.3.

Human genes encoding tumor necrosis factor (TNF-a) and lymphotoxin (TNF-/3) are tandemly arranged (1) and located at 6p21.3 (2, 3). Their precise position within MHC has been determined (4, 5). We recently sequenced a 820 bp fragment located 3.5 kb upstream to TNF genes centromeric to HLA-B and used the sequence surrounding the two linked microsatellites to study TNF gene polymorphism (6). We now combine information on the unique portion of this sequence to define a novel Sequence-Tagged Site (STS), designated hTNF.l/6p21.3 which can be used as a probe for retrieving DNA clones from human genomic libraries (7). Using PCR (8) a fragment of expected 437 bp size was amplified. Its sequence indicated below was in agreement with one obtained on genomic clones. When this 437 bp fragment was uniformly labeled and used to probe genomic Southern blot, a single Kpnl fragment of 6 kb was observed in agreement with physical mapping data (1, 9).