Studies on the Role of C-Terminal Amino Acids in Mutant p53 Gain-of-Function and Poly(ADP-Ribose) Interaction

Author

• Valery Chavez, CUNY Graduate CenterFollow

Date of Degree

6-2026

Document Type

Doctoral Dissertation

Degree Name

Doctor of Philosophy

Program

Biology

Advisor

Jill Bargonetti

Committee Members

Andrew Wolfe

Benjamin Ortiz

Pablo Piexoto

Lydia Finley

Subject Categories

Biology | Cancer Biology | Cell Biology | Molecular Biology

Keywords

Mutant p53 (mtp53), Poly(ADP-ribose) (PAR), PARP1, Chromatin association, DNA replication, Triple-negative breast cancer (TNBC)

Abstract

Missense mutations in the TP53 gene generate stable mutant p53 (mtp53) proteins that accumulate on chromatin and acquire gain-of-function activities which promote tumor progression in Triple Negative Breast Cancer (TNBC). The p53 C-terminal domain (CTD) contains clusters of positively charged amino acids that support non-sequence-specific DNA binding, poly-ADP-ribose (PAR) interactions, and recruitment of replication-associated proteins, yet the contribution of individual CTD residues to mtp53 chromatin-based functions remains poorly defined. To interrogate the role of CTD charged residues known to be involved in interacting with PAR, hotspot mtp53 variants R273H and R248W were engineered with alanine substitutions at these five conserved amino acids (R363, K370, K372, R379, and K381) and examined alongside CTD deletion models in isogenic p53-null TNBC cells using chromatin fractionation, immunoprecipitation, proximity ligation assays, protein and transcript analyses, and proliferation assays. Alanine substitution of CTD charged residues reduced mtp53 chromatin association, diminished proximity to replicating DNA, PAR and reduced interaction with PARP1. CTD substitutions altered regulation of DNA replication associated proteins and the protein level in a mutant p53 context-dependent manner. Importantly, PARP PROTAC treatment depleted PARP1 and overall PARylation but did not disrupt mtp53 chromatin localization, indicating that the mtp53 C-terminus charge, rather than PARP1 abundance, facilitates chromatin association. Together, these findings identify specific positively charged amino acids in the p53 C-terminal domain as critical regulators of mutant p53 chromatin association and replication-linked oncogenic functions, establishing electrostatic control of the CTD as a central mechanism supporting mutant p53 activity in breast cancer.

Recommended Citation

Chavez, Valery, "Studies on the Role of C-Terminal Amino Acids in Mutant p53 Gain-of-Function and Poly(ADP-Ribose) Interaction" (2026). CUNY Academic Works.
https://academicworks.cuny.edu/gc_etds/6777