YAC CONTIG ORGANIZATION AND CPG ISLAND ANALYSIS IN XQ28

One hundred nineteen YACs were assembled into 6 contigs spanning about 7.1 Mb of Xq28. The contigs were formatted with 65 STSs and 136 hybri dization probes and were extensive enough to be aligned and oriented b y published genetic linkage and somatic cell hybrid panel data. Select ed YACs from the entire region were mapped with five rare-cutter restr iction enzymes to infer the position of putative CpG islands indicativ e of gene locations; 48 such sites were identified by the near-coincid ence of at least three rare-cutter sites. The analysis defined three s ubregions of Xq28: 4 Mb of moderate GC and CpG island content from the Xq27 border through the GABRA locus; 1.5 to 2 Mb, extending to the G6 PD gene, that is variably and poorly cloned, but contains a high conce ntration of CpG islands and GC; and about 1.5 Mb between G6PD and the telomere, which is generally low in CpG and GC levels, including a sub telomeric DNA region that shows extensive homology to Yq DNA. (C) 1994 Academic Press, Inc.