Pur alpha is a 39-kDa sequence-specific single-stranded DNA/RNA binding protein with the ability to modulate transcription of several genes containing the Pur element in their promoter region. Human and mouse Pur alpha exhibit an extraordinary degree of conservation with only two changes at amino acid residues 49 and 306. A 15-kb genomic clone encompassing the mouse Pur alpha gene was isolated by screening the mouse genomic library, using a PCR-amplified fragment from human Pur alpha cDNA. Results from sequencing analysis confirmed the isolated genomic clone to be Pur alpha and not the other members of the Pur family, including Pur beta. Characterization of the mouse Pur alpha gene by restriction analysis/Southern blotting and sequencing revealed that the Pur alpha gene contains only one intron within the 5' UTR and the open reading frame was intact. Using chromosomal markers, the Pur alpha gene was mapped to chromosome 18 in mouse and rat. J. Cell. Biochem. 77:1-5, 2000. (C) 2000 Wiley-Liss, Inc.