Mutations of PTEN, a tumor suppressor gene located on chromosome 10, which encodes a protein-tyrosine and lipid-phosphatase, are prevalent in various human cancers, including glioblastoma. Despite extensive characterization of PTEN mutations in human cancers and a relatively good understanding of the molecular roles of PTEN in the control of cellular processes, little is known about modes of PTEN regulation. To understand the regulation of expression of the tumor suppressor gene PTEN, we isolated a 2212 by fragment from the human BAC clone 46B12 DNA. The 3' end of this fragment starts at the Not I site of -745 relative to the first translation codon ATG (+1) and ends at the Sal I site of -2957 at the 5' end. Using classical 5'RACE and primer extension techniques, nine start sites were observed between -817 and -984 upstream of the ATG start site. We located a 137 by fragment (-958/-821) as the minimum promoter region using promoter deletion and luciferase assays. A 704 by fragment (-331-737) downstream of the 2212 by fragment was also cloned. As indicated by luciferase assays, the data show that this region possesses no promoter function. Interestingly, a p53 binding sequence is located within the 599 by fragment (-1344/-745), although p53 expression had a minimal effect on PTEN, demonstrating its insignificant role in PTEN gene expression. (C) 2002 Elsevier Science (USA).