by
Matthew Jennis;
Che-Pei Kung;
Subhasree Basu;
Anna Budina-Kolomets;
Julia I-Ju Leu;
Sakina Khaku;
Jeremy P. Scott;
Kathy Q. Cai;
Michelle R. Campbell;
Devin K. Porter;
Xuting Wang;
Douglas A. Bell;
Xiaoxian Li;
David S. Garlick;
Qin Liu;
Monica Hollstein;
Donna L. George;
Maureen E. Murphy
A nonsynonymous single-nucleotide polymorphism at codon 47 in TP53 exists in African-descent populations (P47S, rs1800371; referred to here as S47). Here we report that, in human cell lines and a mouse model, the S47 variant exhibits a modest decrease in apoptosis in response to most genotoxic stresses compared with wild-type p53 but exhibits a significant defect in cell death induced by cisplatin. We show that, compared with wild-type p53, S47 has nearly indistinguishable transcriptional function but shows impaired ability to transactivate a subset of p53 target genes, including two involved in metabolism: Gls2 (glutaminase 2) and Sco2. We also show that human and mouse cells expressing the S47 variant are markedly resistant to cell death by agents that induce ferroptosis (iron-mediated nonapoptotic cell death). We show that mice expressing S47 in homozygous or heterozygous form are susceptible to spontaneous cancers of diverse histological types. Our data suggest that the S47 variant may contribute to increased cancer risk in individuals of African descent, and our findings highlight the need to assess the contribution of this variant to cancer risk in these populations. These data also confirm the potential relevance of metabolism and ferroptosis to tumor suppression by p53.
The multidomain zinc finger (ZnF) protein PRDM9 (PRD1–BF1–RIZ1 homologous domain-containing 9) is thought to influence the locations of recombination hot spots during meiosis by sequence-specific DNA binding and trimethylation of histone H3 Lys4. The most common variant of human PRDM9, allele A (hPRDM9A), recognizes the consensus sequence 5′-NCCNCCNTNNCCNCN-3′. We cocrystallized ZnF8–12 of hPRDM9A with an oligonucleotide representing a known hot spot sequence and report the structure here. ZnF12 was not visible, but ZnF8–11, like other ZnF arrays, follows the right-handed twist of the DNA, with the α helices occupying the major groove. Each α helix makes hydrogen-bond (H-bond) contacts with up to four adjacent bases, most of which are purines of the complementary DNA strand. The consensus C:G base pairs H-bond with conserved His or Arg residues in ZnF8, ZnF9, and ZnF11, and the consensus T:A base pair H-bonds with an Asn that replaces His in ZnF10. Most of the variable base pairs (N) also engage in H bonds with the protein. These interactions appear to compensate to some extent for changes from the consensus sequence, implying an adaptability of PRDM9 to sequence variations. We investigated the binding of various alleles of hPRDM9 to different hot spot sequences. Allele C was found to bind a C-specific hot spot with higher affinity than allele A bound A-specific hot spots, perhaps explaining why the former is dominant in A/C heterozygotes. Allele L13 displayed higher affinity for several A-specific sequences, allele L9/L24 displayed lower affinity, and allele L20 displayed an altered sequence preference. These differences can be rationalized structurally and might contribute to the variation observed in the locations and activities of meiotic recombination hot spots.