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)

p53 is a nuclear phosphoprotein whose function is classified as tumor suppression. Studies have shown that p53 functions by binding to p53 DNA recognition sequences and regulates transcription of growth-regulatory genes. Various p53 recognition sequences have recently been identified. pOST2 contained two copies of a palindromic high-affinity DNA-binding sequence for p53; the other p53 recognition sequences included p53-binding fragments found in the human ribosomal gene cluster (pRGC) region and in the murine muscle creatine kinase promoter (pMCK). The purpose of this study was to compare the abilities of various p53 recognition sequences to mediate transcription in the presence of endogenously produced wild-type (wt) or mutant p53. Three p53-responsive chloramphenicol acetyltransferase (CAT) reporter constructs (pOST2, pRGC, and pMCK) that contain one or two copies of p53 recognition sequences upstream of a herpes thymidine kinase (TK) promoter and CAT reporter cDNA were constructed. Either a p53-responsive gene or a control reporter gene was transfected into human carcinoma cell lines (having various p53 mutations) either with or without a wt or mutant p53 expression vector. CAT activity was assayed to measure transactivation through the various p53-responsive elements. We showed that pOST2 had a greater ability to mediate transactivation by p53 than either pRGC or pMCK. p53 with a mutation at either codon 175 or 248 was unable to transactivate a reporter gene with pOST2, pRGC, or pMCK. We found it interesting that pOST2, but not pRGC or pMCK, was able to mediate transactivation in cell lines that produce codon 273-mutant p53. These findings suggest that various sensitivities of the different p53-responsive elements to specific mutant and wt p53s may be an important factor in the role of p53 as a transcriptional activator both under normal physiological conditions and during carcinogenesis.
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PMID:p53 transactivation through various p53-responsive elements. 864 24

Chicken NF-M transcription factor, in cooperation with either c-Myb or v-Myb, is active in the combinatorial activation of myeloid-cell-specific genes in heterologous cell types, such as embryonic fibroblasts. In humans, similar effects were observed with homologous members of the CCAAT/enhancer-binding protein (C/EBP) family of transcriptional regulators, especially the human homolog of chicken NF-M, C/EBP-beta (NF-IL6). However, the NF-IL6 gene is expressed in a variety of nonmyeloid cell types and is strongly inducible in response to inflammatory stimuli, making it an unlikely candidate to have an exclusive role as a combinatorial differentiation switch during myelopoiesis in human cells. By using a reverse transcription-PCR-based approach and a set of primers specific for the DNA-binding domains of highly homologous members of the C/EBP family of transcriptional regulators, we have cloned a novel human gene encoding a member of the C/EBP gene family, identified as the human homolog of CRP1, C/EBP-epsilon. A 1.2-kb cDNA encoding full-length human C/EBP-epsilon was cloned from a promyelocyte-late myeloblast-derived lambda gt11 library. Molecular analysis of the cDNA and genomic clones indicated the presence of two exons encoding a protein with an apparent molecular mass of 32 kDa and a pI of 9.5. Primer extension analysis of C/EBP-epsilon mRNA detected a single major transcription start site approximately 200 bp upstream of the start codon. The putative promoter area is similar to those of several other myeloid-cell-specific genes in that it contains no TATAAA box but has a number of purine-rich stretches with multiple sites for the factors of the Ets family of transcriptional regulators. Northern blot analyses indicated a highly restricted mRNA expression pattern, with the strongest expression occurring in promyelocyte and late-myeloblast-like cell lines. Western blot and immunoprecipitation studies using rabbit anti-C/EBP-epsilon antibodies raised against the N-terminal portion of C/EBP-epsilon (amino acids 1 to 115) showed that C/EBP-epsilon is a 32-kDa nuclear phosphoprotein. The human C/EBP-epsilon protein exhibited strong and specific binding to double-stranded DNA containing consensus C/EBP sites. Cotransfection of the C/EBP-epsilon sense and antisense expression constructs together with chloramphenicol acetyltransferase reporter vectors containing myeloid-cell-specific c-mim and human myeloperoxidase promoters suggested a role for C/EBP-epsilon transcription factor in the regulation of a subset of myeloid-cell-specific genes. Transient tranfection of a promyelocyte cell line (NB4) with a C/EBP-epsilon expression plasmid increased cell growth by sevenfold, while antisense C/EBP-epsilon caused a fivefold decrease in clonal growth of these cells.
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PMID:Cloning of the novel human myeloid-cell-specific C/EBP-epsilon transcription factor. 903 64

The product of the retinoblastoma susceptibility gene, pRB, is a nuclear phosphoprotein that controls cell growth by binding to and suppressing the activities of transcription factors such as the E2F family. Transactivation activity is inhibited when E2F is bound to hypophosphorylated pRB and released when pRB is phosphorylated by cyclin-dependent kinases (CDKs). To determine which of 16 potential CDK phosphorylation sites regulated the pRB-E2F interaction, mutant pRB proteins produced by site-directed mutagenesis were tested for the ability to suppress E2F-mediated transcription in a reporter chloramphenicol acetyltransferase assay. Surprisingly, no one CDK site regulated the interaction of pRB with E2F when E2F was bound to DNA. Instead, disruption of transcriptional repression resulted from accumulation of phosphate groups on the RB molecule.
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PMID:Cumulative effect of phosphorylation of pRB on regulation of E2F activity. 1020 50