Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UNIPROT:P06889 (Mol)
 630,302 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Methyl methanesulfonate (MMS), a direct mutagen, methylates DNA bases and causes distortions in DNA structure. Supercoiled SV40 DNA was treated in vitro with varying concentrations of MMS from 0.001 mM to 10 mM MMS either for 30 min or 3 h and analysed by electrophoresis in 1% neutral and alkaline agarose gels. The electrophoretic mobility (EPM) of native DNA did not change after treatment with the mutagen, while alkaline gels revealed low MW DNA fragments due to single strand breaks at alkali-sensitive sites generated by the action of MMS. By two-dimensional electrophoresis, we find that all three native DNA forms contain alkali-sensitive sites after treatment with MMS. To examine the effect of base modification by MMS on DNA-protein interactions, we have used as probes, restriction endonucleases. These cleave DNA in a sequence-specific manner, and their activity is dependent upon the methylation status of the substrate DNA. We find that cleavage by these restriction endonucleases is inhibited due to methylation by MMS.
Cell Mol Biol Res 1995
PMID:Inhibition of cleavage by restriction endonucleases due to modifications induced in SV40 DNA by methyl methanesulfonate. 755 Apr 53

We have used the lacZ reversion assay to study the mutation spectra induced by the Escherichia coli chromosomal umuDC operon and of its two plasmid-borne analogues impCAB and mucAB following exposure of cells to UV light and methyl methanesulfonate (MMS). We have shown that the impCAB, mucAB and umuDC operons all produce a similar response to UV light which results almost exclusively in AT-->GC transitions. However, we found that the three operons produced different responses to alkylating agents. We found that with MMS the chromosomal umuDC operon produced almost exclusively AT-->GC transitions, whilst both mucAB and impCAB produced predominantly transversions. In the case of the impCAB operon the mutation spectrum contained more AT-->TA than GC-->TA transversions; this balance was reversed with mucAB. The effect of the copy number of the error-prone DNA repair operons upon the mutagenic spectra was also studied. The results obtained suggest that the copy number of the imp operon does not greatly affect the specificity of base substitutions observed. However, an increase in the copy number of the umuDC operon greatly affected the specificity of base substitution, such that virtually no transitions were produced and the spectrum was dominated by GC/AT-->TA transversions. It appears that the three error-prone DNA repair operons impCAB, mucAB and umuDC, despite showing strong structural and functional homologies, can display major differences in the spectrum of base changes induced during mutagenesis.(ABSTRACT TRUNCATED AT 250 WORDS)
Mol Gen Genet 1995 Jun 25
PMID:The spectra of base substitutions induced by the impCAB, mucAB and umuDC error-prone DNA repair operons differ following exposure to methyl methanesulfonate. 761 65

A new mutation in Escherichia coli K12, isfA, is described, which causes inhibition of SOS functions. The mutation, discovered in a delta polA+ mutant, is responsible for inhibition of several phenomena related to the SOS response in polA+ strains: UV- and methyl methanesulfonate-induced mutagenesis, resumption of DNA replication in UV-irradiated cells, cell filamentation, prophage induction and increase in UV sensitivity. The isfA mutation also significantly reduces UV-induced expression of beta-galactosidase from recA::lacZ and umuC'::lacZ fusions. The results suggest that the isfA gene product may affect RecA* coprotease activity and may be involved in the regulation of the termination of the SOS response after completion of DNA repair. The isfA mutation was localized at 85 min on the E. coli chromosome, and preliminary experiments suggest that it may be dominant to the wild-type allele.
Mol Gen Genet 1995 Jul 22
PMID:A new mutation in Escherichia coli K12, isfA, which is responsible for inhibition of SOS functions. 765 21

The uvsH DNA repair gene of Aspergillus nidulans has been cloned by complementation of the uvsH77 mutation with a cosmid library containing genomic DNA inserts from a wild-type strain. Methylmethane sulfonate (MMS)-resistant transformants were obtained on medium containing 0.01% MMS, to which uvsH mutants exhibit high sensitivity. Retransformation of uvsH77 mutants with the rescued cosmids from the MMS-resistant transformants resulted in restoration of both UV and MMS resistance to wild-type levels. Nucleotide sequence analysis of the genomic DNA and cDNA of the uvsH gene shows that it has an open reading frame (ORF) of 1329 bp, interrupted by two introns of 51 and 61 bp. A 2.4 kb transcript of the uvsH gene was detected by Northern blot analysis. Primer extension analysis revealed that transcription starts at 31 bp upstream from the translation initiation codon. This gene encodes a predicted polypeptide of 443 amino acids, which has two unique zinc finger motifs. The proposed polypeptide displays 39% identity to the Neurospora crassa UVS-2 protein and 24% identity to the Saccharomyces cerevisiae RAD18 protein. The sequence similarity is particularly high in three domains. One zinc finger (RING finger) motif is located in the first domain close to the N-terminus. The other zinc finger motif is in the second domain. In the third domain, the mutation sites in both the uvsH77 and uvsH304 alleles were identified.(ABSTRACT TRUNCATED AT 250 WORDS)
Mol Gen Genet 1995 Jul 28
PMID:The Aspergillus uvsH gene encodes a product homologous to yeast RAD18 and Neurospora UVS-2. 765 40

It has been suggested that transposable elements can be associated with different types of genotoxic effects. For this reason it seems appropriate to outline suitable systems to detect changes in the phenotypic expression of the loci containing transposable elements, as well as those agents that induce such changes. The sex-linked white locus offers a suitable experimental system for studying such events because most of the spontaneous mutations at the white locus are the result of insertions of repeated mobile sequences, and it is easy to follow mutational changes of the locus due to the possibility of detecting even slight changes in eye color. Here we report the results obtained in different strains of Drosophila melanogaster with copia-like induced mutations at the white locus, after treatment with three alkylating agents: ethyl methanesulfonate (EMS), methyl methanesulfonate (MMS), and N-nitroso-N-ethylurea (ENU). The three insertional white mutants used in this work were wa4, wbf, and wsp55, with the wa2 mutation used as control because its mutant phenotype is the result of a point mutation instead of the insertion of a DNA fragment. Our data constitute evidence that EMS, MMS, and ENU induce a clear increase in the frequencies of somatic-revertant sectors in the three strains carrying a white allele with an inserted copia-like element. For the wa2 strain, whose mutant phenotype is the result of a point mutation, only ENU at the highest concentration tested is able to induce a significant increase in the somatic reversion frequency. In addition, our results indicate that the use of D. melanogaster strains with transposable elements in the white locus is suitable for detecting genotoxic damage induced by chemicals.
Environ Mol Mutagen 1995
PMID:Somatic reversion of some copia-like induced mutations, at the white locus of Drosophila melanogaster, after treatment with alkylating agents. 769 6

In this report we characterized the transcriptional regulation of the rat mdr1b gene by xenobiotics. The expression of this gene was increased in primary rat hepatocytes and in the H4-II-E hepatoma cell line by exposure to carcinogens such as aflatoxin B1, N-acetoxy-2-acetylaminofluorene, and methyl methanesulfonate. Nuclear run-on experiments indicated that the higher steady-state levels of mdr1b mRNA were due to an increase in transcription. The 5'-flanking region of the mdr1b gene was isolated, sequenced, and functionally characterized in transient and stable transfection assays. A single transcription start site was identified for this gene; no alternate start sites were used after induction with aflatoxin B1. Deletion analysis of this promoter demonstrated that the sequence between nt -214 and -178 was critical for basal promoter activity. This region did not contain any consensus-binding sites for previously identified transcription factors. A negative regulatory region was also identified between nt -940 and -250. No specific carcinogen-responsive element was identified; the xenobiotic response required a large part of the promoter. These data suggest that the carcinogen induction of mdr1b expression is mediated through sequences that overlap or that are identical to the basal promoter element.
Mol Carcinog 1995 May
PMID:Characterization of the basal and carcinogen regulatory elements of the rat mdr1b promoter. 776 10

It has been found that the level of methyl methanesulfonate (MMS)-induced mutation in Escherichia coli is dependent on the level of UmuD(D')C proteins. The frequency of argE(ochre)-->Arg+ mutations (which occur predominantly by AT-->TA transversions) and RifS-->RifR mutations is much higher when UmuDC or UmuD'C are overproduced in the cell. When MMS-treated bacteria were starved for progressively longer times and hence the expression of mutations delayed, the level of mutations observed progressively declined. This same treatment had no effect on the degree of SOS induction. Examination of plasmid DNAs, isolated from MMS-treated cells, for their sensitivity to the specific endonucleases Fpg and Nth revealed that MMS causes formation of abasic sites, which are repaired during cell starvation. It is assumed that, in non-dividing cells, apurinic sites are mostly repaired by RecA-mediated recombinational repair. This pathway, which is error-free, is compared with the processing pathway in metabolically active cells, where translesion synthesis by the UmuD'2C-RecA-DNA polymerase III holoenzyme complex occurs; this latter pathway is error-prone.
Mol Gen Genet 1994 Nov 15
PMID:The frequency of MMS-induced, umuDC-dependent, mutations declines during starvation in Escherichia coli. 780 98

The mei-41 gene of Drosophila melanogaster plays an essential role in meiosis, in the maintenance of somatic chromosome stability, in postreplication repair and in DNA double-strand break repair. This gene has been cytogenetically localized to polytene chromosome bands 14C4-6 using available chromosomal aberrations. About 60 kb of DNA sequence has been isolated following a bidirectional chromosomal walk that extends over the cytogenetic interval 14C1-6. The breakpoints of chromosomal aberrations identified within that walk establish that the entire mei-41 gene has been cloned. Two independently derived mei-41 mutants have been shown to carry P insertions within a single 2.2 kb fragment of the walk. Since revertants of those mutants have lost the P element sequences, an essential region of the mei-41 gene is present in that fragment. A 10.5 kb genomic fragment that spans the P insertion sites has been found to restore methyl methanesulfonate resistance and female fertility of the mei-41D3 mutants. The results demonstrate that all the sequences required for the proper expression of the mei-41 gene are present on this genomic fragment. This study provides the foundation for molecular analysis of a function that is essential for chromosome stability in both the germline and somatic cells.
Mol Gen Genet 1995 Jan 20
PMID:Molecular cloning of mei-41, a gene that influences both somatic and germline chromosome metabolism of Drosophila melanogaster. 786 85

The degradation of many proteins involves the sequential ligation of ubiquitin molecules to the substrate to form a multiubiquitin chain linked through Lys-48 of ubiquitin. To test for the existence of alternate forms of multiubiquitin chains, we examined the effects of individually substituting each of six other Lys residues in ubiquitin with Arg. Substitution of Lys-63 resulted in the disappearance of a family of abundant multiubiquitin-protein conjugates. The UbK63R mutants were not generally impaired in ubiquitination, because they grew at a wild-type rate, were fully proficient in the turnover of a variety of short-lived proteins, and exhibited normal levels of many ubiquitin-protein conjugates. The UbK63R mutation also conferred sensitivity to the DNA-damaging agents methyl methanesulfonate and UV as well as a deficiency in DNA damage-induced mutagenesis. Induced mutagenesis is mediated by a repair pathway that requires Rad6 (Ubc2), a ubiquitin-conjugating enzyme. Thus, the UbK63R mutant appears to be deficient in the Rad6 pathway of DNA repair. However, the UbK63R mutation behaves as a partial suppressor of a rad6 deletion mutation, indicating that an effect of UbK63R on repair can be manifest in the absence of the Rad6 gene product. The UbK63R mutation may therefore define a new role of ubiquitin in DNA repair. The results of this study suggest that Lys-63 is used as a linkage site in the formation of novel multiubiquitin chain structures that play an important role in DNA repair.
Mol Cell Biol 1995 Mar
PMID:A ubiquitin mutant with specific defects in DNA repair and multiubiquitination. 786 20

The Acinetobacter calcoaceticus pcaJ and catJ genes, nearly identical in DNA sequence, differ in transcriptional control and are separated by more than 20 kb of chromosomal DNA. The pcaJ3125 mutation is repaired frequently in organisms containing the wild-type catJ gene. This high-frequency repair is eliminated in strains lacking the catJ gene, which suggests that recombination between the homologous catJ and pcaJ genes contributes to the high-frequency repair of the pcaJ3125 mutation. We report here that the high-frequency repair also requires a functional recA gene. The A. calcoaceticus recA gene was cloned in Escherichia coli by complementation of a recA mutation in the host strain. The nucleotide sequence of a 1506 bp DNA fragment containing A. calcoaceticus recA was determined. The amino acid sequences of RecA from E. coli and A. calcoaceticus shared 71% identity. The DNA sequences differed in that a consensus binding site for binding of LexA repressor, represented upstream from recA in E. coli, is not evident in the corresponding region of the A. calcoaceticus DNA sequence. A Tn5 insertion was introduced into the A. calcoaceticus recA gene. Selection for Tn5-encoded kanamycin resistance allowed the inactivated recA gene to be recombined by natural transformation into the A. calcoaceticus chromosome. Strains that had acquired the mutant gene were sensitive to both MMS and u.v. light, were deficient in natural transformation, and failed to carry out catJ-dependent high-frequency repair of the pcaJ3125 mutation.
Mol Microbiol 1994 Jun
PMID:Properties of Acinetobacter calcoaceticus recA and its contribution to intracellular gene conversion. 793 5


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