CONSTRUCTION OF A 2.8-MEGABASE YEAST ARTIFICIAL CHROMOSOME CONTIG ANDCLONING OF THE HUMAN METHYLTHIOADENOSINE PHOSPHORYLASE GENE FROM THE TUMOR-SUPPRESSOR REGION ON 9P21

Many human malignant cells lack methylthioadenosine phosphorylase (MTA P) enzyme activity, The gene (MTAP) encoding this enzyme was previousl y mapped to the short arm of chromosome 9, band p21-22, a region that is frequently deleted in multiple tumor types. To clone candidate tumo r suppressor genes from the deleted region on 9p21-22, we have constru cted a long-range physical map of 2.8 megabases for 9p21 by using over lapping yeast artificial chromosome and cosmid clones. This map includ es the type I IFN gene cluster, the recently identified candidate tumo r suppressor genes CDKN2 (p16(INK4A)) and CDKN2B (p15(INK4B)), and sev eral CpG islands, In addition, we have identified other transcription units within the yeast artificial chromosome contig. Sequence analysis of a 2,5-kb cDNA clone isolated from a CpG island that maps between t he IFN genes and CDKN2 reveals a predicted open reading frame of 283 a mino acids followed by 1302 nucleotides of 3' untranslated sequence. T his gene is evolutionarily conserved and shows significant amino acid homologies to mouse and human purine nucleoside phosphorylases and to a hypothetical 25.8 kDa protein in the pet gene (coding for cytochrome bc(1) complex) region of Rhodospirillum rubrum. The location, express ion pattern, and nucleotide sequence of this gene suggest that it code s for the MTAP enzyme.