Functional

The product of suppressor gene p53 activates transcription of target genes through specific binding to p53-responsive elements. We tested DNA-binding and trans-activating properties of wild-type and mutant p53 with a number of p53-responsive elements to expose their possible functional hierarchy. DNA-binding activity was assayed by electrophoretic retardation of the specific oligonucleotide upon interaction with extracts of cells expressing various p53 forms. Trans-activating properties of p53 were assessed by expression of the reporter CAT genes controlled by promoters carrying various p53-binding regions of DNA. Binding of p53 proved to vary among p53-responsive elements. Insertion of a p53-responsive element close to the minimal promoter makes it inducible by the wild-type p53. Noteworthily, the trans-activating capacity of DNA regions correlated with their binding to the wild-type p53. Although some mutant p53 forms preserved the ability to bind to p53-responsive elements, their trans-activation ability was lost.