NAD⁺ Modulates p53 DNA Binding Specificity and Function

Abstract

DNA damage induces p53 DNA binding activity, which affects tumorigenesis, tumor responses to therapies, and the toxicities of cancer therapies (B. Vogelstein, D. Lane, and A. J. Levine, Nature 408:307-310, 2000; K. H. Vousden and X. Lu, Nat. Rev. Cancer 2:594-604, 2002). Both transcriptional and transcription-independent activities of p53 contribute to DNA damage-induced cell cycle arrest, apoptosis, and aneuploidy prevention (M. B. Kastan et al., Cell 71:587-597, 1992; K. H. Vousden and X. Lu, Nat. Rev. Cancer 2:594-604, 2002). Small-molecule manipulation of p53 DNA binding activity has been an elusive goal, but here we show that NAD⁺ binds to p53 tetramers, induces a conformational change, and modulates p53 DNA binding specificity in vitro. Niacinamide (vitamin B₃) increases the rate of intracellular NAD⁺ synthesis, alters radiation-induced p53 DNA binding specificity, and modulates activation of a subset of p53 transcriptional targets. These effects are likely due to a direct effect of NAD⁺ on p53, as a molecule structurally related to part of NAD⁺, TDP, also inhibits p53 DNA binding, and the TDP precursor, thiamine (vitamin B₁), inhibits intracellular p53 activity. Niacinamide and thiamine affect two p53-regulated cellular responses to ionizing radiation: rereplication and apoptosis. Thus, niacinamide and thiamine form a novel basis for the development of small molecules that affect p53 function in vivo, and these results suggest that changes in cellular energy metabolism may regulate p53.

We thank Mary Relling, Jean Cai, and Yi Su (Pharmaceutical Sciences, St. Jude Children's Research Hospital) for HPLC analysis of NAD⁺, Vincent Kidd and Susan Ragsdale (Cancer Core Cytogenetics Laboratory, St. Jude Children's Research Hospital) for analysis of mitotic spread chromosome content, and Gerald Zambetti (Biochemistry, St. Jude Children's Research Hospital) for helpful comments after reading the manuscript.

This work was supported by grants from the NIH (ES05777 and CA21765) and by the American Lebanese Syrian Associated Charities of the St. Jude Children's Research Hospital.