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

We have isolated a genomic clone containing the mouse neu gene. The 5' end of the mouse neu gene was localized by Southern analysis, subcloned and characterized. DNA sequence analysis revealed that the promoter region is 67% G+C-rich and lacks a TATA box, although a CAAT box is present. By sequence comparison, we identified several consensus recognition sequences for general transcription factors such as Sp1, E4TF1, AP2, OTF-1 and GCF, as well as recognition sequences for RVF, E1A and GTG, which have recently been identified in the rat neu promoter. Functional promoter activity was demonstrated by the ability of the promoter to drive transcription of the bacterial chloramphenicol acetyltransferase gene. Using a series of 5'-end deletion mutants, we have identified multiple positive and negative cis-acting elements that regulate mouse neu gene transcription.
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PMID:Cloning and characterization of the mouse neu promoter. 134 55

The retinoblastoma susceptibility gene (Rb) is a tumor suppressor gene involved in the etiology of many types of human cancers. However, the molecular mechanisms involved in tumor suppression by Rb are largely unknown. The neu gene is a dominant transforming oncogene and a member of the growth factor receptor tyrosine kinase gene family. Both inactivation of the Rb gene and overexpression of the neu gene are involved in human breast and lung cancers. Therefore, it is of interest and importance to investigate the potential interactions between Rb and neu. Here we show that Rb suppresses neu-induced transformation by focus formation assays. This transformation suppression by Rb was further shown to be due to transcriptional repression of neu using Rb expressing effector plasmid and neu promoter-chloramphenicol acetyltransferase reporter gene. The cis-acting element conferring Rb-mediated repression was mapped to a recently identified novel enhancer in the neu promoter. The data indicate that the growth factor receptor neu is a target for the Rb gene product and transcriptional repression of a dominant oncogene expression may be one of the molecular mechanisms of Rb-mediated tumor suppression.
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PMID:The retinoblastoma gene product suppresses neu oncogene-induced transformation via transcriptional repression of neu. 135 Feb 77

Both neu gene overexpression and loss of estrogen receptor (ER) expression have been found to correlate with a poor prognosis in human breast cancer. Studies of breast tumor specimens have suggested that these two factors are not independent, leading us to hypothesize that there is a causal relationship between loss of ER and overexpression of neu. In this report, we confirm that ER can negatively regulate the expression of the neu gene protein product, p185neu, in two ER positive but not an ER negative breast cancer cell line(s). We have produced sublines which stably express human ER from a previously ER negative human breast cancer cell line. We demonstrate that the expression of ER in these cell lines is sufficient to confer the ability to respond to estradiol by down-regulating neu expression at both the protein and RNA levels. Utilizing neu promoter-chloramphenicol acetyltransferase constructs in transient cotransfection assays, we have also shown that this regulation occurs at the transcriptional level and requires the presence of both ER and estradiol. Furthermore, utilizing promoter deletion constructs, we provide evidence that a 140-base pair region of the neu promoter is required for this transcriptional regulation. When placed in a heterologous promoter, this 140-base pair region allows transcriptional repression by estradiol stimulated ER; thus, it represents an estrogen responsive region within the neu promoter. Finally, we have used gel mobility shift analysis to demonstrate an alteration in the nuclear factor(s) binding to this promoter region in estradiol stimulated versus estradiol deprived breast cancer cells. This study provides the first evidence that the inverse clinical correlation between neu and ER expression may be due to transcriptional repression of neu by estradiol stimulated ER.
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PMID:Transcriptional repression of the neu protooncogene by estrogen stimulated estrogen receptor. 135 36

We used chloramphenicol acetyltransferase (CAT) assays to identify and characterize cis-acting elements responsible for rat neu promoter function. Deletion of a region of the neu promoter (-504 to -312) resulted in a marked decrease in CAT activity, indicating that this promoter region corresponds to a positive cis-acting element. Using band shift assays and methylation interference analyses, we further identified a specific protein-binding sequence, AAGATAAAACC (-466 to -456), that binds a specific trans-acting factor termed RVF (for EcoRV factor on the neu promoter). The RVF-binding site is required for maximum transcriptional activity of the rat neu promoter. This same sequence is also found in the corresponding regions of both human and mouse neu promoters. Furthermore, this sequence can enhance the CAT activity driven by a minimum promoter of the thymidine kinase gene in an orientation-independent manner, and thus it behaves as an enhancer. Our results demonstrate that RVF is the major DNA-binding protein contributing to enhancer activity. In addition, Southwestern (DNA-protein) blot analysis using the RVF-binding site as a probe points to a 60-kDa polypeptide as a potential candidate for RVF.
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PMID:Identification and characterization of a novel enhancer for the rat neu promoter. 167 39

A 2.4-kb rat neu genomic DNA fragment that hybridized to the 5'-most coding sequence of the rat neu cDNA was cloned. S1 nuclease mapping identified multiple transcriptional initiation sites. DNA sequence analysis revealed that this fragment contained 64 bp of the first intron, 81 bp of the first exon, and the upstream noncoding sequence of the neu gene. The sequence immediately upstream of the translation start site was G + C rich (greater than 75%) and contained a consensus CCAAT sequence despite the absence of a TATA box. An Sp1-binding site was found, in addition to various sequence motifs common to the promoters of the human neu gene (erbB2), the epidermal growth factor receptor gene, and the simian virus 40 enhancer. A 2.2-kb EcoRI-Narl fragment containing sequences upstream from the 3'-most transcriptional start site was fused to the bacterial chloramphenicol acetyltransferase reporter gene and shown to promote transcription efficiently. A series of promoter deletion constructs was made, and results from transfection and subsequent chloramphenicol acetyltransferase assays suggested the presence of multiple cis-acting elements that contributed either positively or negatively to the transcription activity. Cotransfection competition experiments using subcloned cis-acting elements confirmed the existence of trans-acting factors interacting with these DNA fragments. In addition, a gel retardation assay was performed to demonstrate the physical binding of nuclear factors to certain fragments. The results complemented those of the deletion studies and led us to conclude that transcriptional regulation of the neu proto-oncogene involves at least one negative and three positive trans-acting factors interacting with different cis-acting elements along the neu gene promoter.
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PMID:Multiple cis- and trans-acting elements involved in regulation of the neu gene. 212 92

We have studied the ability of the neu tyrosine kinase to induce a signal for the activation of cell growth-regulated genes. Serum-starved NIH 3T3 cells expressing an epidermal growth factor receptor (EGF-R)/neu construct encoding a hybrid receptor protein were stimulated with EGF and the activation of the neu tyrosine kinase and stimulation of growth factor inducible genes were followed at the mRNA, protein, and activity levels, and compared to the corresponding responses in the neu proto-oncogene and oncogene expressing cells. Induction of the expression of jun mRNAs was an immediate early effect of EGF stimulation, followed by a marked increase in the biosynthesis of the fos/jun transcription factor complex and an increased transcription factor activity as measured by a recombinant transcription unit using chloramphenicol acetyltransferase assays. In distinction, elevated AP-1/PEA-1 activity in the absence of a significant increase in jun and fos expression was characteristic of the neu oncogene-expressing cells. The glucose transporter mRNA increased at 2 h of EGF stimulation and was associated with enhanced glucose transport of the EGF-treated cells. An increase of ornithine decarboxylase (ODC) mRNA and activity followed these changes. In contrast, serum-starved, EGF-treated neu proto-oncogene- and oncogene-expressing cells showed constitutively low and high glucose transporter and ODC activities, respectively. These findings demonstrate that the chimeric EGF-R/neu receptor is capable of activating the expression of both immediate early genes and biochemical activities associated with cell growth stimulation.
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PMID:Activation of the neu tyrosine kinase induces the fos/jun transcription factor complex, the glucose transporter and ornithine decarboxylase. 257 1

We localized the 5' region of the human gene HER2 in a cloned fragment of genomic DNA. This clone contained exons 1 to 4 of HER2, spanning the coding sequence for the first 191 amino acids. The promoter region of HER2 was identified upstream to exon 1 by nuclease S1 mapping and by a functional assay in which the promoter region drives the expression of a chloramphenicol acetyltransferase gene. The HER2 promoter is different from the promoter of the epidermal growth factor receptor gene (HER1), and the GC boxes which are typical of the promoter of the epidermal growth factor receptor gene are absent from the HER2 promoter. One major and two minor RNA start sites located at nucleotides 178, 244, and 257 upstream to the initiator ATG were identified. The first one is 21 and 70 base pairs downstream from typical TATAA and CAAT boxes, respectively. This indicates that transcription of HER2/neu can be regulated by a mechanism involving a TATA box, as well as by other unidentified regulatory elements.
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PMID:Human HER2 (neu) promoter: evidence for multiple mechanisms for transcriptional initiation. 303 51

The rat neu oncogene encodes a growth factor receptor-like glycoprotein, termed p185, that shares structural similarity with epidermal growth factor receptor (EGFR), particularly in the tyrosine-kinase domain. The Swiss Webster 3T3 murine embryo fibroblast (SW3T3) variant NR-6, in contrast to the parental cell line, does not express EGFR mRNA. After transfection of an activated rat neu cosmid clone, we demonstrated in this report that whereas SW3T3 cells readily expressed the exogenous rat p185 protein, NR-6 cells did not express detectable levels of this protein product. By transfection of plasmids containing the chloramphenicol acetyltransferase (CAT) gene driven by the neu promoter and subsequent CAT assays, we also showed that neu gene promoter activity was significantly less in NR-6 cells than in SW3T3 cells and that the neu promoter sequence responsible for this decreased transcription was a previously identified RVF enhancer element (Yan D-H, Hung M-C, Mol Cell Biol 11:1875-1882, 1991). That is to say, the RVF enhancer element of the neu promoter did not function as an enhancer in NR-6 cells. To investigate the mechanism responsible for the inactivation of RVF in NR-6 cells, we used southwestern blot analyses and demonstrated that the 60-kDa RVF polypeptide was present in both NR-6 and SW3T3 cell nuclear extracts. This result indicates that the DNA-binding activity of RVF was similar in these two cell lines; therefore, loss of RVF enhancer activity in NR-6 cells is probably due to inactivation of the trans-activating function and not DNA binding activity of RVF.
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PMID:Differential activity of the RVF enhancer element in the decreased expression of the neu oncogene in NR-6 cells versus parental Swiss Webster 3T3 cells. 809 19

Oncogenic transformation of fibroblasts by the src oncogene has long been known to cause an increase in the size of cell-surface protein-bound oligosaccharides, owing primarily to increased N-glycan branching mediated by increased beta-1,6-N-acetylglucosaminyltransferase V (GnT V) activity. The src-responsive element of the GnT V promoter was localized to Ets-binding sites and the promoter was transcriptionally stimulated by both ets-1 and ets-2 expression [Buckhaults, Chen, Fregien and Pierce (1997) J. Biol. Chem. 272, 19575-19581; Kang, Saito, Ihara, Miyoshi, Koyama, Sheng and Taniguchi (1996) J. Biol. Chem. 271, 26706-26712]. Because GnT V action requires the prior action of beta-1,2-N-acetylglucosaminyltransferase II (GnT II) and the human GnT II promoter contains four putative Ets-binding sites [Chen, Zhou, Tan and Schachter (1998) Glycoconj. J. 15, 301-308], GnT II might also be under oncogenic control via Ets transcription factors. We now report that co-transfection into HepG2 or COS-1 cells of either ets-1 or ets-2 expression plasmids together with chimaeric GnT II promoter-chloramphenicol acetyltransferase plasmids results in a 2-4-fold stimulation of promoter activity. Mobility-shift assays and South-Western blots localized the functional Ets-binding site to one of the four putative sites on the GnT II promoter. The GnT II promoter, unlike the GnT V promoter, is not activated by either src or neu. Therefore although both promoters are stimulated by a member of the Ets family of transcription factors, the functional role of this Ets transcriptional control seems to be different for the two genes.
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PMID:Regulation of expression of the human beta-1,2-N-acetylglucosaminyltransferase II gene (MGAT2) by Ets transcription factors. 1074 81