title: SN2 DNA-alkylating agent-induced phosphorylation of p53 and activation of p21 gene expression.
abstract: p53 is an important player in the cellular response to genotoxic stress whose functions are regulated by phosphorylation of a number of serine and threonine residues. Phosphorylation of p53 influences its DNA-binding and gene regulation activities. This study examines p53 phosphorylation in HCT-116 (MMR-deficient) and HCT-116+ch3 (MMR-proficient) human colon cancer cells treated with a S(N)2 DNA-alkylating agent, methylmethane sulfonate (MMS). MMS induces phosphorylation of p53 on Ser15 and Ser392 in a dose- and time-dependent manner. MMS-induced p53 phosphorylation is independent of DNA mismatch repair (MMR) activity. Nuclear extracts from MMS-treated HCT-116 cells had higher p21WAF1/Cip1 (p21) promoter DNA-binding activity in vitro opposed to untreated cells. After MMS treatment, the activation of the cloned p21 promoter in a transient transfection assay and endogenous p21 mRNA levels in HCT-116(p53+/+) versus HCT-116(p53-/-) cells increased, which correlates with an increased levels of phospho-p53(Ser15) and phospho-p53(Ser392). These results suggest that SN2 DNA-alkylating agent-induced phosphorylation of p53 on Ser15 and Ser392 increases its DNA-binding properties to cause an increased expression of p21 that may play a role in cell cycle arrest and/or apoptosis of HCT-116 cells.
authors.affiliation: Department of Anatomy and Cell Biology, UF Shands Cancer Center, College of Medicine, University of Florida, P.O. Box 100232, Gainesville, FL 32610, USA.
authors.forename: Aruna S
authors.initials: AS
authors.lastname: Jaiswal
authors.forename: Satya
authors.initials: S
authors.lastname: Narayan
mesh_terms: D018906:Antineoplastic Agents, Alkylating / Q000633:toxicity*; D002467:Cell Nucleus / Q000187:drug effects / Q000378:metabolism; D003110:Colonic Neoplasms; D050759:Cyclin-Dependent Kinase Inhibitor p21; D016213:Cyclins / Q000235:genetics*; D015972:Gene Expression Regulation, Neoplastic / Q000187:drug effects*; D016158:Genes, p53; D006801:Humans; D008741:Methyl Methanesulfonate / Q000633:toxicity*; D010766:Phosphorylation; D010768:Phosphoserine / Q000378:metabolism; D011401:Promoter Regions, Genetic; D014158:Transcription, Genetic / Q000187:drug effects; D014162:Transfection; D014407:Tumor Cells, Cultured; D016159:Tumor Suppressor Protein p53 / Q000378:metabolism*
chemical_list: D018906:Antineoplastic Agents, Alkylating; C493956:CDKN1A protein, human; D050759:Cyclin-Dependent Kinase Inhibitor p21; D016213:Cyclins; D016159:Tumor Suppressor Protein p53; D010768:Phosphoserine; D008741:Methyl Methanesulfonate