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Biomedical subjects

A Bueno

Publications and source records attributed to A Bueno.

15 recordsLinked to original sources
PubMed1992

Dual functions of CDC6: a yeast protein required for DNA replication also inhibits nuclear division.

The Saccharomyces cerevisiae gene CDC6, whose protein product is required for DNA replication, is transcribed only in late G1 and S phases. We have discovered a critical reason why CDC6 expression is regulated in this fashion. Constitutive CDC6 transcription greatly delayed the initiation of M phase without effecting the G1-S transition or growth rate. This occurred in both fission and budding yeasts. The CDC6-induced M phase delay was dependent on the wee1/mik1 mitotic inhibitor kinases and was greatly accentuated in strains defective for the cdc25/MIH1 mitotic inducer phosphatases, indicating that CDC6 indirectly inhibits activation of the p34cdc2/CDC28 M phase kinase. Thus CDC6 appears to have an important and perhaps unique dual role in S phase, it is first required for the initiation of DNA replication and then actively participates in the suppression of nuclear division.

Base Sequence↗
PubMed1991

A fission yeast B-type cyclin functioning early in the cell cycle.

We have cloned a fission yeast gene, cig1+, encoding a 48 kd product that is most similar to cyclin B proteins. The cig1+ protein has a "cyclin box" approximately 40% identical to B-type cyclins of other species, but lacks the "destruction box" required for proteolysis of mitotic cyclins. Deletion of cig1+ had no observable effect on cell viability or progression through G2 or M phase, but instead caused a marked lag in the progression from G1 to S phase. G1 constituted approximately 70% of the cell cycle in cig1 deletion strains, as compared with less than 10% in cig1+ strains. Constitutive cig1+ overexpression was lethal, causing cessation of growth and arrest in G1. Expression of cig1+ failed to rescue an S. cerevisiae strain lacking CLN Start cyclins. Thus, cig1+ identifies a new class of B-type cyclin acting in G1 or S phase that appears to be functionally distinct from all previously described cyclin proteins.

Amino Acid Sequence↗
PubMed1991

Nucleotide sequence of the exo-1,3-beta-glucanase-encoding gene, EXG1, of the yeast Saccharomyces cerevisiae.

The nucleotide (nt) sequence of the Saccharomyces cerevisiae gene (EXG1) encoding extracellular exo-1,3-beta-glucanases (EXG) I and II was determined. An open reading frame of 1344 bp codes for a 448-amino acid (aa) polypeptide, with a calculated Mr of 51,307, which contains two potential N-glycosylation sites. The EXG1 DNA hybridizes to a 1.7-kb transcript whose 5' end maps to a position 98 bp upstream from the site of initiation of protein synthesis. Comparison of the N-terminal aa sequence deduced from the nt sequence with that of the purified EXGII revealed the existence of an extra 40-aa peptide in the precursor protein containing a Lys-Arg peptidase-processing site at the junction with the mature, extracellular form. The N-terminal region of the putative precursor is a very hydrophobic segment with structural features resembling those of signal peptides of secreted proteins. The Mr of the mature EXG polypeptide deduced from the nt sequence is 46,385. The 5'- and 3'-flanking regions of the EXG1 gene have structural features in common with other yeast genes.

Amino Acid Sequence↗
PubMed1991

cdc25 M-phase inducer.

In this paper, we have described the critical experiments leading to the discovery and analysis of the cdc25 M-phase inducer. We have shown that timing of mitosis is sensitive to the level of cdc25+ expression and that the cellular concentration of p80cdc25 increases as cells approach mitosis. From these observations we conclude that, in S. pombe, rate of accumulation of p80cdc25 plays an important role in determining the timing of mitosis. We postulate that under a given set of conditions, a critical level of p80cdc25 activity is required to undergo mitosis. The actual level that is required can vary depending on ploidy, growth rate, nutritional status of the cell, and perhaps other parameters. These signals may be monitored through the weel pathway leading to tyrosyl phosphorylation of p34cdc2. We have shown that p80cdc25 encodes a phosphate that acts by directly dephosphorylating the Tyr-15 residue of p34cdc2. Our studies strongly indicate that this aspect of the mitotic control network is generally conserved among eukaryotes. It is conceivable, however, that the mode of regulation of cdc25 activity may vary from species to species. Clearly, in S. cerevisiae the cdc25+ homolog, MIH1, in contrast to cdc25+, is not rate-limiting for M-phase onset. It will be important to determine whether the level of cdc25+ homologs in other organisms also oscillates during the cell cycle, or whether their activity is controlled by localization or posttranslational mechanisms, such as phosphorylation. Furthermore, our finding of more than one cdc25+ homolog in a single species suggests an additional level of complexity to the control of M-phase onset by cdc25 in higher eukaryotes that will require further investigation.

Amino Acid Sequence↗
PubMed1991

[Adhesiveness in Neisseria meningitidis. A virulence factor?].

The role of adhesivity as a factor of virulence in cases of N. meningitidis has not yet been established. Unlike other bacteria in which the presence of adhesivity reflects an enhanced virulence, a high capacity of adherence is associated with a low virulence and invasive capacity in cases of meningococcus. In order to gain more insight into the knowledge of this phenomenon we have studied the adhesivity of 109 strains of N. meningitidis to human pharyngeal epithelial cells. Twenty nine out of the 109 strains were isolated from blood or spinal fluid of patients with meningococcal infection (meningitis or septicemia), whereas the remaining 80 strains were obtained from pharyngeal smears of healthy carriers. The adhesivity was measured as the number of meningococci adhered to 50 epithelial cells according to Craven's scale. Strains of healthy carriers showed a greater adhesivity than that of patients (p less than 0.001). The relevance of the pharyngeal area in the evaluation of the adhesive capacity is in accordance with the hypothesis that meningococcal adhesivity decreases when the microorganism crosses the pharyngeal epithelium. The results would support the concept that the virulence of N. meningitidis is related to its adhesiveness.

Bacterial Adhesion↗
PubMed1990

Synthesis and secretion of a Bacillus circulans WL-12 1,3-1,4-beta-D-glucanase in Escherichia coli.

The synthesis and secretion of a 1,3-1,4-beta-D-glucanase were studied in different strains of Escherichia coli transformed with plasmids carrying the Bacillus circulans WL-12 1,3-1,4-beta-D-glucanase structural gene. This gene (named BGC) is contained within a 1.9-kilobase BamHI-HindIII fragment and directs the synthesis in E. coli of an enzyme that specifically degrades lichenan. Only one active form of the enzyme was found when the gene was expressed in different E. coli strains. The electrophoretic pattern of this protein showed a molecular weight that was approximately the same as that of the mature beta-glucanase secreted from B. circulans WL-12, suggesting that the processing of this protein may be similar in both species. As deduced from maxicell experiments, the Bacillus parental promoter directs the synthesis in E. coli. Pulse-chase experiments showed that the protein may be cotranslationally processed.

Bacillus↗
PubMed1986

Methylation of spore DNA in Bacillus coagulans strain 26.

The modification status of DNA throughout the life cycle of Bacillus coagulans strain 26 was analysed by restriction analysis with methylation-sensitive enzymes. A significant fraction of the GATC sequences (dam target) in spore DNA contain N6-methyladenine, a modification that is lacking during the vegetative phase. From the modulation of the modification pattern of GATC sites, the existence of a de novo methylase may be inferred. Spore DNA was more sensitive than vegetative cell DNA to BamHI, HpaI, SalI and XhoI, indicating that the sites for these enzymes are modified during the vegetative growth phase.

Bacillus↗
PubMed1985

[Benign tumors of the esophagus. Esophageal leiomyoma].

Benign neoplasms of the esophagus are rare. The most frequent symptom (75% of the cases) is dysphagia, and a very rare one is dyspnea. When a benign tumor of the esophagus is suspected, a radiological examination is made and the diagnosis confirmed by fibro-esophagoscopy and biopsy. The authors make a summarized review of the benign tumors of the esophagus, and describe a case of esophageal leiomyoma.

Esophageal Neoplasms↗
PubMed1978

Bacterial infections in the newborns.

In the care of 5178 live newborns from October 1971 to October 1974, 252 (4.7%) cases of bacterial infections were diagnosed. Of this number, 131 were full-term and 121 premature newborns. The three most frequent types of infections were gastroenteritis (103 cases = 40.8%), urinary tract infections (77 cases = 30.5%), and septicaemia (51 cases = 20.2%). The three organisms most frequently found were E. coli, Proteus and Enterobacter. The prevalence of gram-negative over gram-posivite germs was very remarkable. In 38 infected newborns the highest IgM levels were achieved at the acme of the illness, and they decreased when the infection subsided.

Bacterial Infections↗
PubMed1977

[Effect on agar on neonatal bilirubin seric levels (author's transl)].

An study on the effect of p.o. agar in neonatal bilirubin seric levels is reported. Two groups of healthy newborns, 33 terms and 22 pre-terms were studied after ingestion of agar and the results compared to those in a similar set of non-agar control groups. Agar ingestion decreased bilirubin levels in term newborns and increased fecal elimination of the pigment (p less than 0.001). p.o. agar had no effect on the levels of serum bilirubin in preterm newborns (p greater than 0.05).

Administration, Oral↗