WW domain-containing FBP-30 is regulated by p53

A subtractive cloning approach was used to clone genes transcriptionally induced in thymocytes undergoing programmed cell death after gamma-irradiation. We thus identified about 60 upregulated genes. One of these genes encodes a WW domain previously briefly reported by others, which defines this gene as FBP-30. cDNA sequencing showed FBP-30 to be remarkably conserved in mammals. FBP-30 expression, essentially restricted to T cells, was regulated by p53 since it increased (1) after gamma-irradiation in wild-type but not in p53 -/- thymocytes and (2) in cells transfected with a conditional temperature-sensitive p53 mutant, less than 1 h after shifting to permissive temperature. Upregulation of FBP-30 expression thus depends upon p53 protein expression and correlates with cell death induction in these systems. While the kinetics of its induction are rapid, the observed increased expression of FBP-30 in the presence of protein synthesis inhibitors suggests that FBP-30 gene expression is indirectly regulated by p53, through downregulation of a labile inhibitor of FBP-30 expression.