triphosphate nucleotidohydrolase (dUTPase) catalyzes the hydrolysis of dUTP to dUMP and PPi. tumor suppressor p53. Launch Deoxyuridine triphosphate nucleotidohydrolase (dUTPase) may be the exclusive enzyme in charge of the hydrolysis of dUTP to dUMP and pyrophosphate concurrently offering substrate for thymidylate MPEP HCl synthase (TS) and getting rid of dUTP in the DNA biosynthetic pathway. Although dUTP is certainly a standard intermediate in DNA synthesis its comprehensive deposition and misincorporation into DNA is certainly lethal both in prokaryotic and eukaryotic organisms as evidenced from knockout models (1 2 Rabbit Polyclonal to Smad1. Importantly uracil misincorporation also represents a major mechanism of cytotoxicity induced by the TS-inhibitor class of chemotherapeutic brokers including the fluoropyrimidines 5-fluorouracil (5-FU) fluorodeoxyuridine (FUdR) and capecitabine which are broadly used in the treatment of cancers of the gastrointestinal tract breast and head and neck (3). Inhibition of TS induces a metabolic blockade depleting thymidylate pools and in some instances promoting the accumulation of intracellular dUTP pools and subsequent misincorporation of uracil into DNA resulting in DNA damage and cell death (4 5 Expression of dUTPase is usually reported to be an important mediator of MPEP HCl resistance to therapeutic brokers that target TS both and gene reveals putative regulatory motifs including potential binding sites for NF-κB E2F and Sp1 transcription factors (15). Recently a genome-wide ChIP-on-chip identified dUTPase in a subset of 127 genes bound by MPEP HCl E2F family members (18). Despite the presence of these putative S-phase-specific binding sites in the DUT-N promoter region functional analysis of this gene has not been previously reported. Several studies have also reported downregulation of dUTPase during apoptosis (19 20 and that dUTPase expression may be modulated by the tumor suppressor gene p53 (21 22 In response to stress stimuli such as DNA damage p53 can initiate cell cycle arrest through transcriptional induction of cell cycle inhibitors such as p21cip1/waf1 mediate DNA repair or induce apoptotic cell death. These mechanisms are designed to prevent proliferation of cells made up of damaged DNA and reduce the likelihood of MPEP HCl tumor formation. Interestingly mutations in p53 are one of the most common genetic aberrations detected in malignant disease with >50% of colon tumors exhibiting mutation (23). In prostate cancer cells dUTPase was one of many genes identified by microarray analysis as significantly repressed following introduction of wild-type p53 (22). In MCF-7 (p53 wild-type) breast cancer cells microarray analysis also identified dUTPase mRNA within an extensive panel of genes repressed following 5-FU treatment (21). However the precise mechanism of the downregulation of dUTPase has not been determined and it is unknown as to whether this phenomenon is the result of indirect downstream events induced by p53 itself or its transactivation and repressive gene targets. Furthermore dUTPase was one of a number of genes identified as upregulated in p53-null mouse embryonic fibroblasts following introduction of the human tumor-derived p53 R175H by subtraction hybridization (24). As dUTPase is an essential enzyme in maintaining genomic stability and demonstrates both aberrant intratumoral expression and an association with resistance to 5-FU we sought to perform the first functional characterization of the promoter and elucidate the mechanisms involved in regulating dUTPase expression. In addition p53 mutations are widely observed in many cancers and as the fluoropyrimidines remain the mainstay..