DNA sequences of two yeast promoter-up mutants

The yeast Saccharomyces cerevisiae has three genetic loci encoding different alcohol dehydrogenase (ADH) isozymes: ADC1, which encodes the classical fermentative isozyme ADHI; ADR2, which encodes the glucose-repressed isozyme ADHII; and ADM, which encodes an ADH isozyme found associated with mitochondria. When yeast are grown on glucose, the ADC1 gene is expressed, and the ADR2 gene repressed. Conversely, growth on a non-fermentable carbon source such as ethanol or glycerol results in derepression of ADR2, and repression of ADC1. The ADC1 and ADR2 genes have been cloned and sequenced, and a number of cis-acting mutations identified that cause constitutive expression of ADR2, and seem to fall into two classes. The most abundant class consists of mutants that cannot be fully derepressed, and do not revert to wild type at a detectable level: these are caused by the insertion of a transposable element into the 5'-flanking region of the gene. The second class of mutants do revert to a glucose-repressed phenotype at a detectable frequency, and when grown on non-fermentable carbon sources derepress ADR2 to levels up to five times those found in wild-type cells. We report here the sequencing of the 5'-flanking regions of two such promoter-up, constitutive ADR2 mutants, in both of which the mutant phenotype is associated with an increase in length of a poly(A) X poly(T) tract 222 base pairs (bp) upstream of the gene.

Deletions and single base pair changes in the yeast mating type locus that prevent homothallic mating type conversions

Several cis-acting mutations that prevent homothallic mating type conversions in Saccharomyces cerevisiae have been examined. Deletions within the mating type (MAT) locus were obtained by selecting for survivors among homothallic MAT alpha cells carrying the rad52 mutation. The survivors were unable to switch mating type, even in RAD+ derivatives. The deletions varied in size from fewer than 50 to more than 750 base pairs. All of the deletions removed a Hha I site at the border between the alpha-specific sequences (Y alpha) and the adjacent Z region. We also examined several spontaneous inc mutations that prevent MAT switching. Two of these mutations were cloned in recombinant DNA plasmids and their sequences were determined. The MAT alpha-inc 3-7 mutation proved to have an altered Hha I site at the Y alpha/Z border, by virtue of a single base pair substitution G . C leads to A . T in the second base pair of the Z region (Z2). Restriction fragment analysis showed that two other independently isolated strains with MAT alpha-inc mutations had altered the same Hha I site. The MAT a-inc 4-28 mutation contains a single base pair substitution C . G leads to T . A at position Z6. A base pair difference at position Z11 in two MATa strains does not affect MATa conversions. We conclude that the region near the Y/Z border is essential for the efficient switching of MAT alleles and constitutes an enzyme recognition site for a specific nucleolytic cleavage of MAT DNA.

Nucleotide sequence of the yeast alcohol dehydrogenase II gene

The complete nucleotide sequence of the glucose-repressed alcohol dehydrogenase II gene (ADR2) from yeast has been established together with its 5'- and 3'-flanking regions. The limits of the gene have been determined by reverse transcriptase sequencing of the 5'-ends and by S1 nuclease mapping of the 3'-ends of the mature ADR2 mRNA. Comparison of the alcohol dehydrogenase I gene (ADC1) sequence (Bennetzen, J. L., and Hall, B.D. (1982) J. Biol. Chem. 257, 3018-3025) with that of ADR2 indicated four regions of sequence conservation in the 5'-flanking DNAs. One of these conserved regions contains the sequence TCAAG which may function as a yeast cap sequence. The coding sequence of ADR2 is 89% homologous with that of ADC1 and exhibits a bias in its codon utilization. Evidence is presented that the intergenic region at the 3'-end of the ADR2 gene is less than 550 base pairs.

Characterization of transposable element-associated mutations that alter yeast alcohol dehydrogenase II expression

Seven cis-dominant, constitutively expressed mutations of the normally glucose-repressible isozyme of alcohol dehydrogenase (ADHII) from the yeast Saccharomyces cerevisiae are caused by insertion of transposable elements from the Ty1 family in front of the ADHII structural gene (ADR2) (V. M. Williamson, E. T. Young, and M. Ciriacy, Cell 23:605-614, 1981). We cloned ADR2 with its associated Ty1 element from five S. cerevisiae strains carrying these mutations. Comparison of the Ty1 elements by heteroduplex studies and restriction enzyme analyses indicated that four were very similar; the fifth, although the same size as the others (about 5.6 kilobases), differed by the presence of two large substitutions of approximately 1 and 2 kilobases. The DNA sequences of the terminal direct repeats (deltas) were very homologous but not identical and were similar to previously reported Ty1 element direct repeats. We determined the 5'-flanking sequences of the ADR2 gene isolated from a wild-type strain and from five Ty1-associated mutations. The 5-base pair target sequence at the site of Ty1 insertion was present at both ends of each Ty1 element. The sites of insertion of the elements were all different and occurred from 125 to 210 base pairs in front of the coding region of ADR2. The 5' end of the major transcript as determined by S1 mapping was the same in wild-type cells and in Ty1-associated constitutive mutants and was approximately 54 base pairs upstream from the coding region. ADR2 transcripts were not detected when a solo delta sequence was present in the 5'-flanking region of this gene.

Steroidal interactions in the regulation of maternal behaviour in virgin female rats: effects of testosterone, dihydrotestosterone, oestradiol, progesterone and the aromatase inhibitor, 1,4,6-androstatriene-3,17-dione

The effects of exposure to concentrations of androgens, oestradiol (OE2) and progesterone similar to those found during pregnancy on the induction of maternal behaviour were investigated in female rats. In the first experiment the effects of testosterone and dihydrotestosterone (DHT) administered in combination with progesterone (using silicone elastomer capsules) on the induction of behavioural responsiveness towards young (crouching, retrieval and grouping of pups) were measured in ovariectomized virgin rats. Hormonally treated animals were exposed to testosterone or DHT from day 1 of treatment to the end of behavioural testing, while progesterone was administered for 10 days (days 3-13). Testing for maternal responsiveness began on day 14 and lasted until day 23. Significant reductions in latencies to show individual aspects of and complete maternal behaviour were found only in animals treated with a combination of testosterone and progesterone (range of mean latencies for showing one aspect of, to complete, maternal behaviour = 1.0-1.4 days). The mean latencies of the other hormonally treated animals ranged from 5 to 6 days and were similar to those of non-hormonally treated control rats. The second experiment examined the possibility that stimulation of maternal behaviour in animals given testosterone and progesterone resulted from the aromatization of testosterone to OE2. Ovariectomized virgin rats were implanted with capsules containing testosterone and other with the aromatase inhibitor, 1,4,6-androstatriene-3,17-dione (ATD) on day 1, and with progesterone capsules on day 3. Progesterone capsules were removed on day 13 and behavioural testing commenced on day 14. Treatment with testosterone and progesterone failed to stimulate maternal behaviour in rats treated with ATD. In a third study ovariectomized virgin rats were implanted with OE2 on day 1 and progesterone on day 3. The progesterone implants were removed on day 13 and testing began on day 14. Significant reductions in latencies to show all aspects of maternal behaviour were found in these rats. In a final study progesterone capsules remained in OE2- and progesterone-treated rats from day 3 until the completion of behavioural testing. The presence of progesterone implants throughout the test period (days 14-23) blocked the rapid onset of maternal responsiveness induced by removal of progesterone on day 13 shown in rats treated with OE2 plus progesterone in experiment 3. These data suggest that during gestation testosterone, through its conversion to OE2, synergizes with progesterone to help stimulate the development of the capacity of the female animal to respond maternally to young, a capacity unmasked by withdrawal of progesterone before parturition.

Reversible dissociation of wheat germ ribosomal subunits: cation-dependent equilibria and thermodynamic parameters

The influence of magnesium ion concentration upon the equilibrium between the wheat germ ribosome and its subunits has been studied by light scattering. The curves obtained for ribosome dissociation and subunit reassociation were identical and were independent of the origin and direction of the magnesium ion titration, suggesting that the wheat germ ribosomes are behaving as a homogeneous population equivalent to Escherichia coli type A ribosomes. Increasing K+ concentrations in the presence of Mg2+ favored ribosome dissociation. Polyamines favored subunit reassociation, with 0.1 mM spermine acting as effectively as 1 mM spermidine. Thermodynamic parameters have been determined from the temperature-dependent equilibria and have been compared to those of E. coli type A ribosomes. The association of the 40S and 60S subunits is exothermic. At 1.5 mM Mg2+ and 100 mM K+, the entropy term is negative, favoring ribosome dissociation, and contributes less to the free energy than the enthalpy term. The determination of these thermodynamic parameters was based on molecular weights of 1.2 x 10(6) and 2.3 x 10(6) for the 40S and 60S subunits, respectively, calculated from laser light scattering data.

Purification and characterization of a ribosome dissociation factor (eukaryotic initiation factor 6) from wheat germ

A wheat germ ribosome dissociation factor, eukaryotic initiation factor 6 (eIF-6), has been purified almost to homogeneity from the 25 to 40% ammonium sulfate fraction of the postribosomal supernatant. This dissociation factor is distinct from initiation factor eIF-3 and its chromatographic properties permit its separation from the known wheat germ initiation factors. Under certain conditions, eIF-6 stimulates the incorporation of amino acids into polypeptides in a partially fractionated wheat germ cell-free system. The eight-step purification procedure developed includes chromatography on DEAE-cellulose, phosphocellulose, Sephadex G-75, and hydroxyapatite and yields a dissociation factor more than 80% pure. The purified factor is composed of a single polypeptide chain with a molecular weight of approximately 23,000 as determined by gel filtration chromatography and by sodium dodecyl sulfate-polyacrylamide gel electrophoresis. It is an acidic protein which is heat labile and is inactivated by treatment with N-ethylmaleimide. The dissociation factor is much more effective in preventing the reassociation of 40 S and 60 S ribosomal subunits than in directly dissociating 80 S ribosomes. Like Escherichia coli IF-3, about 10 pmol of the dissociation factor are required to dissociate 1 pmol of ribosomes.

Identification of a wheat germ ribosome dissociation factor distinct from initiation factor eIF-3

A ribosome dissociation factor(s) has been partially purified from extracts of wheat germ. This factor can be detected by its ability to prevent the reassociation of ribosomal subunits when the magnesium concentration is raised from 1 mM to 5 mN. The majority of the dissociation factor activity is found in the postribosomal supernatant of the cell and can be precipitated between 0 and 40% ammonium sulfate. Chromatography of this material on DEAE-cellulose yields a fraction which contains both the dissociation factor activity and initiation factor eLF-3. However, the majority of the dissociation factor activity can be readily separated from eIF-3 by chromatography on phosphocellulose. The dissociation factor appears to be distinct from any of the othe known wheat germ initiation factors.

Isolation and structure of pimaydolide, a cyclodepsipeptide metabolite of Pithomyces maydicus

A new metabolite has been isolated from cultures of Pithomyces maydicus. Evidence is presented that suggests its structure is cyclo(L-2-oxy-3-methylbutyryl-D-valyl-D-leucyl-L-2-oxy-4-methylvaleryl-L-2-oxy-3-methylbutyryl-L-N-methylleucyl), 1.

Enniatin production by Fusarium sambucinum: primary, secondary, and unitary metabolism

Fusarium sambucinum liquid surface cultures on semi-defined medium with glucose as carbon source passed through well-defined phases corresponding to trophophase, idiophase (enniatin production), and a degenerative phase. All the glucose was consumed by day 6, at which time the mycelial dry weight had reached only half its maximum. When glucose was replaced by lactose, there was no separation of trophophase and idiophase. Enniatin production, dry weight, and sugar and nitrogen consumption were in approximate balance throughout the growth period (25 days), after which slow degeneration began. The term 'unitary metabolism' is proposed for this type of unphased behaviour. Unitary metabolism may approximate more closely to that occurring under natural conditions than does the metabolic phase separation observed when rapidly utilized carbon sources are used in laboratory cultures.

Permeability of human erythrocytes to isonicotinic acid hydrazide and its metabolites

Intra- and extracellular concentrations of isonicotinic acid hydrazide equalized rapidly in suspensions of washed human or rabbit erythrocytes incubated with the drug in Tyrode solution at pH 7.4, 37 °C. Thus, contrary to an earlier report, erythrocytes are not impermeable to this compound. Of its known human metabolites, only the hydrazones with pyruvic and α-ketoglutaric acids were excluded from human erythrocytes.

Evidence for biosynthetical equivalence of the epimeric isoleucine residues in angolide

Pithomyces sacchari was grown on media containing L-valine. Instead of the metabolite angolide (cyclo-L-α-hydroxyisovaleryl1-erythro-L-isoleucyl2-L-α-hydroxyisovaleryl3-threo-D-isoleucyl4), synthesized on un-supplemented media, it produced a mixture with very similar physical properties. Acid hydrolysis liberated erythro-L- and threo-D-isoleucines (1:1), and DL-valine in amounts proportional to the exogenous valine concentration; L-α-hydroxyisovaleric acid was the only other component. Radioactivity from L-valine-U-14C was incorporated without dilution into valine, and with extensive dilution into the hydroxy acid.Partial fractionation of the mixture was achieved by column chromatography. Mass spectra of two fractions, containing different proportions of valine, were compared with the spectrum of angolide. A simple mathematical treatment showed that the fractions contained angolide, its divaline homologue, and a homologue with only one isoleucine replaced by valine. This must be a 1: 1 mixture of the two possible isomers, since any deviation from this ratio is inconsistent with the analytical results. It follows that the erythro-L- and the threo-D-isoleucine residues of angolide are equivalent with respect to their replacement by valine. It is inferred that angolide biosynthesis involves a cyclic intermediate containing both amino acid residues in the L configuration.

Isoniazid acetylation rates (phenotypes) of patients being treated for tuberculosis

Isoniazid therapy could be used more rationally if patients' isoniazid acetylation rates were known. To explore the clinical usefulness of a recently described simple method for acetylator phenotyping, acetylated and free isoniazid were measured semiquantitatively in morning urine specimens from sanatorium in-patients being treated with the drug. The distribution of acetylisoniazid: isoniazid ratios was bimodal. The ratios thus identify rapid and slow acetylators of isoniazid, without disturbing their routine or their therapy. Ratios measured in samples from control subjects who had received a single dose of isoniazid did not discriminate between these phenotypes, and urine from diabetic patients gave false reactions.

Simple method for determining isoniazid acetylator phenotype

Methods have been developed for estimating acetylisoniazid and isoniazid in urine without a spectrophotometer. In experiments with volunteers the ratio of acetylisoniazid to isoniazid in urine samples collected the morning after three spaced oral doses each of 100 mg. was bimodally distributed.

Blockage by gibberellic Acid of phytochrome effects on growth, auxin responses, and flavonoid synthesis in etiolated pea internodes

Red light inhibits the growth of etiolated pea internodes, causes a shift toward higher indoleacetic acid (IAA) concentrations in the IAA dose-response curve of excised sections, and promotes the synthesis in intact internodes of kaempferol-3-triglucoside. Gibberellic acid (GA(3)) prevents all 3 effects, the first effect substantially and the last 2 completely. This suggests GA(3) blockage of an early or basic event initiated by the active form of phytochrome. The red light-induced shift in the IAA dose-response curve of excised sections is consistent with a light-induced increase in the activity of an IAA destruction system, since the magnitude of the red light inhibition varied with IAA concentration. The red light and GA(3) effects on growth and on flavonoid synthesis are consistent with the view that phytochrome may control growth by regulating the synthesis of phenolic compounds which act as cofactors in an IAA-oxidase system. GA(3) reversal of the red light-induced shift in the IAA dose-response curve involves both growth promotion and inhibition by GA(3) at different IAA concentrations and this, together with the GA(3) reversal of light-induced flavonoid synthesis, supports the suggested regulatory role of phenolic compounds in growth.

Comparative analysis of phytochrome-mediated growth responses in internodes of dwarf and tall pea plants

Responses of dark-grown pea seedlings of a dwarf (Progress No. 9) and a tall (Alaska) cultivar to red light have been compared 24 hours after irradiation. Identical percentage inhibition of elongation in 10-mm sub-apical segments of intact third internodes, identical dose-response curves and similar reversal of the inhibition by far-red light were observed. The time courses of the growth inhibition were quantitatively dissimilar in that seedlings of Alaska showed greater inhibition soon after light treatment, but greater recovery at later stages.Small varietal differences in phytochrome concentrations in comparable parts of the apical region correlate with early varietal differences in the growth response. Seedlings of Progress showed considerable far-red reversal of the red-light effect even with an extended time lapse between red and far-red irradiations, while decay of far-red reversibility was comparatively rapid in Alaska seedlings. It is concluded that there is no difference in energies required to activate the phytochrome system in the two varieties, but that the Pfr form of phytochrome probably remains stable and active in Progress but decays rapidly in Alaska seedlings.