ACTIVATION OF THE HUMAN-IMMUNODEFICIENCY-VIRUS TYPE-1 LONG TERMINAL REPEAT BY TRANSFORMING MUTANTS OF HUMAN P53

We have studied the effects of human wild-type and mutant p53s on the long terminal repeat (LTR) promoter of human immunodeficiency virus ty pe 1 (HIV) HeLa cells were cotransfected with a wild-type or mutant p5 3 expression plasmid and a plasmid containing a chloramphenicol acetyl transferase reporter gene under HIV LTR promoter control. As expected, expression of wild-type p53 inhibited promoter function. Expression o f a p53 mutated at any one of the four amino acid positions 175, 248, 273, and 281 correlated with a significant increase of the HIV promote r activity. The HIV LTR was also significantly activated in Saos-2 cel ls that do not express endogenous p53. This finding suggests a gain-of -transactivation function by mutation of the p53 gene. Cotransfection of wild-type and mutant p53-281G expression plasmids indicated that ei ther the wild type or the mutant was dominant in inhibiting or enhanci ng promoter activity, respectively, when transfected in excess of the other. Transfection experiments showed transactivation even when the S p1, NF-kappa B, and TATA sites in the LTR were individually mutated. S ynthetic minimal promoter constructs containing two Sp1 sites or two N F-kappa B sites or an ATF site are also significantly activated by the mutant p53-281G. Thus, the mutant protein may activate transcription through interaction with either a general transcription factor or a co mmon factor that bridges the basal transcription machinery and the tra nscription factors Sp1, NF-kappa B, and ATF.