Unraveling the Function of J-domain Proteins in p53 Stabilization

Proteins are constantly at risk of misfolding, which not only prevents them from functioning properly, but can also cause them to aggregate and form potentially cytotoxic, insoluble complexes. Chaperones are crucial protein quality control components that maintain proteins’ native conformation, refold misfolded proteins, and can even break apart and solubilize protein aggregates. In cancer cells, chaperones are often overexpressed, which enhances protein folding capabilities and anti-apoptotic traits. Accordingly, tumor cells which overexpress Hsp70 are correlated with poor prognosis. One important target of the Hsp70 system in tumor cells are mutated p53 proteins, whose presence strongly correlates with cancer cell survival.

We studied the structure and dynamic properties of the Hsp70 chaperone system, with emphasis on interaction and remodeling of their substrates, such as WT and mutant p53 proteins. The Hsp70 system heavily relies on J-domain proteins (JDPs) for client selection and delivery, as well as Hsp70 activation. JDPs are a diverse family of proteins containing two distinct classes, class-A (DnaJA) and class-B (DnaJB), each with several members. Little, however, is known regarding the selectivity of the different JDP classes and their function in p53 stabilization.

Using biochemical assays and NMR spectroscopy, we have characterized the interaction and remodeling performed by different JDP proteins on destabilizing p53 mutants. Our results show that DnaJAs inhibit aggregation of p53 mutants by directly binding to their aggregation prone region and preventing them from further misfolding. Our findings mark DnaJAs as a new target for developing novel therapeutic approaches for cancer treatment.