Characterization of four yeast artificial chromosome clones mapped to human chromosome 21q22.1 with eight markers.

Yeast artificial chromosome (YAC) clones have been successfully utilized 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 (IFNAR1, IFNAR2, CRFB4, AF-1, and GART) are mapped is a gene-rich region and needs to be characterized in further detail. YAC D142H8 and YAC F136C5, which were characterized previously by a functional YAC expression procedure, and two new YAC clones, YAC 872B5 and YAC 876D4 located at 21q22.1 whose YAC sizes are 800 kb and 1,500 kb, respectively, were used in this study. To obtain more markers useful for making a detailed physical map of the region, a purified yeast artificial chromosome (YAC D142H8) was used to screen the 3 x 1 S cDNA library. As a result three anonymous cDNA clones (Kmy1, Kmy2, and Qorf4) were obtained, and the nucleotide sequences of Kmy1 and Kmy2 were determined. In an attempt 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 the four YACs by Southern blot analysis. YAC 872B5 contained all markers except GART while YAC F136C5, YAC D142H8, and YAC 876D4 contained three markers (CRFB4, IFNAR1, and IFNAR2), four markers (Kmy1, Kmy2, Qorf4 and AF-1), and four markers (Kmy1, Kmy2, Qorf4 and GART), respectively. 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 relevent region of the human chromosome functionally and physically.