Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UNIPROT:P01034 (cystatin C)
 3,397 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Genetic analysis of histidine independent (His+) revertants induced by ultraviolet light in the his-4 E. coli strain AB1157 was carried out: 93% carried ochre (UAA) suppressor mutations and 17% carried back mutations to his+ or (intragenic?) suppressors not detectably separable from his-4. Using the specialized transducing lambda psu 2int- phage, which carries supE-supB, it was determined that 87% of the ochre suppressors mapped in the supE-supB region. We were able to deduce that 56% of these affected tRNA1Gln by a CAA leads to TAA change in the tRNA gene while 31% affected tRNA2Gln by TAG- leads to TAA change. Although we were unable to deduce the base substitution of the remaining 13%, the results indicate that most of the suppressor mutations are caused by G:C to A:T transition. These results suggest that the high incidence of supE-supB region suppressor mutation in E. coli by UV would be a reflection of the general feature of UV mutagenesis; i.e. preferential induction of G:C to A:T transition in repairing nonpairing DNA lesions. AI 05371
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PMID:Analysis of ultraviolet light-induced suppressor mutations in the strain of Escherichia coli K-12 AB1157: an implication for molecular mechanisms of UV mutagenesis. 645 Aug 70

Chloroacetaldehyde-modified poly(rC) or poly(dC) was prepared containing either 8-36% 3,N4-ethenocytidine (epsilon C) or 8-36% of a mixture of epsilon C and the hydrated epsilon C (epsilon C . H2O), with the hydrate greatly predominating (greater than 90%). These ribo- and deoxyribonucleotide templates were transcribed with DNA-dependent RNA polymerases from Escherichia coli and calf thymus, in the presence of either Mn2+ or Mg2+ and all four ribonucleoside triphosphates. All the polymers tested were transcribed with either cation present. In an earlier report from this laboratory [Spengler, S., & Singer, B. (1981) Nucleic Acids Res. 9. 365], transcriptional ambiguities resulting from epsilon C residues in enzymatically synthesized poly(rC, epsilon rC) were studied with E. coli DNA-dependent RNA polymerase in the presence of Mn2+. The misincorporations there reported were confirmed when poly(rC, epsilon rC) and poly(dC, epsilon dC), prepared by reaction of poly(rC) and poly(dC) with CAA, were transcribed in the presence of either Mn2+ or Mg2+. We now report that the presence of hydrated epsilon C in polymers also leads to misincorporations but with reproducible differences from those found with epsilon C alone. Nearest-neighbor analysis of the transcription products showed that the hydrate caused misincorporation of A greater than U much greater than C while epsilon C caused misincorporation of U greater than A much greater than C. The extent of misincorporation in transcription was less with Mg2+ than with Mn2+, but the pattern of ambiguity was the same with both cations and with both ribo- and deoxyribocytidylate polymers. Calf thymus DNA-dependent RNA polymerase IIB was also used to transcribe deoxyribocytidine polymers with Mn2+ as the cation. epsilon C and epsilon C . H2O both caused a high level of misincorporation of U , A, and C, but the preferred misincorporations differed slightly from those found with E. coli DNA-dependent RNA polymerase. For both prokaryotic and eukaryotic enzymes, the type of misincorporation resulting from the loss of hydrogen bonding by modification of the N-3 of C not only differed between epsilon C and the hydrated intermediate but also both differed from the transcriptional errors resulting from the presence of 3-methylcytidine in poly(dC) or poly(rC). We conclude that the errors made by these polymerases during transcription do not result primarily from the conditions used (cation, ribo- or deoxyribotemplate) but must be at least in part attributed to the enzyme recognizing some facet of the modified base other than the lack of normal hydrogen bonding.
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PMID:Chloroacetaldehyde-treated ribo- and deoxyribopolynucleotides. 2. Errors in transcription by different polymerases resulting from ethenocytosine and its hydrated intermediate. 675 74

Mouse skin tumors contain activated c-H-ras oncogenes, often caused by point mutations at codons 12 and 13 in exon 1 and codons 59 and 61 in exon 2. Mutagenesis by the noncoding apurinic sites can produce G-->T and A-->T transversions by DNA misreplication with more frequent insertion of deoxyadenosine opposite the apurinic site. Papillomas were induced in mouse skin by several aromatic hydrocarbons, and mutations in the c-H-ras gene were determined to elucidate the relationship among DNA adducts, apurinic sites, and ras oncogene mutations. Dibenzo[a,l]pyrene (DB[a,l]P), DB[a,l]P-11,12-dihydrodiol, anti-DB[a,l]P-11,12-diol-13,14-epoxide, DB[a,l]P-8,9-dihydrodiol, 7,12-dimethylbenz[a]anthracene (DMBA), and 1,2,3,4-tetrahydro-DMBA consistently induced a CAA-->CTA mutation in codon 61 of the c-H-ras oncogene. Benzo[a]pyrene induced a GGC-->GTC mutation in codon 13 in 54% of tumors and a CAA-->CTA mutation in codon 61 in 15%. The pattern of mutations induced by each hydrocarbon correlated with its profile of DNA adducts. For example, both DB[a,l]P and DMBA primarily form DNA adducts at the N-3 and/or N-7 of deoxyadenosine that are lost from the DNA by depurination, generating apurinic sites. Thus, these results support the hypothesis that misreplication of unrepaired apurinic sites generated by loss of hydrocarbon-DNA adducts is responsible for transforming mutations leading to papillomas in mouse skin.
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PMID:Relating aromatic hydrocarbon-induced DNA adducts and c-H-ras mutations in mouse skin papillomas: the role of apurinic sites. 747 97

Cells have been isolated from liver tumours that have arisen in control C3H/He mice, in mice given 10 micrograms diethylnitrosamine (DEN) during the neonatal period or in mice given a diet containing phenobarbitone (PB) to allow a daily intake of 85 mg/kg/day. The cells were grown to the 8 degrees subculture when their growth characteristics were investigated in monolayer culture and following suspension in soft agar and on transplantation into nude mice. In addition, DNA was isolated from the cultures and from tumours that grew in nude mice and analysed for mutations at codon 61 of the Ha-ras oncogene. All cells derived from DEN-induced hepatocellular carcinomas (HCC) demonstrated a lack of density inhibition of growth in monolayer culture, grew in soft agar and formed tumours in nude mice with an average mean latency of 29 days. Three of the seven lines showed mutations in Ha-ras: two were CAA-->AAA transversions and one showed a CAA-->CTA transversion. In contrast, cells isolated from eosinophilic nodules in mice given PB showed inhibition of growth at confluence, did not grow in soft agar and only four of eight formed tumours in nude mice with a mean average latent period of 181 days. Cells grown from HCC in mice given PB showed a lack of density inhibition of growth, however, they did not grow in soft agar nor did they form tumours in nude mice. A single spontaneous HCC from a control mouse showed a similar growth pattern to HCC cells isolated from mice given PB. Cells from a basophilic nodule, taken from a control untreated mouse grew vigorously in culture and in soft agar and formed tumours in nude mice with a latency of 6 days. None of the cells isolated from control mice or from mice given PB showed evidence of mutations at codon 61 of Ha-ras. These data confirm that there are fundamental differences in the biology of cells grown from tumours that develop in mice under different treatment regimes. These studies also demonstrate the utility of cell culture and molecular biology in addressing the fundamental mechanism of mouse hepatic neoplasia.
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PMID:Growth characteristics and Ha-ras mutations of cell cultures isolated from chemically induced mouse liver tumours. 752 81

SENCAR mice, developed by selective breeding for high susceptibility to skin carcinogenesis by initiation with 7,12-dimethylbenz[a]anthracene and promotion with 12-O-tetradecanoylphorbol-13-acetate (TPA), form squamous papillomas in approximately 20% of animals treated repeatedly with TPA, without chemical initiation. DNA from eight skin tumors produced by a TPA-only protocol and four cell lines derived from these tumors was amplified by polymerase chain reaction and analyzed by discriminative oligonucleotide hybridization using oligomers specific for various c-rasHa gene codon 61 sequences. Five tumors and three cell lines had CAA (wild-type) to CGA mutations. In addition, one tumor had a CAA to CTA mutation, for a total of six of eight tumors having an activating mutation at this codon. Two tumors and one cell line had no codon 61 mutations detectable by this method. Since tumors derived from promotion-only protocols presumably originated from constitutively initiated cells, we examined tumor-free skins of untreated newborn and eight-month-old retired breeders and of 78-88-week-old SENCAR mice of both sexes, which were treated with TPA for 10 weeks starting at age 16-28 weeks and were untreated thereafter. Only the wild-type c-rasHa gene codon 61 sequence was seen, suggesting that the constitutively initiated cell population, if present, is below the limit of detection by this method.
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PMID:SENCAR mouse skin tumors produced by promotion alone have A to G mutations in codon 61 of the c-rasHa gene. 752 83

Foscarnet (phosphonoformic acid) is a pyrophosphate analog that inhibits the replication of human immunodeficiency virus type 1 (HIV-1) in vitro and in patients with AIDS. HIV-1 resistance to foscarnet has not been reported despite long-term foscarnet therapy of AIDS patients with cytomegalovirus disease. We therefore attempted to select foscarnet-resistant HIV-1 in vitro by serial endpoint passage of virus in 400 microM foscarnet. After 13 cycles of passage in MT-2 cells, virus exhibiting > or = 8.5-fold foscarnet resistance was isolated. The reverse transcriptase (RT) from resistant virions exhibited a similar level of foscarnet resistance in enzyme inhibition assays (approximately 10-fold resistance). Foscarnet-resistant virus showed increased susceptibility to 3'-azido-3'-deoxythymidine (90-fold) and to the HIV-1-specific RT inhibitors TIBO R82150 (30-fold) and nevirapine (20-fold). DNA sequence analysis of RT clones from resistant virus revealed the coexistence of two mutations in all clones: Gln-161 to Leu (CAA to CTA) and His-208 to Tyr (CAT to TAT). Sequence analysis of six clinical HIV-1 isolates showing reduced susceptibility to foscarnet revealed the Tyr-208 mutation in two, the Leu-161 mutation in one, and a Trp-88-to-Ser or -Gly mutation in four isolates. Site-specific mutagenesis and production of mutant recombinant viruses demonstrated that the Leu-161, Ser-88, and Tyr-208 mutations reduced HIV-1 susceptibility to foscarnet 10.5-, 4.3-, and 2.4-fold, respectively, in MT-2 cells. In the crystal structure of HIV-1 RT, the Gln-161 residue lies in the alpha E helix beneath the putative deoxynucleoside triphosphate (dNTP) binding site. The Gln-161-to-Leu mutation may affect the structure of the dNTP binding site and its affinity for foscarnet. The location of the Trp-88 residue in the Beta5a strand of HIV-1 RT suggest that the Ser-88 mutation affects template-primer binding, as do several mutations that affect RT susceptibility to nucleoside analogs.
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PMID:Novel mutations in reverse transcriptase of human immunodeficiency virus type 1 reduce susceptibility to foscarnet in laboratory and clinical isolates. 754 60

Dichloroacetic (DCA) and trichloroacetic (TCA) acids, two major by-products formed during chlorine disinfection of drinking water, increase the incidence of tumors in B6C3F1 mice by 6- and 3-fold respectively. In order to understand better the mechanism by which these two compounds induce liver tumors, the incidence and spectrum of mutations in the K- and H-ras proto-oncogenes in these tumors were analyzed. DNA from spontaneous, DCA- and TCA-induced liver tumor from B6C3F1 male mice was evaluated for point mutations in exons 1, 2 and 3 of the two genes by single-stranded conformation polymorphism. Results demonstrated a similar incidence of mutations for exon 2 of H-ras in spontaneous carcinomas (58%), and in carcinomas induced by DCA 3.5 g/l (50%), 1.0 g/l (48%) and TCA 4.5 g/l (45%). Only four showed mutations in the other exons of Hras or in K-ras. Sequence analysis of spontaneous tumor samples with second exon H-ras mutations revealed a change in codon 61 from CAA to AAA in 80% and CAA to CGA in 20% of tumors. In contrast, tumors with H-ras mutations from DCA-treated mice revealed a H-61 change from CAA to AAA in 21% at 3.5 g/l and 16% at 1.0 g/l. CAA to CGA was observed in 50% of tumors from mice given DCA 3.5 or 1.0 g/l, and CAA to CTA was present in 29% and 34% of the two dosage groups respectively. Interestingly, TCA showed the same mutational spectrum as the spontaneous liver tumors. The data indicates that induction of liver carcinoma by DCA and TCA involves activation of the H-ras proto-oncogene at a frequency similar to that observed in spontaneous tumors. However, the mechanism(s) for including hepatocellular carcinoma does not appear to be identical for DCA and TCA.
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PMID:Ras oncogene activation during hepatocarcinogenesis in B6C3F1 male mice by dichloroacetic and trichloroacetic acids. 769 4

To evaluate the presence of precore mutants, serum samples from 25 patients with chronic hepatitis B, HBV-DNA positive (5 HBeAg and 20 anti-HBe positive) were studied. The complete precore-core region of HBV-DNA was directly sequenced after polymerase chain reaction amplification by a fluorescent linear polymerase chain reaction sequencing method. Precore variants were detected in one HBeAg positive and in all 20 anti-HBe positive patients: in 19 cases, G to A at position 1896, with or without the substitution G to A at position 1899, in two cases C to T substitution at position 1817 which also produces a stop codon (CAA to TAA), one accompanied by the mutation G to A at position 1896. The only mutation observed in the patient who was initially HBeAg positive patient was a G to A substitution at position 1899. Consecutive serum samples from a patient with chronic hepatitis B, initially had the simultaneous presence of wild type and variant strains. Elimination of the wild-type strain was associated with reactivation of liver disease. Analysis of the sequences obtained demonstrated the heterogeneity of the hepatitis B virus genome in the precore-core region. These results indicate that the main cause of non-expression of HBeAg in chronic hepatitis B in our country is the substitution of G to A at nucleotide 1896, alone or accompanied by other variants. Fluorescent linear polymerase chain reaction is a fast and sensitive method to study heterogeneity in the precore-core region.
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PMID:Detection of hepatitis B precore mutants by the fluorescent linear polymerase chain reaction sequencing method. 769 56

The Escherichia coli aidB gene is part of the adaptive response to DNA methylation damage. Genes belonging to the adaptive response are positively regulated by the ada gene; the Ada protein acts as a transcriptional activator when methylated in one of its cysteine residues at position 69. Through DNaseI protection assays, we show that methylated Ada (meAda) is able to bind a DNA sequence between 40 and 60 base pairs upstream of the aidB transcriptional startpoint. Binding of meAda is necessary to activate transcription of the adaptive response genes; accordingly, in vitro transcription of aidB is dependent on the presence of meAda. Unmethylated Ada protein shows no protection against DNaseI digestion in the aidB promoter region nor does it promote aidB in vitro transcription. The aidB Ada-binding site shows only weak homology to the proposed consensus sequences for Ada-binding sites in E. coli (AAANNAA and AAAGCGCA) but shares a higher degree of similarity with the Ada-binding regions from other bacterial species, such as Salmonella typhimurium and Bacillus subtilis. Based on the comparison of five different Ada-dependent promoter regions, we suggest that a possible recognition sequence for meAda might be AATnnnnnnG-CAA. Higher concentrations of Ada are required for the binding of aidB than for the ada promoter, suggesting lower affinity of the protein for the aidB Ada-binding site. Common features in the Ada-binding regions of ada and aidB are a high A/T content, the presence of an inverted repeat structure, and their position relative to the transcriptional start site. We propose that these elements, in addition to the proposed recognition sequence, are important for binding of the Ada protein.
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PMID:Transcriptional activation of the Escherichia coli adaptive response gene aidB is mediated by binding of methylated Ada protein. Evidence for a new consensus sequence for Ada-binding sites. 771 36

A 6.4-kb DNA fragment containing the DNA gyrase gyrA and gyrB genes was cloned and sequenced from the quinolone-susceptible Staphylococcus aureus type strain ATCC 12600. An expression plasmid was constructed by inserting the cloned genes into the Escherichia coli-S. aureus shuttle vector pAT19, and deletion plasmids carrying only functional gyrA and gyrB genes were derived from this plasmid. An efficient transformation system for S. aureus RN4220 was established by using these plasmids. Quinolone-resistant mutants of S. aureus RN4220 were isolated by three-step selection with quinolones. The first- and second-step mutants were considered to be transport mutants, and the third-step mutants were divided into five groups with respect to their resistance patterns and transformation results with gyrA and gyrB genes. Sequencing analysis of the resulting mutant gyrase genes showed that they had the following point mutations: group 1, Ser-84 (TCA) to Leu (TTA) in GyrA; group 2, Ser-84 (TCA) to Ala (GCA), Ser-85 (TCT) to Pro (CCT), or Glu-88 (GAA) to Lys (AAA) in GyrA; group 3, Asp-437 (GAC) to Asn (AAC) in GyrB; group 4, Arg-458 (CGA) to Gln (CAA) in GyrB; and group 5, Ser-85 (TCT) to Pro (CCT) in GyrA and Asp-437 (GAC) to Asn (AAC) in GyrB. When the gyrA and/or gyrB mutants were transformed with the wild-type gyrA and/or gyrB plasmids, they became quinolone susceptible, but transformants with the plasmids having the same mutations on the gyrA and/or gyrB genes did not confer susceptibility. These results indicate that mutations in both gyrA and gyrB can be responsible for quinolone resistance in S. aureus.
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PMID:Quinolone resistance mutations in the DNA gyrase gyrA and gyrB genes of Staphylococcus aureus. 781 Oct 12


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