Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: EC:2.3.1.28 (chloramphenicol acetyltransferase)
 5,100 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Previous analysis of the human cytomegalovirus (HCMV) DNA polymerase (UL54) early gene promoter demonstrated that transcriptional activation of this gene is dependent upon the interaction of cellular transcription factors with viral transactivators (J. A. Kerry, M. A. Priddy, T. Y. Jervey, C. P. Kohler, T. L. Staley, C. D. Vanson, T. R. Jones, A. C. Iskenderian, D. G. Anders, and R. M. Stenberg, J. Virol. 70:373-382, 1996). A sequence element, IR1, was shown to be the primary regulatory element of this promoter in transient assays. However, assessment of this element in the context of the viral genome revealed IR1-independent activation at late times after infection. To extend these studies, we aim to identify additional sequence elements involved in the activation of the UL54 promoter. Our present studies demonstrate that the level of binding of proteins to the ATF site in the UL54 promoter is enhanced by viral infection. Furthermore this increase is sensitive to treatment with phosphonoacetic acid (PAA), a DNA synthesis inhibitor. These data suggest that the increase in the level of ATF binding activity is regulated, either directly or indirectly, by HCMV late gene expression. By using specific antibodies, we determined that ATF-1 was a major component of the proteins binding to the UL54 ATF site at late times. In addition, we have demonstrated direct binding of recombinant ATF-1 to the UL54 ATF site. To assess the biological significance of these events, a recombinant virus construct was generated that contained the UL54 promoter with a mutation in the ATF site regulating expression of the chloramphenicol acetyltransferase (CAT) reporter gene inserted between open reading frames US9 and US10. Analysis of this virus (RVATFmCAT) revealed that mutation of the ATF site does not alter the kinetics of UL54 promoter activation. However, levels of CAT mRNA and activity were reduced by 5- to 10-fold compared to those of the wild-type promoter at all stages of infection. These findings indicate that ATF-1 can regulate the levels of UL54 promoter activity at both early and late times. Furthermore, these results imply that HCMV can regulate the activity of cellular factors involved in early gene regulation.
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PMID:The role of ATF in regulating the human cytomegalovirus DNA polymerase (UL54) promoter during viral infection. 903 45

Thymidine dinucleotide (pTpT) stimulates melanogenesis in mammalian pigment cells and intact skin, mimicking the effects of UV irradiation and UV-mimetic DNA damage. Here it is shown that, in addition to tanning, pTpT induces a second photoprotective response, enhanced repair of UV-induced DNA damage. This enhanced repair results in a 2-fold increase in expression of a UV-damaged chloramphenicol acetyltransferase expression vector transfected into pTpT-treated skin fibroblasts and keratinocytes, compared with diluent-treated cells. Direct measurement of thymine dimers and (6-4) photoproducts by immunoassay demonstrates faster repair of both of these UV-induced photoproducts in pTpT-treated fibroblasts. This enhanced repair capacity also improves cell survival and colony-forming ability after irradiation. These effects of pTpT are accomplished, at least in part, by the up-regulation of a set of genes involved in DNA repair (ERCC3 and GADD45) and cell cycle inhibition (SDI1). At least two of these genes (GADD45 and SDI1) are known to be transcriptionally regulated by the p53 tumor suppressor protein. Here we show that pTpT activates p53, leading to nuclear accumulation of this protein, and also increases the specific binding of this transcription factor to its DNA consensus sequence.
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PMID:Enhancement of DNA repair in human skin cells by thymidine dinucleotides: evidence for a p53-mediated mammalian SOS response. 935

We have recently reported that the geranylgeranyltransferase I inhibitor GGTI-298 arrests human tumor cells at the G1 phase of the cell cycle and increases the protein and RNA levels of the cyclin-dependent kinase inhibitor p21(WAF1/CIP1). Here, we show that GGTI-298 acts at the transcriptional level to induce p21(WAF1/CIP1) in a human pancreatic carcinoma cell line, Panc-1. This upregulation of p21(WAF1/CIP1) promoter was selective, since GGTI-298 inhibited serum responsive element- and E2F-mediated transcription. A functional analysis of the p21(WAF1/CIP1) promoter showed that a GC-rich region located between positions -83 and -74, which contains a transforming growth factor beta-responsive element and one Sp1-binding site, is sufficient for the upregulation of p21(WAF1/CIP1) promoter by GGTI-298. Electrophoretic mobility shift assays showed a small increase in the amount of DNA-bound Sp1-Sp3 complexes. Furthermore, the analysis of Sp1 transcriptional activity in GGTI-298-treated cells by using GAL4-Sp1 chimera or Sp1-chloramphenicol acetyltransferase reporter revealed a significant increase in Sp1-mediated transcription. Moreover, GGTI-298 treatment also resulted in increased Sp1 and Sp3 phosphorylation. These results suggest that GGTI-298-mediated upregulation of p21(WAF1/CIP1) involves both an increase in the amount of DNA-bound Sp1-Sp3 and enhancement of Sp1 transcriptional activity. To identify the geranylgeranylated protein(s) involved in p21(WAF1/CIP1) transcriptional activation, we analyzed the effects of the small GTPases Rac1 and RhoA on p21(WAF1/CIP1) promoter activity. The dominant negative mutant of RhoA, but not Rac1, was able to activate p21(WAF1/CIP1). In contrast, constitutively active RhoA repressed p21(WAF1/CIP1). Accordingly, the ADP-ribosyl transferase C3, which specifically inhibits Rho proteins, enhanced the activity of p21(WAF1/CIP1). Taken together, these results suggest that one mechanism by which GGTI-298 upregulates p21(WAF1/CIP1) transcription is by preventing the small GTPase RhoA from repressing p21(WAF1/CIP1) induction.
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PMID:p21(WAF1/CIP1) is upregulated by the geranylgeranyltransferase I inhibitor GGTI-298 through a transforming growth factor beta- and Sp1-responsive element: involvement of the small GTPase rhoA. 981 84

The proliferating cell nuclear antigen (PCNA) is a highly conserved cellular protein that functions both in DNA replication and in DNA repair. Exposure of a rat embryo fibroblast cell line (CREF cells) to gamma radiation induced simultaneous expression of PCNA with the p53 tumor suppressor protein and the cyclin-dependent kinase inhibitor p21(WAF1/Cip1). PCNA mRNA levels transiently increased in serum-starved cells exposed to ionizing radiation, an observation suggesting that the radiation-associated increase in PCNA expression could be dissociated from cell cycle progression. Irradiation of CREF cells activated a transiently expressed PCNA promoter chloramphenicol acetyltransferase construct through p53 binding sequences via a mechanism blocked by a dominant negative mutant p53. Electrophoretic mobility shift assays with nuclear extracts prepared from irradiated CREF cells produced four p53-specific DNA-protein complexes with the PCNA p53 binding site. Addition of monoclonal antibody PAb421 (p53-specific) or AC238 (specific to the transcriptional coactivator p300/CREB binding protein) to the mobility shift assay distinguished different forms of p53 that changed in relative abundance with time after irradiation. These findings suggest a complex cellular response to DNA damage in which p53 transiently activates expression of PCNA for the purpose of limited DNA repair. In a population of nongrowing cells with diminished PCNA levels, this pathway may be crucial to survival following DNA damage.
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PMID:p53-mediated regulation of proliferating cell nuclear antigen expression in cells exposed to ionizing radiation. 985 27