Designer polyQ fusion proteins sequester USP7/HDM2 for modulating P53 functionality

Overexpression of USP7 and HDM2 inactivates P53 signaling in tumor cells and facilitates their progression, but suppression of these targets by conventional strategies to reactivate P53 function remains a challenge. We applied polyQ sequences and target-interacting peptides to engineer polyQ fusion proteins that specifically sequester the targets, hence depleting their availabilities and modulating the P53 functionality. We have revealed that the designer fusion Atx7_93Q-N172-IRF (IRF sequence: SPGEGPSGTG) sequesters USP7 and/or HDM2 into aggregates and thereby increases the P53 level, but it depends on the IRF repeats fused, suggesting that depletion of the USP7 availability plays a dual role in controlling P53 stability. Direct sequestration of HDM2 by Atx7_93Q-N172-PMI (PMI: TSFAEYWNLLSP) remarkably reduces the protein level of soluble HDM2 and hence increases the P53 level, which consequently up-regulates expression of the downstream genes. The polyQ-fusion strategy is feasible to modulate the P53 stability and functionality, furnishing a therapeutic potential for cancers.