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)

Human selenium-dependent glutathione peroxidase (hGPx1) (EC 1.11.1.9) is thought to be involved in many critical cellular functions as a result of its role in glutathione-mediated reduction of toxic peroxides, and it is implicated as a mechanism of resistance against oxygen free radicals. Previous studies have demonstrated that the gene encoding hGPx1 (hgpx1) is more highly expressed in multidrug-resistant AdrR MCF-7 human breast cancer cells than in the parental WT MCF-7 cell line. In order to further study the transcriptional regulation of hgpx1, we have cloned the genomic hgpx1 gene and determined its nucleotide sequence. The 2550-base pair (bp) 5'-flanking sequence of hgpx1 contained the terminal 511 bp of the 3' end of a previously reported rhoH12 cDNA (Yeramian, P., Chardin, P., Madaule, P., and Tavitian, A. (1987) Nucleic Acids Res. 15, 1989), a ras-related oncogene. Further downstream from rhoH12, but before the start of transcription of hgpx1, RNase protection analysis revealed a transcribed sequence of at least 270 bp which we have called mid. RNA transcripts homologous to both rhoH12 (1.8 and 1.5 kilobase pairs (kb)) and mid (1.8 kb) are also more highly expressed in AdrR MCF-7 cells than in WT MCF-7 cells. We screened an AdrR MCF-7 cDNA library with the mid sequence and isolated a partial cDNA clone which contains both mid and rhoH12 sequences and is colinear with the genomic sequence which extends from 10 bp 3' to the rhoH12 stop codon to 810 bp 5' to the start of transcription of hgpx1. The start of transcription of hgpx1 in AdrR MCF-7 cells was determined by primer extension analysis. The promoter and 2 kb of the 5'-flanking sequence of hgpx1 was fused to the bacterial chloramphenicol acetyltransferase gene (hGPx1-CAT1). Analysis of deletion constructs of hGPx1-CAT1 revealed three possible cis-acting regulatory regions. The transcriptional regulation of hgpx1 was examined using the hGPx1-CAT hybrid genes and nuclear run-on studies. We found no evidence that increased mRNA transcript formation could account for different levels of hgpx1 RNA either in different breast cancer cell lines or in response to selenium.
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PMID:Structure and function of the 5'-flanking sequence of the human cytosolic selenium-dependent glutathione peroxidase gene (hgpx1). 155 8

The role of the carboxy terminal in folding and stabilization of type I chloramphenicol acetyltransferase (CAT1) has been studied by mutagenesis and Fourier transform infrared analysis. We have shown that a CAT mutant truncated by seven amino acid residues folds into active protein. In this study, the last three residues of this truncated CAT mutant were randomized to detect structural information required for achieving a native enzyme conformation. Statistical analysis of sequencing data from randomly chosen mutants revealed that the amino-terminal CAT fragment of 212 amino acid residues is the shortest deletion mutant able to adopt a soluble, enzymatically active structure. This minimal length corresponds to a protein with full-length alpha5-helix in the three-dimensional crystal structure of CAT type III. The amino acid preferences at the carboxy terminal in the randomization experiments suggest that this helix also forms completely in the shortened CAT mutants. In addition correct folding and/or stabilization requires the formation of a hydrophobic + microdomain at the end of the alpha5-helix. The role of this hydrophobic interaction in CAT folding and structure stabilization is discussed.
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PMID:Identification of local carboxy-terminal hydrophobic interactions essential for folding or stability of chloramphenicol acetyltransferase. 860 39

GH-releasing hormone (GHRH) is a hypothalamic peptide that plays a critical role in controlling the synthesis and secretion of GH in the anterior pituitary. Along with many other hypothalamic hormones, GHRH is also expressed in the placenta, although its physiological role in this tissue has not yet been determined. The placental prepro-GHRH is identical to that found in the hypothalamus. However, the placental and hypothalamic GHRH messenger RNAs differ in the region corresponding to the untranslated exon 1. A combined mechanism involving the use of tissue-specific promoters and the differential splicing of exon 1 generates the mature GHRH messenger RNAs in placenta and hypothalamus. As a first step toward the localization of the regulatory elements involved in the placenta-specific expression of the GHRH gene, we have generated transgenic mice containing constructs in which potential regulatory sequences of the rat GHRH gene were fused to the chloramphenicol acetyltransferase (CAT) reporter gene. Construct GHRH-CAT1, which contains 7.5 kilobases of flanking sequences upstream to the placental transcription start site, did not promote CAT expression in the transgenic animals. In contrast, construct GHRH-CAT2, which differs from construct GHRH-CAT1 in having additional sequences located downstream to placental exon 1, exhibited high levels of CAT expression in brain and placenta. Our results show that the sequences included in construct GHRH-CAT2 contain the cis-acting regulatory elements necessary to direct developmentally regulated and cell type-specific expression of the CAT gene in the placenta. Unexpectedly, the expression of the transgene in the brain was detected in glial cells of different areas, but not in the hypothalamus.
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PMID:Placenta-specific expression of the rat growth hormone-releasing hormone gene promoter in transgenic mice. 923 71