Biomedical subjects

M Company

Publications and source records attributed to M Company.

18 recordsLinked to original sources

PubMed2005

A foodborne outbreak of Salmonella infection due to overproduction of egg-containing foods for a festival.

A large outbreak of gastroenteritis occurred in Catalonia in June 2002 with 1435 cases and 117 hospitalizations. Consumption of a hard pastry with vanilla cream was strongly associated with illness. Stool samples from cases and food-handlers were analysed. The premises of the food manufacturer were inspected and food samples were taken for microbiological analysis. Salmonella serotype Enteriditis was isolated from 154 cases, three food-handlers and nine food samples. Outbreak-associated strains showed a coincident phage type, antibiotype and pulse-field gel electrophoresis pattern. Inadequate handling of foods containing eggs occurred because the establishment exceeded its safe food production capacity to meet demand for the pastry, which was consumed on the day of a traditional festival. Excessive production of foods for holidays or special events represents a potential public health threat.

Adolescent↗

PubMed2002

Factors promoting colonization by legionellae in residential water distribution systems: an environmental case-control survey.

As part of a case-control study of community-acquired Legionnaires' disease, several factors related to residential water distribution systems and public drinking water systems were studied in the homes of 124 patients with community-acquired Legionnaire's disease and in the homes of 354 controls. The presence of water reservoirs and hot water tanks was studied in residential systems. Factors such as deficient chlorine levels, pipe repairs and other work, water flow interruptions, the use of alternative water sources, inadequate cleaning operations in public water reservoirs, and the position of the home within the public network (and whether this location constituted an endpoint) were studied in public water supply systems. Levels of legionellae in domestic water samples were also measured. Although the use of water reservoirs and hot water tanks promotes colonization by legionellae in residential systems, none of the variables studied seems to increase the incidence of community-acquired Legionnaires' disease.

Case-Control Studies↗

PubMed1998

The DEAH-box protein PRP22 is an ATPase that mediates ATP-dependent mRNA release from the spliceosome and unwinds RNA duplexes.

Of the proteins required for pre-mRNA splicing, at least four, the DEAH-box proteins, are closely related due to the presence of a central 'RNA helicase-like' region, and extended homology through a large portion of the protein. A major unresolved question is the function of these proteins. Indirect evidence suggests that several of these proteins are catalysts for important structural rearrangements in the spliceosome. However, the mechanism for the proposed alterations is presently unknown. We present evidence that PRP22, a DEAH-box protein required for mRNA release from the spliceosome, unwinds RNA duplexes in a concentration- and ATP-dependent manner. This demonstrates that PRP22 can modify RNA structure directly. We also show that the PRP22-dependent release of mRNA from the spliceosome is an ATP-dependent process and that recombinant PRP22 is an ATPase. Non-hydrolyzable ATP analogs did not substitute for ATP in the RNA-unwinding reaction, suggesting that ATP hydrolysis is required for this reaction. Specific mutation of a putative ATP phosphate-binding motif in the recombinant protein eliminated the ATPase and RNA-unwinding capacity. Significantly, these data suggest that the DEAH-box proteins act directly on RNA substrates within the spliceosome.

Adenosine Triphosphatases↗

PubMed1995

Specificity of Prp24 binding to RNA: a role for Prp24 in the dynamic interaction of U4 and U6 snRNAs.

Prp24 was previously isolated as a suppressor of a cold-sensitive U4 mutation and is required for at least the first step of splicing in vitro. Our investigation of the in vitro RNA binding properties of the purified Prp24 protein shows that it binds preferentially to the U4/U6 hybrid snRNAs compared to other snRNAs. The interaction between Prp24 and the U4/U6 hybrid appears to involve two regions in the RNA: the 39-57 region of U6 and stem II of the U4/U6 hybrid. Interestingly, some U4 mutations, which destabilize stem II, increase the affinity of Prp24 for the U4/U6 RNAs compared to the wild type. This suggests that the binding of Prp24 to the U4/U6 RNAs may involve some destabilization of the RNA duplex. We also found that Prp24 can stimulate the annealing of U4 and U6, suggesting that Prp24 participates in both the formation and disassembly of the U4/U6 hybrid during splicing.

Base Sequence↗

PubMed1991

Requirement of the RNA helicase-like protein PRP22 for release of messenger RNA from spliceosomes.

The product of the yeast PRP22 gene acts late in the splicing of yeast pre-messenger RNA, mediating the release of the spliced mRNA from the spliceosome. The predicted PRP22 protein sequence shares extensive homology with that of PRP2 and PRP16 proteins, which are also involved in nuclear pre-mRNA splicing. The homologous region contains sequence elements characteristic of several demonstrated or putative ATP-dependent RNA helicases. A putative RNA-binding motif originally identified in bacterial ribosomal protein S1 and Escherichia coli polynucleotide phosphorylase has also been found in PRP22.

Adenosine Triphosphate↗

PubMed1991

Kinetics of the reaction between 5,5'-dithiobis[2-nitrobenzoic acid] and the sulphydryl group in Zn(2+)-dependent beta-lactamase II.

The kinetics of the reaction of the thiol residue in Zn(2+)-dependent beta-lactamase II with 5,5'-dithiobis[2-nitrobenzoic acid], and the concomitant inactivation revealed that both events take place at the same rate. The inactivation could not be reverted by incubation with Zn2+ or by using a substrate concentration about eight times the Km of the enzyme. EDTA incubation also produced inactivation of the enzyme, although it was reverted by increasing the substrate concentration in the assay. A dual role is proposed for Zn2+ in beta-lactamase. The kinetic analysis of the thiol modification and the concomitant inactivation is in agreement with previous reports on the implication of the metal ion in catalysis. A role in stabilizing the native structure of the enzyme is also suggested.

Bacillus↗

PubMed1991

Degradation of beta-lactam antibiotics in the presence of Zn2+ and 2-amino-2-hydroxymethylpropane-1,3-diol (Tris). A hypothetical non-enzymic model of beta-lactamases.

The system composed of 2-amino-2-hydroxymethylpropane-1,3-diol (Tris) and Zn2+ catalyses the degradation of cephalosporins. The beta-lactam opening fits to a first-order process, with a constant directly proportional to the zinc ion concentration. The pH and Tris concentration dependency displayed by the first-order constant, as well as the nature of the degradation products point to a mechanism that can be considered as an extension of that proposed for the benzylpenicillin degradation. The mechanism proposed here, and the values of the kinetic constants calculated, as compared with those of beta-lactamases, lead to the conclusion that the Tris-Zn2+ system simulates the catalytic action of the serine beta-lactamases rather than the action of the Zn(2+)-dependent type of enzymes.

Anti-Bacterial Agents↗

PubMed1991

Comparative study of various hydrogen ion buffers to assay Zn(2+)-dependent beta-lactamases.

The low Zn2+ complex formation constants, the capacity to degrade penicillin G in combination with Zn2+, and UV absorbance make 4-(2-hydroxyethyl)-1-piperazineethanesulfonic acid, 3-[N-tris(hydroxymethyl)methylamino]-2-hydroxypropanesulfonic acid, 1,3-bis[tris(hydroxymethyl)methylamino]propane, and 1,4-piperazinediethanesulfonic acid convenient buffers to study Zn(2+)-dependent beta-lactamases.

Bacillus cereus↗

PubMed1990

A yeast-Escherichia coli shuttle vector containing the M13 origin of replication.

A yeast-Escherichia coli shuttle vector containing the M13 origin of replication has been constructed. This vector allows selection and replication in both Saccharomyces cerevisiae and E. coli, as well as single-stranded packaging from E. coli upon infection with a helper phage. The presence of a polylinker with various unique restriction sites facilitates the cloning of desired genes.

Base Sequence↗

PubMed1989

Isolation and characterization of pre-mRNA splicing mutants of Saccharomyces cerevisiae.

In this study we report the isolation of temperature-sensitive mutants that affect pre-mRNA splicing. A bank of approximately 1000 temperature-sensitive Saccharomyces cerevisiae strains was generated and screened on RNA gel blots by hybridization with an actin intron probe. We isolated 16 mutants defining 11 new complementation groups prp(rna)17-prp(rna)27 with four phenotypic classes of mutants and 21 mutants in the prp2-prp11 complementation groups (formerly rna2-rna11). The majority of the complementation groups share a phenotype of pre-mRNA accumulation, seen in all of the prp(rna)2-prp(rna)11 mutants. Three novel classes of mutants were isolated in this study. One class, consisting of two complementation groups, exhibits an accumulation of the lariat intermediate of splicing, with no change in the levels of pre-mRNA. The second class, also represented by two complementation groups, shows an accumulation of the intron released after splicing. The third novel class, comprising one complementation group, accumulates both pre-mRNA and the released intron. All mutants isolated were recessive for the splicing phenotype. Only 2 of the 11 complementation groups, although recessive, were not temperature sensitive. This study, together with previous isolation of the prp(rna)2-prp(rna)11 groups and the spliceosomal snRNAs, puts at least 26 gene products involved directly or indirectly in pre-mRNA splicing.

Alleles↗

PubMed1988

A stopped-flow assay for glycogen phosphorylase appropriate to measure catalytic activity at high enzyme concentrations.

Glycogen phosphorylase (EC 2.4.1.1) may be assayed in the glycogen degradation direction by a continuous spectrophotometric method. The formation of glucose 1-phosphate from glycogen and phosphate produces a controlled change of pH which can be measured by the changes in absorbance of phenol red added to the system. The procedure may be conveniently applied to a stopped-flow spectrophotometer to measure the rate of the reaction. Therefore the activity of the enzyme may be determined at low conventional concentrations and, by the same technique, at high enzyme concentrations approaching those supposed to exist in vivo.

Animals↗

PubMed1988

A Ty1 cell-type-specific regulatory sequence is a recognition element for a constitutive binding factor.

Ty transposable-element insertion mutations of Saccharomyces cerevisiae can cause cell-type-dependent activation of adjacent-gene expression. Several cis-acting regulatory regions within Ty1 are responsible for the effect of Ty1 on adjacent-gene expression. One of these is the block II sequence that was defined by its homology to mammalian enhancers and to the yeast a1-alpha 2 control site. Tandem copies of a 57-base-pair region encompassing block II caused an additive increase in expression of the CYC7 reporter gene in the absence of other Ty1 sequences. The activation of gene expression by the multiple repeats was abolished in a/alpha diploid cells. A specific complex between a constitutive factor in whole-cell extracts and the DNA regulatory element was observed. The protein-binding site for the constitutive factor coincided with the block II element. Base-pair substitutions within the binding site abolished the ability of the block II element to function as a component of the Ty1 activator and to form the factor-DNA complex. The correlation between complex formation and reporter gene expression indicates that factor binding to the cis-acting element is essential for this element to function as a component of the Ty1 activator.

Base Sequence↗

PubMed1988

Identification of a Ty1 regulatory sequence responsive to STE7 and STE12.

Ty1 activation of gene expression observed in haploid cell types of Saccharomyces cerevisiae requires the STE7 and STE12 gene products. An activator sequence within Ty1 that is responsive to these two regulators has been defined. Complex formation between a factor in whole-cell extracts and the DNA regulatory element showed the same dependence on the STE7 and STE12 gene products as did reporter gene expression. Base pair substitutions within the binding site abolished the ability to form the factor-DNA complex and to activate gene expression. The correlation between complex formation and reporter gene expression indicates that factor binding to the cis-acting element is essential for gene activation. Because the predicted protein for the STE7 gene product is homologous to protein kinases, we suggest that protein phosphorylation may directly or indirectly regulate formation of this DNA-protein complex.

Base Sequence↗

PubMed1987

Ty1 sequence with enhancer and mating-type-dependent regulatory activities.

Some insertion mutations in Saccharomyces cerevisiae activate the expression of adjacent structural genes. The CYC7-H2 mutation is a Ty1 insertion 5' to the iso-2-cytochrome c coding region of CYC7. The Ty1 insertion causes a 20-fold increase in CYC7 expression in a and alpha haploid cell types of S. cerevisiae. This activation is repressed in the a/alpha diploid cell type. Previous computer analysis of the CYC7-H2 Ty1 activator region identified two related sequences with homology both to mammalian enhancers and to a yeast a/alpha control site. A 112-base-pair (bp) DNA fragment encompassing one of these blocks of homology functioned as one component of the Ty1 activator. A 28-bp synthetic oligonucleotide with the wild-type homology block sequence was also functional. A single base pair mutation within the enhancer core of the synthetic 28-bp regulatory element reduced its activation ability to near background amounts. In addition, the 112-bp Ty1 fragment by itself functioned as a target for repression of adjacent gene expression in a/alpha diploid cells.

Amino Acid Sequence↗

PubMed1987

Cell-type-dependent gene activation by yeast transposon Ty1 involves multiple regulatory determinants.

Ty transposable element insertion mutations of Saccharomyces cerevisiae can cause cell-type-dependent activation of adjacent gene expression. Several cis-acting regulatory regions within Ty1 that are responsible for these effects were identified. A 211-base-pair (bp) region functions as an activator. This region includes the so-called U5 domain of delta and 145 bp of adjacent epsilon sequences. Unlike activation by the intact Ty1, activation by the 211-bp Ty1 subfragment is cell-type independent. The presence of a 112-bp fragment from a more distal region of Ty1 confers cell-type specificity to the activator. The 112-bp fragment includes sequences with homology to mammalian enhancers and to a yeast a/alpha control site. In addition, Ty1 regions that exert negative effects on gene expression were identified. These results demonstrate that the Ty1 transcriptional control region consists of multiple components with distinct regulatory functions.

Cell Differentiation↗

PubMed1986

Transcriptional analysis of Ty1 deletion and inversion derivatives at CYC7.

One class of Ty insertion mutation in Saccharomyces cerevisiae activates expression of adjacent structural genes. The CYC7-H2 mutation, in which a Ty1 element is inserted 5' to the iso-2-cytochrome c coding region of CYC7, causes a 20-fold increase in CYC7 expression. Deletion analysis of CYC7-H2 has shown that distal regions of the Ty1 element are not essential for the transcriptional activation at CYC7. In this report, we have analyzed Ty1 and CYC7 RNA from two CYC7-H2 deletion derivative genes to determine whether a direct correlation exists between transcription of Ty1 and transcription of the adjacent gene. Assuming that all Ty1 elements in the genome are transcribed equally, amounts of CYC7-H2 deletion derivative Ty1 RNA were found to be at least fivefold lower than the amount estimated for the average Ty1 element. These same Ty1 deletion derivatives caused a 20-fold increase in adjacent CYC7 expression. This finding suggests that the mechanism by which Ty1 activates adjacent gene expression does not require normal levels of Ty1 transcription. Two inversion derivatives of the CYC7-H2 Ty1 have also been analyzed. These derivatives did not produce any iso-2-cytochrome c or any normal CYC7 mRNA. Instead they were found to produce a Tyl-CYC7 fusion RNA. Consistent with our findings on CYC7-H2 Ty1 transcription, the amount of the fusion RNA was very low. In addition, the Ty1 inversion derivatives produced a new RNA that mapped to sequences upstream from the inverted Ty1 segment. Similar to Ty1 insertions that activate transcription, the new RNA was found to be transcribed away from Ty1.

Alleles↗

PubMed1986

An anomalous Ty1 structure attributed to an error in reverse transcription.

We have determined the nucleotide sequence of both delta elements of a Ty1 transposon inserted near the CYC7 gene in the Saccharomyces cerevisiae CYC7-H2 mutant. The upstream delta element in this Ty1 has an unusual inverted repeat structure that may have been formed by an error during reverse transcription.

Base Composition↗

PubMed1985

Activation regions in a yeast transposon have homology to mating type control sequences and to mammalian enhancers.

The DNA sequence of the Ty1 activating region from the CYC7-H2 mutant of Saccharomyces cerevisiae is presented. Analysis of the data revealed the presence of four simian virus 40-type enhancer core sequences. Two of the Ty1 enhancer cores are contiguous with sequences also homologous to the diploid control site at MAT alpha. We postulate that these two Ty1 regions of approximately equal to 30 base pairs are regulatory blocks, and we have analyzed deletions to ascertain whether they are necessary for effects of Ty1 on adjacent gene expression. We found that activation is lost when a restriction fragment encompassing both postulated regulatory blocks is deleted. Deletion of restriction fragments that remove only one of the two regulatory blocks has little or no effect on Ty1 activating ability in haploid yeast cells or on repression of this function in diploid yeast cells. Because the most significant internal homologies in the restriction fragments analyzed are the putative regulatory blocks, these observations suggest that enhancer-like sequences are involved in cell-type control of Ty1 effects on gene expression.

Base Sequence↗