Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: EC:2.7.7.6 (RNA polymerase)
 34,946 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Control of tuberculosis is threatened by widespread emergence of drug resistance in Mycobacterium tuberculosis. Understanding the molecular basis of resistance might lead to development of novel rapid methods for diagnosing drug resistance. We set out to determine the molecular basis of resistance to rifampicin, a major component of multidrug regimens used for treating tuberculosis. Resistance to rifampicin involves alterations of RNA polymerase. The gene that encodes the RNA polymerase subunit beta (rpoB) was cloned. Sequence information from this gene was used to design primers for direct amplification and sequencing of a 411 bp rpoB fragment from 122 isolates of M tuberculosis. Mutations involving 8 conserved aminoacids were identified in 64 of 66 rifampicin-resistant isolates of diverse geographical origin, but in none of 56 sensitive isolates. All mutations were clustered within a region of 23 aminoacids. Thus, substitution of a limited number of highly conserved aminoacids encoded by the rpoB gene appears to be the molecular mechanism responsible for "single step" high-level resistance to rifampicin in M tuberculosis. This information was used to develop a strategy (polymerase chain reaction-single-strand conformation polymorphism) that allowed efficient detection of all known rifampicin-resistant mutants. These findings provide the basis for rapid detection of rifampicin resistance, a marker of multidrug-resistant tuberculosis.
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PMID:Detection of rifampicin-resistance mutations in Mycobacterium tuberculosis. 809 75

The rifampin resistance of Mycobacterium leprae is due to missense mutations in the rpoB gene encoding the beta-subunit of the essential enzyme RNA polymerase. A rapid and very simple method has been developed to detect rifampin resistance in small numbers of M. leprae present in biopsies. It involves polymerase chain reaction amplification of a defined region of the rpoB gene followed by single-strand conformational polymorphism analysis (PCR-SSCP). The reliability of the method has been tested on a sample of known drug-resistant and susceptible isolates of M. leprae.
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PMID:A simple and rapid technique for the detection of rifampin resistance in Mycobacterium leprae. 815 Nov 92

Drug-resistant tuberculosis has become a major public health problem. Resistance to rifampicin probably arises through mutations in the mycobacterial RNA polymerase. Patients may acquire rifampicin resistant tuberculosis by three mechanisms: (1) infection with a resistant organism, (2) selection of a sub-population of resistant organisms that remain contained whilst the more virulent wild type is present, (3) mutations within the population of bacilli causing the original infection. Sequential isolates of Mycobacterium tuberculosis were collected from 2 patients who developed rifampicin resistance whilst on treatment. One patient was immunosuppressed with HIV-infection; in the other patient the original isolate was also resistant to isoniazid. DNA fingerprinting techniques were used to type the isolates. No differences were found between the fingerprints of isolates from before and after the development of resistance. These data suggest that the third of the mechanisms listed above was responsible for the acquisition of rifampicin resistance in these 2 patients.
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PMID:DNA fingerprints of Mycobacterium tuberculosis do not change during the development of rifampicin resistance. 791 47

We have isolated RNA polymerase from Mycobacterium smegmatis and established conditions for specific transcription initiation in vitro. The M. smegmatis enzyme has a strong dependence on supercoiling of the DNA substrate for transcription from mycobacterial promoters. We also show that RNA polymerase is the target for rifampicin, and that this antibiotic specifically inhibits the transition from synthesis of short oligoribonucleotides to full-length transcripts. RNA polymerase isolated from a rifampicin-resistant mutant of M. smegmatis is less sensitive to rifampicin in vitro, confirming that one mechanism of rifampicin resistance in mycobacteria is through alteration of RNA polymerase. This in vitro transcription system provides a simple method for the characterization of gene expression in mycobacteria including the pathogens Mycobacterium tuberculosis, Mycobacterium avium and Mycobacterium leprae. It also provides a system for evaluating potential anti-mycobacterial drugs.
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PMID:Mycobacterium smegmatis RNA polymerase: DNA supercoiling, action of rifampicin and mechanism of rifampicin resistance. 831 80

The nucleotide sequence of cosmid B1790, carrying the Rif-Str regions of the Mycobacterium leprae chromosome, has been determined. Twelve open reading frames were identified in the 36716bp sequence, representing 40% of the coding capacity. Five ribosomal proteins, two elongation factors and the beta and beta' subunits of RNA polymerase have been characterized and two novel genes were found. One of these encodes a member of the so-called ABC family of ATP-binding proteins while the other appears to encode an enzyme involved in repairing genomic lesions caused by free radicals. This finding may well be significant as M. leprae, an intracellular pathogen, lives within macrophages.
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PMID:Nucleotide sequence of the first cosmid from the Mycobacterium leprae genome project: structure and function of the Rif-Str regions. 844 28

Rifampin is currently the most potent drug used in leprosy control programs. We show that the rifampin resistance which emerged in nine patients with lepromatous leprosy, who had received rifampin monotherapy, stemmed from mutations in the rpoB gene, which encodes the beta subunit of RNA polymerase of Mycobacterium leprae. In eight cases missense mutations were found to affect a serine residue, Ser-425, while in the remaining mutant a small insertion was found close to this site. These findings will be of use for the development of a rapid screening procedure, involving the polymerase chain reaction, for monitoring the emergence of rifampin-resistant M. leprae strains.
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PMID:Molecular basis of rifampin resistance in Mycobacterium leprae. 846 Sep 11

The application of molecular biology techniques to the diagnosis of mycobacteriosis was evaluated. The hybridization protection assay (HPA) was found to be accurate and rapid in the identification of mycobacteria. The nested polymerase chain reaction (PCR) targeting the Pab gene was specific and sensitive enough for the rapid detection of Mycobacterium tuberculosis in clinical specimens. The overall sensitivity and specificity of the nested PCR were excellent, 97% and 92%, respectively. In addition, a novel method combining the PCR and the HPA for the rapid detection of MAC and M. tuberculosis was developed. This method was as useful as the nested PCR for M. tuberculosis above mentioned. The clinical usefulness of two commercially available mycobacteria detection kits, the MTD and the Amplicor, was evaluated and compared with that of the conventional smear and culture methods. The MTD showed the highest sensitivity, while the Amplicor showed the highest specificity. The HPA was also applied to drug susceptibility tests, which require 3 to 4 weeks by conventional methods. By this method, the results of resistance to isoniazid or rifampicin could be obtained after three days incubation. Another method for determining the drug resistance of mycobacteria is the detection of gene alterations related to the drug resistance. The deletion of the catalase-peroxidase gene related to isoniazid resistance was observed in 15% of isoniazid-resistant strains. On the other hand, point mutations in the RNA polymerase beta subunit (rpoB) gene relating to rifampicin resistance were detected in 31% of rifampicin-resistant strains by the non-radioisotope PCR-SSCP analysis.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:[The application of molecular biology to the diagnosis of mycobacteriosis]. 852 54

The rpoB gene encodes the beta subunit of the DNA-dependent RNA polymerase of bacteria. Mutations in defined areas result in resistance to rifampin. Mycobacterium smegmatis is naturally resistant to rifampin, but analysis of the rpoB gene revealed no identifiable rifampin resistance mutations. Another mechanism of resistance may be present.
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PMID:Sequence and analysis of the rpoB gene of Mycobacterium smegmatis. 854 Jul 40

Four rpoD hybridizing signals have been identified in the chromosome of Brevibacterium lactofermentum. Two rpoD-like genes, sigA and sigB, have been cloned and sequenced, and they encode principal sigma factors of the RNA polymerase. The deduced amino acid sequences of SigA and SigB showed very high similarities to those of Mycobacterium smegmatis MysA and MysB proteins, respectively, and also to those of HrdB proteins from different Streptomyces species. SigA and SigB maintain the conserved motifs of sigma 70-like principal sigma factors. sigB is closely linked to the dtxR gene (encoding a repressor of iron-regulated promoters homologous to the diphtheria toxin repressor from Corynebacterium diphtheriae.
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PMID:Multiple sigma factor genes in Brevibacterium lactofermentum: characterization of sigA and sigB. 855 Apr 80

Historically, infections caused by Mycobacterium tuberculosis have been treated simultaneously with isoniazid and rifampin. As a consequence of this combined therapy, strains resistant only to rifampin were rarely recovered. However, recently there has been an increasing number of reports describing HIV-positive patients infected with mono-rifampin-resistant M. tuberculosis strains. Organisms cultured from seven patients (including six with AIDS) with infections caused by mono-rifampin-resistant M. tuberculosis, and seen at one New York City hospital, were analyzed by molecular techniques to test the hypothesis that dissemination of a single clone had occurred. IS6110 DNA fingerprinting and automated DNA sequencing of a region of the RNA polymerase beta subunit structural gene (rpoB) containing mutations that confer rifampin resistance showed that all organisms independently acquired the mono-rifampin-resistant phenotype. Molecular analysis of mono-rifampin-resistant organisms cultured from 13 additional patients in New York City confirmed independent strain origin. The data rule out the possibility of person-to-person strain transmission among these patients, and they suggest that host factors such as poor compliance with antituberculosis medications or decreased absorption of rifampin have been a driving force in the origin of these strains.
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PMID:Independent origin of mono-rifampin-resistant Mycobacterium tuberculosis in patients with AIDS. 888 22


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