The C-terminus of Gain-of-Function Mutant p53 R273H Is Required for Association with PARP1 and Poly-ADP-Ribose.

Unlabelled: The TP53 gene is mutated in 80% of triple-negative breast cancers. Cells that harbor the hot-spot p53 gene mutation R273H produce an oncogenic mutant p53 (mtp53) that enhances cell proliferative and metastatic properties. The enhanced activities of mtp53 are collectively referred to as gain-of-function (GOF), and may include transcription-independent chromatin-based activities shared with wild-type p53 (wtp53) such as association with replicating DNA and DNA replication associated proteins like PARP1.

Oligomerization of Mutant p53 R273H is not Required for Gain-of-Function Chromatin Associated Activities.

The gene is often mutated in cancer, with missense mutations found in the central DNA binding domain, and less often in the C-terminal oligomerization domain (OD). These types of mutations are found in patients with the rare inherited cancer predisposition disorder called Li-Fraumeni syndrome. We previously found that mutant p53 (mtp53) R273H associates with replicating DNA and promotes the chromatin association of replication-associated proteins mini-chromosome maintenance 2 (MCM2), and poly ADP-ribose polymerase 1(PARP1).

Frame-shift mediated reduction of gain-of-function p53 R273H and deletion of the R273H C-terminus in breast cancer cells result in replication-stress sensitivity.

We recently documented that gain-of-function (GOF) mutant p53 (mtp53) R273H in triple negative breast cancer (TNBC) cells interacts with replicating DNA and PARP1. The missense R273H GOF mtp53 has a mutated central DNA binding domain that renders it unable to bind specifically to DNA, but maintains the capacity to interact tightly with chromatin. Both the C-terminal domain (CTD) and oligomerization domain (OD) of GOF mtp53 proteins are intact and it is unclear whether these regions of mtp53 are responsible for chromatin-based DNA replication activities.

Targeting Triple Negative Breast Cancer with a Nucleus-Directed p53 Tetramerization Domain Peptide.

Triple negative breast cancer (TNBC) has no targeted detection or treatment method. Mutant p53 (mtp53) is overexpressed in >80% of TNBCs, and the stability of mtp53 compared to the instability of wild-type p53 (wtp53) in normal cells makes mtp53 a promising TNBC target for diagnostic and theranostic imaging. We generated Cy5p53Tet, a novel nucleus-penetrating mtp53-oligomerization-domain peptide (mtp53ODP) to the tetramerization domain (TD) of mtp53.

Gain-of-Function Mutant p53 R273H Interacts with Replicating DNA and PARP1 in Breast Cancer.

Over 80% of triple-negative breast cancers (TNBC) express mutant p53 (mtp53) and some contain oncogenic gain-of-function (GOF) p53. We previously reported that GOF mtp53 R273H upregulates the chromatin association of mini chromosome maintenance (MCM) proteins MCM2-7 and PARP and named this the mtp53-PARP-MCM axis. In this study, we dissected the function and association between mtp53 and PARP using a number of different cell lines, patient-derived xenografts (PDX), tissue microarrays (TMA), and The Cancer Genome Atlas (TCGA) database.