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)

Presented here is an experimental demonstration of our theoretical predictions on the role of the downstream context of unfavourable codons in a gene on its expression level. Six non clustered AGG codons were inserted in the chloramphenicol acetyltransferase (cat) gene of E. coli and the expression of this modified gene (cat4) was compared with that of a cat gene in which four clustered AGG codons were inserted (cat2 gene). As predicted, the rate of production of the corresponding CAT4 and CAT2 proteins is equal as long as the rate of transcription of the gene does not exceed a given limit. When this limit is exceeded, production of CAT4 continues to increase, whereas CAT2 production decreases dramatically. Various consequences and possible applications of this downstream context effect are discussed.
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PMID:The maximum rate of gene expression is dependent on the downstream context of unfavourable codons. 251 83

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

Human thioredoxin (Trx) is a 12-kD protein known to be involved in various reduction/oxidation reactions essential for cell growth and cellular injury repair. We previously demonstrated, based on nuclear run-on assay, that retinoic acid (RA) stimulated Trx gene expression in airway epithelial cells at the transcriptional level. Nucleotide sequencing of the 5'-flanking region of the human Trx gene revealed the presence of a TATA box at -28 and four RA response element (RARE)-like half sites at -426, -453, -507, and -626 nt. Transient transfection assays with a Trx promoter-reporter gene, chloramphenicol acetyltransferase (CAT), demonstrated a dose-dependent involvement of these four RARE-like half sites in RA-enhanced promoter activity. When the DNA fragment that flanks these four RARE-like half sites from -357 to -671 nt was introduced into a heterologous promoter of the tk-CAT2 vector, both basal and RA-stimulated CAT activities were observed. A site-directed mutagenesis approach demonstrated an essential role for RARE-I and RARE-II at -426 and -453 nt, respectively, and an auxiliary role for RARE-III at -507 nt in both basal and RA-stimulated CAT activities. Both in vivo and in vitro genomic footprinting experiments further demonstrated specific protein-DNA interactions in these "putative" RARE-I/II/III half sites. Gel electrophoretic mobility shift assays demonstrated specific interactions of these RARE-like half sites with the nuclear extracts obtained from RA-treated cultures. The anti-RAR-alpha antibody super-shift experiment further confirmed the interactions of RARE-I/II sites with RAR-alpha nuclear receptor. These results suggest a classic RARE/RAR interaction involved in RA-stimulated Trx gene expression in human airway epithelium.
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PMID:Regulation of thioredoxin gene expression by vitamin A in human airway epithelial cells. 1197 Sep 16