Most mutant p53 proteins are not able to achieve a conformation that is capable of DNA binding despite extended chaperone interactions. Presentation of p53 for ubiquitylation by MDM2, and possibly CHIP, is also impaired, which leads to the accumulation of aggregation-prone, dysfunctional protein. The binding of geldanamycin (GA) to HSP90 inhibits normal chaperone cycling and drives the degradation of p53 mutants, which leads to a decrease in their cellular levels. It remains unclear whether this decrease is sufficient to disrupt the dominant-negative and positive tumour-promoting activities of such mutants.