CHARACTERIZATION OF 4 YEAST ARTIFICIAL CHROMOSOME CLONES MAPPED TO HUMAN-CHROMOSOME 21Q22.1 WITH 8 MARKERS

Yeast artificial chromosome (YAC) clones have been successfully utiliz ed to generate a YAC contig map of the long arm of human chromosome 21 (Hu21q). The chromosome subband of 21q22.1 where five genetic loci (I FNAR1, IFNAR2, CRFB4, AF-1, and GART) are mapped is a gene-rich region and needs to be characterized in further detail. YAC D 142H8 and YAC F136C5, which were characterized previously by a functional YAC expres sion procedure, and two new YAC clones, YAC 872B5 and YAC 876D4 locate d at 21q22.1 whose YAC sizes are 800 kb and 1,500 kb, respectively, we re used in this study. To obtain more markers useful for making a deta iled physical map of the region, a purified yeast artificial chromosom e (YAC D142H8) was used to screen the 3 x 1 S cDNA library. As a resul t three anonymous cDNA clones (Kmy1, Kmy2, and Qorf4) were obtained, a nd the nucleotide sequences of Kmy1 and Kmy2 were determined. In an at tempt to make a detailed physical map of the region, the locations of five known genes as well as the three new markers were determined on t he four YACs by Southern blot analysis. YAC 872B5 contained all marker s except GART while YAC F136C5, YAC D142H8, and YAC 876D4 contained th ree markers (CRFB4, IFNAR1, and IFNAR2), four markers (Kmy1, Kmy2, Qor f4 and AF-1), and four markers (Kmy1, Kmy2, Qorf4 and GART), respectiv ely. YAC 872B5 may represent 1,500 kb of the 21q22.1 subband and half of the 3 x 1 S region, so it should be very useful for studying the re levent region of the human chromosome functionally and physically.