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J M Lopes

Publications and source records attributed to J M Lopes.

At least 73 records · Page 4Linked to original sources
PubMed1991

Interaction of trans and cis regulatory elements in the INO1 promoter of Saccharomyces cerevisiae.

Electrophoretic mobility shift assays (EMSA) were used to define the regions of the INO1 promoter that interact with factors present in extracts prepared from the yeast, Saccharomyces cerevisae. These experiments identified three different types of protein:DNA complexes that assemble with the INO1 promoter. Formation of one type of complex depended on functional alleles of previously described regulatory genes, INO2 and INO4, that encode positive regulatory factors. Formation of the INO2/INO4-dependent complexes was increased when extracts prepared from cells grown under derepressing conditions (i.e. absence of inositol and choline). A second type of complex was dependent on the OPI1 gene, that encodes a negative regulator. Computer-aided sequence analysis of the promoters of several genes encoding phospholipid biosynthetic enzymes revealed a highly conserved nine basepair element (5'-ATGTGAAAT-3'), designated 'nonamer' motif, that is similar to the octamer motif identified in the promoters of mammalian immunoglobulin genes. The nonamer motif was shown to form a specific complex with a factor, designated nonamer binding factor (NBF). Extracts prepared from Schizosaccharomyces pombe formed a nonamer-specific complex.

Base Sequence↗
PubMed1991

Analysis of sequences in the INO1 promoter that are involved in its regulation by phospholipid precursors.

The promoter region of the highly regulated INO1 structural gene of yeast has been investigated. The major transcription initiation start site (+1) was mapped to a position located five nucleotides upstream of the previously identified initiation codon. The INO1 TATA is located at -116 to -111. The INO1 promoter region was used to construct fusions to the Escherichia coli lacZ gene. All INO1 fusion constructs that retained regulation in response to the phospholipid precursors inositol and choline, contained at least one copy of a nine bp repeated element (consensus, 5'-ATGTG-AAAT-3'). The smallest fragment of the INO1 promoter found to activate and regulate transcription of the fusion gene from a heterologous TATA element was 40 nucleotides in length. This fragment contained one copy of the nine bp repeat and spanned the INO1 promoter region from -259 to -219. However, when an oligonucleotide containing the nine bp repeated sequence was inserted 5' to the CYC1 TATA element, it failed to activate transcription.

Base Sequence↗
PubMed1991

Inositol metabolism in yeasts.

Because of its accessibility to genetic and molecular studies, Sacch. cerevisiae is an attractive organism in which to pursue studies of the complex roles of phosphoinositides and other inositol-containing metabolites. Biochemical studies have clearly demonstrated that PI, PIP, PIP2 and the inositol phosphates derived from them exist in Sacch. cerevisiae. It is clear that they are synthesized and turned over following pathways similar to those described in higher eukaryotes. Recent studies on yeast have also suggested that inositol phospholipids may play roles in complex signalling pathways similar to those detected in animal cells. In addition, inositol has been demonstrated to function in yeast as a global regulator of phospholipid synthesis. This regulation occurs on a transcriptional level and is highly complex. It is not yet known whether similar inositol-mediated regulation of phospholipid synthesis occurs in other eukaryotes.

Inositol↗
PubMed1991

Dermatofibrosarcoma protuberans. A histological and ultrastructural study of 11 cases with emphasis on the study of recurrences and histogenesis.

Eleven cases of dermatofibrosarcoma protuberans (DFSP) (6 male: 5 female; mean age +/- SD: 48.7 +/- 16.1 years) were reviewed in an attempt to correlate the histological and ultrastructural findings with the recurrence pattern of these tumours and to shed light on their histogenesis. Six (54.5%) of the tumours recurred: 3 with a similar appearance to the primary tumours, 2 with fibroblastic malignant fibrohistiocytic pattern (F-MFH), and one with fibrosarcomatous features (F), confirmed ultrastructurally. In one primary tumour with associated F features there were two recurrences. The ultrastructural findings of 6 primary tumours (2 with and 4 without recurrences) showed a predominance of primitive mesenchymal cells. The comparison between the features (sex, age, site, necrosis, mitotic rate size) of recurring DFSP vs DFSP without recurrences did not yield any significant difference. At follow-up (range: 11-108 months) all patients were alive and well. These findings support the assumption that DFSP originates from primitive mesenchymal cells that are able to show, at least, F and F-MFH differentiation, and corroborate the low-grade malignancy of DFSP regardless of their macroscopic, histologic and ultrastructural characteristics.

Adult↗
PubMed1991

Analysis of the use of multiple technologies in neonatal care.

The use of 53 different technologies was studied in 82 patients in a neonatal intensive care unit. Using a coefficient of similarity based on the utilization pattern of these technologies, it was possible to identify five clusters of patients that can be correlated with the primary diagnostic groups and such other variables as birth weight (BW), gestational age, length of stay (LOS), and weight gain. Four interdependent models were identified by multiple regression analysis. The number of different therapeutic technologies applied to these patients can be explained (r = 0.67) by their Apgar scores, gestational age, and an index of severity of illness based on the diagnostic group. The number of different diagnostic technologies used is directly related to the number of therapies delivered (r = 0.63) and, jointly with BW, determines LOS (r = 0.73). Finally, weight gain is explained by LOS and BW (r = 0.65).

Cluster Analysis↗
PubMed1990

Analysis of regulation of the ilvGMEDA operon by using leader-attenuator-galK gene fusions.

Five of the genes for the biosynthesis of isoleucine and valine form the ilvGMEDA operon of Escherichia coli K-12. Expression of the operon responds to changes in the availability of isoleucine, leucine, and valine (ILV). Addition of an excess of all three amino acids results in reduced expression of the operon, whereas limitation for one of the three amino acids causes an increase in expression. The operon is preceded by a leader-attenuator which clearly regulates the increased expression that occurs due to reduced aminoacylation of tRNA. To assess the factors that result in the reduced expression of this operon upon the addition of ILV, a series of plasmids were constructed in which the ilv regulatory region was fused to galK. In response to addition of the amino acids, expression of the galK gene fused to the leader-attenuator decreased five- to sevenfold, instead of the twofold observed for the chromosomal operon. A deletion analysis with these plasmids indicated that the ILV-specific decrease in expression required an intact leader-attenuator but not ilvGp2 or the DNA that precedes this promoter. This conclusion was supported by both S1 nuclease analysis of transcription initiation and determination of galK mRNA levels by RNA-RNA hybridization.

Cloning, Molecular↗
PubMed1989

Physical identification of an internal promoter, ilvAp, in the distal portion of the ilvGMEDA operon.

It has been previously demonstrated that the ilvGMEDA operon is expressed in vivo from the promoters ilvGp2 and ilvEp. An additional internal promoter is identified and designated ilvAp. This internal promoter, which allows independent expression of ilvA, has been analyzed both in vivo and in vitro. Our results indicate that: (1) ilvAp exists in both Escherichia coli K-12 and Salmonella typhimurium, as demonstrated by fusion to the galK reporter gene; (2) ilvAp is located in the distal coding sequence of ilvD; (3) the ilvAp sequences are not identical for these two bacterial species; (4) transcription from ilvAp of E. coli K-12 was demonstrated; (5) expression from ilvAp responds to the availability of oxygen; (6) potential 3' 5'-cyclic AMP receptor protein binding sites exist adjacent to ilvAp.

Base Sequence↗
PubMed1989

Transcriptional polarity enhances the contribution of the internal promoter, ilvEp, in the expression of the ilvGMEDA operon in wild-type Escherichia coli K12.

The ilvG gene of Escherichia coli K12 produces a cryptic peptide as a result of a frameshift mutation located approximately halfway through the coding sequence of the gene. This mutation is polar on expression of the downstream genes (ilvEDA) because transcription terminates within the translationally barren region that results from the mutation. Contrary to this, Salmonella typhimurium produces a full-length functional ilvG protein and is therefore unlikely to manifest this polarity event. E. coli K12 strains with mutations either in the ilvG gene (which restores a full-length protein) or in the rho gene, relieve this polarity suggesting that this event couples transcription and translation in a manner analogous to attenuation. This paper describes experiments designed to determine the molecular nature and location of the polarity event. Most significantly, this work establishes the contribution of the internal promoter (ilvEp, located downstream of the polar site) to the expression of the downstream genes in E. coli K12 wild-type and mutant strains (ilvG) and by extension to the role of this promoter in S. typhimurium. This analysis suggests that ilvEp contributes as much as 90% of ilvEDA expression in wild-type E. coli K12 and only 15% in wild-type S. typhimurium when grown under non-repressing conditions.

Escherichia coli↗
PubMed1987

The complete nucleotide sequence of the ilvGMEDA operon of Escherichia coli K-12.

In this report we present the complete nucleotide sequence of the ilvGMEDA operon of Escherichia coli. This operon contains five genes encoding four of the five enzymes required for the biosynthesis of isoleucine and valine. We identify and describe the coding regions for these five structural genes and the structural and functional features of the flanking and internal regulatory regions of this operon. This new information contributes to a more complete understanding of the overall control of the biosynthesis of isoleucine and valine.

Amino Acid Sequence↗
PubMed1987

Common arterial trunk associated with absence of one atrioventricular connexion.

An unusual case of common arterial trunk is described. The right pulmonary artery is supplied by the ascending trunk and the left pulmonary artery arises via an arterial duct from the left brachiocephalic trunk. Although common arterial trunk can exist with any atrioventricular connexion, the absence of one atrioventricular connexion (tricuspid atresia) is the other rarity of this case.

Heart Atria↗