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)

Cockayne syndrome (CS) and xeroderma pigmentosum (XP), autosomal recessive diseases with clinical and cellular hypersensitivity to UV radiation, differ in ability to repair UV DNA photoproducts in their overall genome: normal repair in CS, defective repair in XP. In order to characterize a DNA repair defect in an active gene in CS, we measured the capacity of cells from patients with CS and XP to reactivate 2 major types of UV-induced DNA damage, photoreactivatable (i.e., cyclobutane pyrimidine dimers) and non-photoreactivatable (primarily pyrimidine-(6-4)pyrimidone photoproducts), in the actively transcribing chloramphenicol acetyltransferase (cat) gene of the plasmid expression vector pRSV-cat. Epstein-Barr virus-transformed lymphoblast lines from 4 normal persons and from 3 patients with CS and from two with XP were transiently transfected with the plasmid, and the cat activity in cell extracts was determined. When the cells were transfected with UV-irradiated plasmid, expression was abnormally decreased in both the CS and XP cells. When the cyclobutane pyrimidine dimers in the UV-irradiated plasmid were removed by photoreactivation prior to transfection, cat expression in the CS, but not in the XP, lines reached normal levels. These data imply that both the XP and CS cells are unable to repair normally the cyclobutane pyrimidine dimer photoproducts which block transcription of cat. However, the CS, but not XP, cells can repair normally the other UV-induced photoproducts which block transcription. The ability of CS, but not XP, cells to repair these non-dimer photoproducts indicates that the active gene repair mechanism treats the cyclobutane pyrimidine dimer differently from the non-dimer photoproducts.
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PMID:Evidence for defective repair of cyclobutane pyrimidine dimers with normal repair of other DNA photoproducts in a transcriptionally active gene transfected into Cockayne syndrome cells. 171

Transfected recombinant DNA with regulatory elements such as eukaryotic promoter and termination sites is transiently expressed in human fibroblast cells. Utilizing an expression vector containing the simian virus 40 (SV 40) early control region followed by the E. coli chloramphenicol acetyltransferase (CAT) gene, we investigated the ability of normal, Xeroderma pigmentosum and Cockayne Syndrome cells to repair UV lesions in transfected DNA. Fibroblasts from Xeroderma pigmentosum patients which cannot excise pyrimidine cyclobutane dimers were unable to restore expression of UV irradiated CAT gene. An UV dose inducing one thymine cyclobutane dimer in the transcribed strand of the CAT gene blocked its transcription in these repair deficient cells. Normal cell were able to repair the lesions in transfected DNA during an incubation period of about 40 h and in this way could overcome the UV block. In several fibroblast cell lines from patients suffering from Cockayne Syndrome expression of UV damaged CAT gene was restored significantly less than in normal fibroblasts, indicating that Cockayne Syndrome is associated with a UV repair defect.
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PMID:Transient expression of a plasmid gene, a tool to study DNA repair in human cells: defect of DNA repair in Cockayne syndrome; one thymine cyclobutane dimer is sufficient to block transcription. 395 12

Nucleotide excision repair (NER)-deficient human cells have been assigned so far to a genetic complementation group by a somatic cell fusion assay and, more recently, by microinjection of cloned DNA repair genes. We describe a new technique, based on the host cell reactivation assay, for the rapid determination of the complementation group of NER-deficient xeroderma pigmentosum (XP), Cockayne's syndrome (CS) and photosensitive trichothiodystrophy (TTD) human cells by cotransfection of a UV-irradiated reporter plasmid with a second vector containing a cloned repair gene. Expression of the reporter gene, either chloramphenicol acetyltransferase (CAT) or luciferase, reflects the DNA repair ability restored by the introduction of the appropriate repair gene. All genetically characterized XP, CS and TTD/XP-D cells tested failed to express the UV-irradiated reporter gene, this reflecting their NER deficiency whereas cotransfection with the repair plasmid expressing a gene specific for the given complementation group increased the enzyme activity to the level reached by normal cells. Selective recovery of both reporter enzyme activities was observed after cotransfection with the XPC gene for the XP17VI cells and with the XPA gene for both XP18VI and XP19VI cells. Using this method, we assigned three new NER-deficient human cells obtained from patients presenting clinical symptoms described as classical XP to either XP group A (XP18VI and XP19VI) and XP group C (XP17VI). Therefore, this technique increases the range of methods now available to determine the complementation group of new NER deficient patients with the advantage, unlike the somatic cell fusion assay or the microinjection procedure, of being simple, rapid, and inexpensive.
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PMID:Development of a new easy complementation assay for DNA repair deficient human syndromes using cloned repair genes. 776 57