p53-regulated Transcriptional Program Associated with Genotoxic Stress-induced Apoptosis

Abstract

By using a genome-wide approach, we sought the identification of p53-regulated genes involved in cellular apoptosis. To this end, we assessed the transcriptional response of HCT116 colorectal cancer cells during apoptosis induced by the anticancer drug 5-fluorouracil as the function of p53 status, and we identified 230 potential targets that are regulated by p53. Previously identified p53 targets known to be involved in growth arrest and apoptosis were observed to be induced, thus validating the approach. Strikingly, we found that p53 regulates gene expression primarily through transcriptional repression (n ‫؍‬ 189) rather than activation (n ‫؍‬ 41), and selective blockade of p53-dependent gene repression resulted in the reduction in 5-fluorouracil-induced apoptosis. Reporter and chromatin immunoprecipitation assays demonstrated that p53 can suppress the promoter activities of three further studied candidate genes PLK, PTTG1, and CHEK1 but would only bind directly to PTTG1 and CHEK1 promoters, revealing that p53 can repress gene expression through both direct and indirect mechanisms. Moreover, RNA i -mediated knockdown of PLK and PTTG1 expression was sufficient to induce apoptosis, suggesting that repression of novel anti-apoptotic genes by p53 might contribute to a significant portion of the p53-dependent apoptosis. Our data support the divergent functions of p53 in regulating gene expression that play both synergistic and pleiotropic roles in p53-associated apoptosis.

The direct p53 target gene, FLJ11259/DRAM, is a member of a novel family of transmembrane proteins

“…4). Many genes are known to be regulated in a cell-specific and insult-specific manner [14,15], however the data here suggests that FLJ11259 is regulated in a p53-dependent manner in a variety of cell types and by at least two distinct DNA damaging agents, cisplatin and as previously shown, etoposide [6]. This supports a potential role for FLJ11259 in the biological response of tumors to chemotherapeutic agents.…”

CYFIP2, a Direct p53 Target, is Leptomycin-B Sensitive

“…These results are consistent with those from previously published microarray studies. 11,24,25 Saller et al first identified CYFIP2 (also known as PIR121) as a candidate p53 target gene whose mRNA was up regulated 5.3X by wild-type p53, 15.3X by a pro-apoptotic p53-121F mutant, and not induced in response to an anti-apoptotic p53-277R mutant, respectively, when stably expressed under TET control in H1299 cells or adenovirally expressed in Saos-2 (null for p53) or U2OS (expressing WT p53) cells. Using the nucleotide analog 5-fluorouracil, a DNA damage inducing chemotherapeutic drug, Kho et al detected a 2X increase in CYFIP2 mRNA by microarray in HCT116 cells in a p53-dependent manner, suggesting that CYFIP2 can be induced by endogenous p53.…”

A p53-dominant transcriptional response to cisplatin in testicular germ cell tumor-derived human embyronal carcinoma

“…The identity and associated function of each gene is provided in Table 1. Notably, 25 of the 46 induced genes have previously been identified as p53 target genes (Kannan et al, 2001;Sax and El-Deiry, 2003;Kho et al, 2004) (bold in Table 1), including nine of the top 10 genes ranked according to fold-change. The exception is the hypothetical protein FLJ11259, which is a potential novel p53 target.…”

“…(2) Indicates evidence for p53 target gene based on previous p53-specific microarray (Kannan et al, 2001;Sax and El-Diery, 2003;Kho et al, 2004). (NA) Indicates the information concerning a p53 target is not available.…”