A divergent synthetic strategy for generating helical p53 peptides bearing functionalised staple linkages, allowing for efficient optimisation of cellular activity.

No abstract

These results demonstrate that a p16-derived peptide can mediate three of the known functions of p16: firstly, it interacts with cdk4 and cdk6; secondly, it inhibits pRb phosphorylation in vitro and in vivo; and thirdly, it blocks entry into S phase. The fact that one small synthetic peptide can enter the cells directly from the tissue culture medium to inhibit pRb phosphorylation and block cell-cycle progression makes this an attractive approach for future peptidometic drug design. Our results suggest a novel and exciting means by which the function of the p16 suppressor gene can be restored in human tumours.

An extensive series of histological sections reflecting the various states of normal breast tissue, and a range of benign and malignant lesions, were examined for the expression of the p53 protein using a panel of anti-p53 antibodies. In 2 separate series the results of using frozen or methacarn-fixed, paraffin-embedded sections were compared. Strong positive staining for p53 was detected in over 50% of the malignant lesions when frozen sections were used. This number fell to just over 20% when methacarn-fixed sections were examined. In neither series was any p53 staining seen in normal breast or in the benign lesions. Studies by Western blotting on breast cell lines confirmed that this histological signal is due to a pronounced over-expression of the p53 protein. Earlier studies show that this over-expression is associated with mutation of the p53 gene. Mutation of the p53 gene with over-expression of the mutant protein is therefore one of the most frequent specific genetic changes in malignant breast cancer.

Targeted degradation approaches such as proteolysis targeting chimeras (PROTACs) offer new ways to address disease through tackling challenging targets and with greater potency, efficacy, and specificity over traditional approaches. However, identification of high-affinity ligands to serve as PROTAC starting points remains challenging. As a complementary approach, we describe a class of molecules termed biological PROTACs (bioPROTACs)—engineered intracellular proteins consisting of a target-binding domain directly fused to an E3 ubiquitin ligase. Using GFP-tagged proteins as model substrates, we show that there is considerable flexibility in both the choice of substrate binders (binding positions, scaffold-class) and the E3 ligases. We then identified a highly effective bioPROTAC against an oncology target, proliferating cell nuclear antigen (PCNA) to elicit rapid and robust PCNA degradation and associated effects on DNA synthesis and cell cycle progression. Overall, bioPROTACs are powerful tools for interrogating degradation approaches, target biology, and potentially for making therapeutic impacts.