title: 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.
authors.affiliation: Laboratory of Molecular Pharmacology, and Cell and Medical Biology, Genome Institute of Singapore, Genome Building 02-01, 60 Biopolis Street, Singapore 138672.
authors.forename: Patricia S
authors.initials: PS
authors.lastname: Kho
authors.forename: Zhen
authors.initials: Z
authors.lastname: Wang
authors.forename: Li
authors.initials: L
authors.lastname: Zhuang
authors.forename: Yuqing
authors.initials: Y
authors.lastname: Li
authors.forename: Joon-Lin
authors.initials: JL
authors.lastname: Chew
authors.forename: Huck-Hui
authors.initials: HH
authors.lastname: Ng
authors.forename: Edison T
authors.initials: ET
authors.lastname: Liu
authors.forename: Qiang
authors.initials: Q
authors.lastname: Yu
mesh_terms: D017209:Apoptosis / Q000187:drug effects / Q000235:genetics*; D001483:Base Sequence; D045744:Cell Line, Tumor; D000071877:Checkpoint Kinase 1; D064447:Checkpoint Kinase 2; D003110:Colonic Neoplasms / Q000235:genetics; D003513:Cycloheximide / Q000494:pharmacology; D017931:DNA Primers; D005472:Fluorouracil / Q000633:toxicity; D015972:Gene Expression Regulation, Neoplastic / Q000187:drug effects / Q000235:genetics; D015894:Genome, Human; D006801:Humans; D020411:Oligonucleotide Array Sequence Analysis; D011401:Promoter Regions, Genetic; D011494:Protein Kinases / Q000235:genetics; D017346:Protein Serine-Threonine Kinases / Q000235:genetics; D034741:RNA, Small Interfering / Q000235:genetics; D020133:Reverse Transcriptase Polymerase Chain Reaction; D013312:Stress, Physiological; D014158:Transcription, Genetic / Q000187:drug effects / Q000235:genetics*; D014162:Transfection; D016159:Tumor Suppressor Protein p53 / Q000378:metabolism*
chemical_list: D017931:DNA Primers; D034741:RNA, Small Interfering; D016159:Tumor Suppressor Protein p53; D003513:Cycloheximide; D011494:Protein Kinases; D064447:Checkpoint Kinase 2; C000605867:CHEK1 protein, human; C578634:CHEK2 protein, human; D000071877:Checkpoint Kinase 1; D017346:Protein Serine-Threonine Kinases; D005472:Fluorouracil