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T G Cooper

Publications and source records attributed to T G Cooper.

At least 217 records · Page 12Linked to original sources
PubMed1987

Ubiquitous upstream repression sequences control activation of the inducible arginase gene in yeast.

Expression of the yeast arginase gene (CAR1) responds to both induction and nitrogen catabolite repression. Regulation is mediated through sequences that both positively and negatively modulate CAR1 transcription. A short sequence, 5'-TAGCCGCCGAGGG-3', possessing characteristics of a repressor binding site, plays a central role in the induction process. A fragment containing this upstream repression sequence (URS1) repressed gene expression when placed either 5' or 3' to the upstream activation sequences of the heterologous gene CYC1. Action of the URS and its cognate repressor was overcome by CAR1 induction when the URS was situated cis to the CAR1 flanking sequences. This was not observed, however, when it was situated downstream of a heterologous CYC1 upstream activation sequence indicating that URS function is specifically neutralized by cis-acting elements associated with CAR1 induction. Searches of sequences in various gene banks revealed that URS1-like sequences occur ubiquitously in genetic regulatory regions including those of bacteriophage lambda, yeast, mammalian, and viral genes. In a significant number of cases the sequence is contained in a region associated with negative control of yeast gene regulation. These data suggest the URS identified in this work is a generic repressor target site that apparently has been conserved during the evolution of transcriptional regulatory systems.

Arginase↗
PubMed1987

Allantoin transport in Saccharomyces cerevisiae is regulated by two induction systems.

We show that the allantoin transport system of Saccharomyces cerevisiae responds to two induction systems, one mediated by allophanate or its analog oxalurate and the other mediated by allantoin or its analog hydantoin acetate. The effects of the two inducers were additive in strain M85. Like other allantoin pathway genes, oxalurate-mediated induction of allantoin transport required a functional DAL81 gene product. Hydantoin acetate-mediated induction of the system, on the other hand, occurred normally in dal81 mutants. This suggests that induction was not only mediated by two separate inducers, but also involved different regulatory proteins. Induction is probably a transcriptionally regulated process, because addition of hydantoin acetate or oxalurate to the culture medium increased the steady-state levels of mRNA encoded by a gene required for allantoin transport (DAL4).

Allantoin↗
PubMed1987

Regulation of allantoate transport in wild-type and mutant strains of Saccharomyces cerevisiae.

Accumulation of intracellular allantoin and allantoate is mediated by two distinct active transport systems in Saccharomyces cerevisiae. Allantoin transport (DAL4 gene) is inducible, while allantoate uptake is constitutive (it occurs at full levels in the absence of any allantoate-related compounds from the culture medium). Both systems appear to be sensitive to nitrogen catabolite repression, feedback inhibition, and trans-inhibition. Mutants (dal5) that lack allantoate transport have been isolated. These strains also exhibit a 60% loss of allantoin transport capability. Conversely, dal4 mutants previously described are unable to transport allantoin and exhibit a 50% loss of allantoate transport. We interpret the pleiotropic behavior of the dal4 and dal5 mutations as deriving from a functional interaction between elements of the two transport systems.

Allantoin↗
PubMed1987

Ureidosuccinate is transported by the allantoate transport system in Saccharomyces cerevisiae.

The regulatory characteristics exhibited by ureidosuccinate transport in Saccharomyces cerevisiae led us to hypothesize that this biosynthetic intermediate was transported via the degradative allantoate transport system. The hypothesis was verified by the finding that neither dal5 nor urep1 mutant strains could transport allantoate or ureidosuccinate. Mutations in the two loci were tightly linked and failed to complement one another, suggesting that they were allelic. The use of a common transport system for accumulation of both biosynthetic and degradative metabolites explains the paradoxical characteristics observed for control of ureidosuccinate and allantoate transport.

Aspartic Acid↗
PubMed1987

Transcriptional regulation of the DAL5 gene in Saccharomyces cerevisiae.

We demonstrate that the DAL5 gene, encoding a necessary component of the allantoate transport system, is constitutively expressed in Saccharomyces cerevisiae. Its relatively high basal level of expression did not increase further upon addition of allantoin pathway intermediates. However, steady-state DAL5 mRNA levels dropped precipitously when a repressive nitrogen source was provided. These control characteristics of DAL5 expression make this gene a good model with which to unravel the mechanism of nitrogen catabolite repression. Its particular advantage relative to other potentially useful genes derives from its lack of control by induction and hence the complicating effects of inducer exclusion.

Allantoin↗
PubMed1986

A sensitive bioluminescence assay for myo-inositol.

A specific, sensitive bioluminescence assay for myo-inositol is described employing myo-inositol dehydrogenase linked to a commercial NADH bioluminescence kit. Optimum conditions providing a linear response over 4 orders of magnitude are presented with reproducibility of 6% CV and a sensitivity of 1 pmol. The assay is suitable for the measurement of inositol at low concentrations or in small volumes.

Inositol↗
PubMed1986

Characteristics of the transport of carnitine into the cauda epididymidis of the rat as ascertained by luminal perfusion in vitro.

An in vitro luminal perfusion technique was used to monitor the transepithelial movement of [3H]L-carnitine into the cauda epididymal lumen of rats. Movement of the volume marker [14C]inulin into the lumen was limited while the transport of [3H]L-carnitine was saturable and was dependent on respiratory energy. The transport of L-carnitine (50 microM) was significantly inhibited by 500 microM D-carnitine, palmitoyl L-carnitine and deoxycarnitine but not by trimethylammonium iodide, trimethyl phosphate, acetyl-L-carnitine, choline, betaine, gamma-aminobutyric acid or DL-carnitinamide. The Kt (116 microM) and Vmax (0.1 nmol/30 min/cm) for the carriers were calculated from the present data and as the Kt is about twice the normal plasma concentration of carnitine, the rate of transport by the pump is presumed to be limited by the plasma concentration.

Animals↗
PubMed1986

Induction and repression of the urea amidolyase gene in Saccharomyces cerevisiae.

The DUR1,2 gene from Saccharomyces cerevisiae has been isolated on recombinant plasmids along with all DNA between the DUR1,2 and MET8 loci. DUR1,2 was found to encode a 5.7-kilobase transcript, which is consistent with our earlier suggestion that the DUR1 and DUR2 loci are two domains of a single multifunctional gene. Steady-state levels of the DUR1,2 transcript responded to induction and nitrogen catabolite repression in the same way as urea amidolyase activity. dal81 mutants (grown with inducer) contained barely detectable amounts of DUR1,2 RNA, whereas dal80 mutants (grown without inducer) contained the same amount as a wild-type induced culture. These observations support our earlier hypothesis that DUR1,2 is transcriptionally regulated, with control being mediated by the DAL80 and DAL81 gene products. We cloned the DUR1,2-Oh mutation and found it to be a Ty insertion near sequences required for complementation of dur1,2 mutations. The ROAM phenotype of the DUR1,2-Oh mutation is sharply different from that of cis-dominant, DUR80 mutations, which enhance DUR1,2 expression but do not affect the normal control pattern of the gene. There is evidence that DUR80 mutations may also be Ty insertions, which generate phenotypes that are different from those in DUR1,2-Oh mutations.

Carbon-Nitrogen Ligases↗
PubMed1986

Transport of carnitine by the epididymis of the cynomolgus macaque (Macaca fascicularis).

Unravelled tubules from the monkey caput and cauda epididymidis were perfused through the lumen in vitro during immersion in an organ bath kept at scrotal temperature and containing [3H]carnitine and [14C]inulin. The specific transport of carnitine from the bath to the lumen was constant for 4 h and reached a steady-state value of about 90 pmol/30 min per cm perfused length in the cauda and about 30 pmol/30 min/cm in the caput. These regional variations in carnitine transport differ from those found in the rat epididymis but may be relevant to human epididymal physiology.

Animals↗
PubMed1985

Point mutation generates constitutive expression of an inducible eukaryotic gene.

We describe the analysis of two cis-dominant mutations that result in constitutive expression of the inducible CAR1 gene from yeast. One mutation results from insertion of a Ty element just upstream from the point where CAR1-specific transcription begins. The other mutation is a C-to-G transversion at position -153. Isolation of this point mutation, outside of the transcribed region of CAR1, suggests that expression of this gene is regulated at transcription. It also demonstrates the feasibility and usefulness of analyzing the regulatory sequences of eukaryotic genes on a nucleotide-by-nucleotide basis.

Alleles↗
PubMed1985

Prevention of hypo-osmotic swelling by detergents provides clues to the membrane structure of rat sperm.

The proportion of sperm from the caput epididymidis of the rat that swelled in hypo-osmotic media was reduced in a dose-dependent manner by detergents, with relative effectiveness as follows: CTAB greater than Digitonin greater than Hyamine 10-X greater than SDS greater than Triton X-100 greater than Deoxycholate. Polymyxin was a poor lytic agent, possibly because anionic lipids are in the inner leaflet of the membrane. Less digitonin was needed to lyse mature sperm from the distal cauda epididymidis, suggesting that there is less cholesterol in their membranes.

Animals↗
PubMed1985

Identification of the ureidoglycolate hydrolase gene in the DAL gene cluster of Saccharomyces cerevisiae.

This report describes the isolation of the genes encoding allantoicase (DAL2) and ureidoglycolate hydrolase (DAL3), which are components of the large DAL gene cluster on the right arm of chromosome IX of Saccharomyces cerevisiae. During this work a new gene (DAL7) was identified and found to be regulated in the manner expected for an allantoin pathway gene. Its expression was (i) induced by allophanate, (ii) sensitive to nitrogen catabolite repression, and (iii) responsive to mutation of the DAL80 and DAL81 loci, which have previously been shown to regulate the allantoin degradation system. Hybridization probes generated from these cloned genes were used to analyze expression of the allantoin pathway genes in wild-type and mutant cells grown under a variety of physiological conditions. When comparison was possible, the patterns of mRNA and enzyme levels observed in various strains and physiological conditions were very similar, suggesting that the system is predominantly regulated at the level of gene expression. Although all of the genes seem to be controlled by a common mechanism, their detailed patterns of expression were, at the same time, highly individual and diverse.

Allantoin↗
PubMed1985

Luminal secretion of myo-inositol by the rat epididymis perfused in vitro.

A technique for perfusing the lumen of rat epididymal tubules maintained in vitro showed that [3H]inulin was largely excluded from the lumen of unravelled tubules from the cauda and tubules from the corpus if the connective tissue capsule was removed. The preparation transported [3H]inositol from the bath fluid for 3 h against a concentration gradient in both regions with activity rising (16-29% of bath fluid values) in the cauda and reaching a plateau (18%) in the corpus epididymidis. HPLC showed that radioactivity was solely associated with inositol and its movement to the lumen was reduced by raising inositol in the bath fluid from 50 microM (plasma levels) to 10 mM, but not affected by reducing the glucose concentration in the bath fluid or introducing physiological concentrations of inositol (30 mM) into the lumen. Secretion into the caudal lumen of unlabelled inositol measured by g.l.c. was maintained for 3 h at concentrations (300 microM) greater than those in the bath fluid and was not reduced when glucose or inositol were removed from the bath. In contrast, glucose was only detectable in the lumen when it was present in the bathing medium, reaching 1% of this concentration. Radioactivity appeared in the epididymal lumen reaching a plateau (19% of bath fluid values) in the corpus and cauda when [3H]glucose was added to the bath fluid, but no radiolabelled inositol was found in the lumen. We conclude that epididymal tissue is a major source of secreted inositol.

Animals↗
PubMed1984

Tau, sigma, and delta. A family of repeated elements in yeast.

We report here the isolation and structure of a new repeated DNA element, tau. This element, from Saccharomyces cerevisiae, is 371 base pairs long and is flanked on either end by the same invertedly repeated sequence found at the ends of some Ty and sigma elements in yeast, copia elements in Drosophila and spleen necrosis virus. The tau inverted repeats are themselves flanked by a 5-base pair directly repeated genomic sequence that is present only once in a cognate tau-allele. These structural characteristics, the presence of multiple copies of tau in the genome, and the isolation of tau+ and tau- allelic pairs suggest that tau may be capable of transposition either alone or in association with some larger element. Detailed sequence analysis of the tau, sigma, and delta elements revealed that all three contain significant regions of homology, suggesting that they are probably members of a single family derived from a common progenitor.

Base Composition↗
PubMed1984

tau, a repeated DNA sequence in yeast.

We have found a 371-base-pair (bp) repeated DNA element, tau, in Saccharomyces cerevisiae. The ends of tau are composed of a 5-bp inverted repeat, similar in sequence to those reported for the Ty, sigma, copia, and spleen necrosis virus elements. These inverted repeats are flanked by 5-bp direct repeats of a target sequence that occurs only once in an allele that lacks the tau element. This overall structure is characteristic of transposable elements. Like sigma, tau elements have been found (in both orientations) closely associated with tRNA genes (409 and 198 bp from the 5' end, respectively). It is noteworthy that one representative of tau was isolated in a concentric insertion of tau, delta, and sigma.

Base Composition↗
PubMed1984

Location of the genes that control induction of the allantoin-degrading enzymes in Saccharomyces cerevisiae.

In an effort to understand the regulation of allantoin degradation in Saccharomyces cerevisiae, we isolated two classes of mutants, each defective in the induction process associated with production of the pathway enzymes. Mutation at one locus (DAL80) results in constitutive expression of the genes involved in allantoin catabolism. Mutation at the second locus (DAL-81) results in the loss of ability to induce these enzymes. This report describes genetic data indicating that the DAL80 and DAL81 loci are situated approximately 13 cM from the centromere on the right arm of chromosome XI and 9 cM proximal to the DAL1 locus on chromosome IX, respectively.

Allantoin↗