14-3-3 (Bmh) proteins inhibit transcription activation by Adr1 through direct binding to its regulatory domain

14-3-3 proteins, known as Bmh in yeast, are ubiquitous, highly conserved proteins that function as adaptors in signal transduction pathways by binding to phosphorylated proteins to activate, inactivate, or sequester their substrates. Bmh proteins have an important role in glucose repression by binding to Reg1, the regulatory subunit of Glc7, a protein phosphatase that inactivates the AMP-activated protein kinase Snf1. We describe here another role for Bmh in glucose repression. We show that Bmh binds to the Snf1-dependent transcription factor Adr1 and inhibits its transcriptional activity. Bmh binds within the regulatory domain of Adr1 between amino acids 215 and 260, the location of mutant ADR1(c) alleles that deregulate Adr1 activity. This provides the first explanation for the phenotype resulting from these mutations. Bmh inhibits Gal4-Adr1 fusion protein activity by binding to the Ser230 region and blocking the function of a nearby cryptic activating region. ADR1(c) alleles, or the inactivation of Bmh, relieve the inhibition and Snf1 dependence of this activating region, indicating that the phosphorylation of Ser230 and Bmh are important for the inactivation of Gal4-Adr1. The Bmh binding domain is conserved in orthologs of Adr1, suggesting that it acquired an important biological function before the whole-genome duplication of the ancestor of S. cerevisiae.

Evidence that human epididymal protein ARP plays a role in gamete fusion through complementary sites on the surface of the human egg

Human epididymal sperm protein ARP, a member of the cysteine-rich secretory proteins (CRISP) family, exhibits significant homology with rat epididymal protein DE, a candidate molecule for mediating sperm-egg fusion in rodents. The aim of this study was to investigate the involvement of ARP in human gamete fusion. Sequential extraction of proteins from ejaculated human sperm revealed the existence of a population of ARP that is tightly associated with the sperm surface and thus, potentially capable of participating in gamete interaction. Exposure of capacitated human sperm to a polyclonal antibody against recombinant ARP (anti-ARP) produced a significant and concentration-dependent inhibition in the ability of human sperm to penetrate zona-free hamster eggs. This inhibition was not due to a deleterious effect on the gametes because anti-ARP affected neither sperm viability or motility, nor egg penetrability. The antibody did not inhibit the occurrence of spontaneous or Ca(2+) ionophore-induced acrosome reaction, nor did it inhibit the ability of sperm to bind to the oolema, supporting a specific inhibition of the antibody at the sperm-egg fusion level. As a relevant evidence for a role of ARP in gamete fusion, the existence of complementary sites for this protein on the surface of human eggs was investigated. Experiments in which zona-free human oocytes discarded from in vitro fertilization programs were exposed to ARP, fixed, and subjected to indirect immunofluorescence revealed the presence of specific ARP-binding sites on the entire surface of the human egg, in agreement with the fusogenic properties of the human oolema. Together, these results strongly support the participation of ARP in the sperm-egg fusion process, suggesting that this protein would be the functional homologue of DE in humans.

Evidence for a Graves' disease susceptibility locus at chromosome Xp11 in a United Kingdom population

Graves' disease (GD), which has a strong female preponderance (female/male ratio, >5:1), is inherited as a complex genetic trait. Loci for GD have started to be defined using genome-wide approaches for genetic linkage. To date, 3 loci have been confirmed in at least 2 cohorts of GD patients, the strongest effect being at the cytotoxic T lymphocyte antigen-4 (CTLA-4) locus on chromosome 2q33 in our population. Two other loci for GD have recently been proposed, but not confirmed, on chromosomes Xq21 (GD3) and 14q31 (GD1). We studied a cohort of 75 sibling pairs with GD from the United Kingdom for linkage to 12 markers over a 83-cM region of the X chromosome and for 8 markers over a 36-cM region of 14q31-q33. A peak multipoint nonparametric linkage score of 2.21 (P = 0.014) was found at marker DXS8083 on Xp11, which increased to a nonparametric linkage score of 3.18 (P = 0.001) in data that had been conditioned for allele sharing at the CTLA-4 locus under an epistatic model. There was no evidence to support linkage of GD to Xq21.33-q22 (GD3) or at the 14q31-q33 (GD1) region in our population. A locus with a moderate contribution to GD susceptibility (lambda(s) = 1.4) is likely to exist in the Xp11 region, but we are unable to confirm that the GD1 or the GD3 regions contain major susceptibility loci in our United Kingdom GD population.

Evidence for a new Graves disease susceptibility locus at chromosome 18q21

Graves disease (GD) is a common autoimmune thyroid disorder that is inherited as a complex multigenic trait. By using a single microsatellite marker at each locus, we screened the type 1 diabetes loci IDDM4, IDDM5, IDDM6, IDDM8, and IDDM10 and the fucosyltransferase-2 locus for linkage in sib pairs with GD. This showed a two-point nonparametric linkage (NPL) score of 1.57 (P=.06) at the IDDM6 marker D18S41, but NPL scores were <1.0 at the other five loci. Thus, the investigation of the IDDM6 locus was extended by genotyping 11 microsatellite markers spanning 48 cM across chromosome 18q12-q22 in 81 sib pairs affected with autoimmune thyroid disease (AITD). Multipoint analysis, designating all AITD sib pairs as affected, showed a peak NPL score of 3.46 (P=.0003), at the marker D18S487. Designation of only GD cases as affected (74 sib pairs) showed a peak NPL score of 3.09 (P=.001). Linkage to this region has been demonstrated in type 1 diabetes (IDDM6), rheumatoid arthritis, and systemic lupus erythematosus, which suggests that this locus may have a role in several forms of autoimmunity.

Evolution of a glucose-regulated ADH gene in the genus Saccharomyces

To determine when a glucose-repressed alcohol dehydrogenase isozyme and its regulatory gene, ADR1, arose during evolution, we surveyed species of the genus Saccharomyces for glucose-repressed ADH isozymes and for ADR1 homologues. Glucose-repressed ADH isozymes were present in all species of Saccharomyces sensu strictu and also in Saccharomyces kluyveri, the most distant member of the Saccharomyces clade. We cloned and characterized ADH promoters from S. bayanus, S. douglasii, and S. kluyveri. The ADH promoters from S. bayanus and S. douglasii had conserved sequences, including upstream regulatory elements, and an extended polydA tract. The expression of a reporter gene driven by the S. bayanus promoter was glucose-repressed and dependent on the major activator of transcription, ADR1, when it was introduced into S. cerevisiae. One S. kluyveri promoter was also glucose-repressed and ADR1-dependent in S. cerevisiae. The other S. kluyveri ADH promoter was expressed constitutively and was ADR1-independent. Although showing little sequence conservation with the S. cerevisiae ADH2 promoter, the glucose-repressed S. kluyveri promoter contains numerous potential binding sites for Adr1. The glucose-repressed ADH from S. kluyveri is a mitochondrial isozyme most closely related to S. cerevisiae ADHIII. ADR1 homologues from S. douglasii and S. paradoxus contain a trinucleotide repeat encoding polyAsn that is lacking in S. cerevisiae and S. bayanus. No ADR1 homologue could be detected in S. kluyveri, suggesting that the potential for Adr1 regulation may have arisen first, before ADR1 evolved.

Trinucleotide repeats are clustered in regulatory genes in Saccharomyces cerevisiae

The genome of Saccharomyces cerevisiae contains numerous unstable microsatellite sequences. Mononucleotide and dinucleotide repeats are rarely found in ORFs, and when present in an ORF are frequently located in an intron or at the C terminus of the protein, suggesting that their instability is deleterious to gene function. DNA trinucleotide repeats (TNRs) are found at a higher-than-expected frequency within ORFs, and the amino acids encoded by the TNRs represent a biased set. TNRs are rarely conserved between genes with related sequences, suggesting high instability or a recent origin. The genes in which TNRs are most frequently found are related to cellular regulation. The protein structural database is notably lacking in proteins containing amino acid tracts, suggesting that they are not located in structured regions of a protein but are rather located between domains. This conclusion is consistent with the location of amino acid tracts in two protein families. The preferred location of TNRs within the ORFs of genes related to cellular regulation together with their instability suggest that TNRs could have an important role in speciation. Specifically, TNRs could serve as hot spots for recombination leading to domain swapping, or mutation of TNRs could allow rapid evolution of new domains of protein structure.

Association analysis of the cytotoxic T lymphocyte antigen-4 (CTLA-4) and autoimmune regulator-1 (AIRE-1) genes in sporadic autoimmune Addison's disease

Although autoimmune Addison's disease (AAD) may occur as a component of the monogenic autoimmune polyendocrinopathy type 1 syndrome (APS1), it is most commonly found as an isolated disorder or associated with the autoimmune polyendocrinopathy type 2 syndrome (APS2). It is likely that sporadic (non-APS1) AAD is inherited as a complex trait; however, apart from the major histocompatibility complex, the susceptibility genes remain unknown. We have examined polymorphisms at two non-major histocompatibility complex candidate susceptibility loci in sporadic (non-APS1) AAD: the cytotoxic T lymphocyte antigen-4 (CTLA-4) gene and the autoimmune regulator (AIRE-1) gene. DNA samples from AAD subjects (n = 90) and local controls (n = 144 for CTLA-4; n = 576 for AIRE-1) were analyzed for the CTLA-4A/G polymorphism in exon 1 of the CTLA-4 gene and for the common mutant AIRE-1 allele (964de113) in United Kingdom subjects with APS1, by using the restriction enzymes Bst7II and BsrBI, respectively. There was an association of the G allele at CTLA-4A/G in AAD subjects (P = 0.008 vs. controls), which was stronger in subjects with AAD as a component of APS2 than in subjects with isolated AAD. In contrast, the mutant AIRE-1 964del13 allele was carried in one each of the 576 (0.2%) control subjects and the 90 (1.1%) AAD subjects as a heterozygote (P = 0.254, not significant), suggesting that this common AIRE-1 gene abnormality does not have a major role in sporadic (non-APS1) AAD.

An accessory DNA binding motif in the zinc finger protein Adr1 assists stable binding to DNA and can be replaced by a third finger

The DNA binding domain of Adr1, the protein derived from alcohol dehydrogenase regulatory gene 1, is unusual for zinc finger proteins in that it consists of two classical Cys2His2 zinc fingers and an amino-terminal proximal accessory region termed PAR. PAR is unstructured in the free protein and becomes structured in the DNA-bound form. We investigated the role of PAR in DNA binding using molecular and biochemical approaches, and its importance for activation in vivo, using Adr1-dependent reporter genes. PAR was unimportant for DNA binding when a third finger was added to Adr1, and its importance was diminished but not eliminated by mutations in finger two that increased DNA binding affinity. The kinetic rate constants for three Adr1 proteins containing or lacking PAR were determined by surface plasmon resonance. PAR increased the on rate and decreased the off rate for specific DNA sites for Adr1 containing wild-type fingers one and two. Surprisingly, PAR had no significant effect on the kinetic rate constants when a third finger was present, or when single-stranded DNA was used as the substrate for DNA binding. A mutant form of Adr1-F1F2 in which finger 2 makes three base-specific contacts with DNA had a higher affinity for DNA than Adr1 containing three fingers, yet the mutant protein still depended on PAR for optimal binding affinity. The ability to activate transcription in vivo was correlated with a low dissociation rate, suggesting that stabilizing an activator at the promoter might be rate-limiting for transcription in vivo. PAR may have evolved to lend additional stability to DNA-Adr1 complexes encompassing short binding sites. In addition, PAR may have a role in transcription at a step after DNA binding since deletion of PAR from Adr1 with three fingers decreased activation in vivo but had no effect on DNA binding kinetics.

Post-translational regulation of Adr1 activity is mediated by its DNA binding domain

ADR1 encodes a transcriptional activator that regulates genes involved in carbon source utilization in Saccharomyces cerevisiae. ADR1 is itself repressed by glucose, but the significance of this repression for regulating target genes is not known. To test if the reduction in Adr1 levels contributes to glucose repression of ADH2 expression, we generated yeast strains in which the level of Adr1 produced during growth in glucose-containing medium is similar to that present in wild-type cells grown in the absence of glucose. In these Adr1-overproducing strains, ADH2 expression remained tightly repressed, and UAS1, the element in the ADH2 promoter that binds Adr1, was sufficient to maintain glucose repression. Post-translational modification of Adr1 activity is implicated in repression, since ADH2 derepression occurred in the absence of de novo protein synthesis. The N-terminal 172 amino acids of Adr1, containing the DNA binding and nuclear localization domains, fused to the Herpesvirus VP16-encoded transcription activation domain, conferred regulated expression at UAS1. Nuclear localization of an Adr1-GFP fusion protein was not glucose-regulated, suggesting that the DNA binding domain of Adr1 is sufficient to confer regulated expression on target genes. A Gal4-Adr1 fusion protein was unable to confer glucose repression at GAL4-dependent promoters, suggesting that regulation mediated by ADR1 is specific to UAS1.

Functional analysis of the yeast Glc7-binding protein Reg1 identifies a protein phosphatase type 1-binding motif as essential for repression of ADH2 expression

In Saccharomyces cerevisiae, the protein phosphatase type 1 (PP1)-binding protein Reg1 is required to maintain complete repression of ADH2 expression during growth on glucose. Surprisingly, however, mutant forms of the yeast PP1 homologue Glc7, which are unable to repress expression of another glucose-regulated gene, SUC2, fully repressed ADH2. Constitutive ADH2 expression in reg1 mutant cells did require Snf1 protein kinase activity like constitutive SUC2 expression and was inhibited by unregulated cyclic AMP-dependent protein kinase activity like ADH2 expression in derepressed cells. To further elucidate the functional role of Reg1 in repressing ADH2 expression, deletions scanning the entire length of the protein were analyzed. Only the central region of the protein containing the putative PP1-binding sequence RHIHF was found to be indispensable for repression. Introduction of the I466M F468A substitutions into this sequence rendered Reg1 almost nonfunctional. Deletion of the central region or the double substitution prevented Reg1 from significantly interacting with Glc7 in two-hybrid analyses. Previous experimental evidence had indicated that Reg1 might target Glc7 to nuclear substrates such as the Snf1 kinase complex. Subcellular localization of a fully functional Reg1-green fluorescent protein fusion, however, indicated that Reg1 is cytoplasmic and excluded from the nucleus independently of the carbon source. When the level of Adr1 was modestly elevated, ADH2 expression was no longer fully repressed in glc7 mutant cells, providing the first direct evidence that Glc7 can repress ADH2 expression. These results suggest that the Reg1-Glc7 phosphatase is a cytoplasmic component of the machinery responsible for returning Snf1 kinase activity to its basal level and reestablishing glucose repression. This implies that the activated form of the Snf1 kinase complex must cycle between the nucleus and the cytoplasm.

The cytotoxic T lymphocyte antigen-4 is a major Graves' disease locus

Graves' disease (GD) is an autoimmune thyroid disorder that is inherited as a complex trait. We have genotyped 77 affected sib-pairs with autoimmune thyroid disease for eight polymorphic markers spanning the cytotoxic T lymphocyte antigen-4 ( CTLA-4 ) region of chromosome 2q31-q33, and for five markers spanning the major histocompatibility complex ( MHC ) region of chromosome 6p21. Non-parametric analysis showed linkage of GD to the CTLA-4 region with a peak non-parametric linkage (NPL) score of 3.43 ( P = 0.0004) at the marker D2S117. The proportion of affected full-sibs sharing zero alleles (z0) reached a minimum of 0.113 close to D2S117, giving a locus-specific lambdas for this region of 2.2. Families with brother-sister sib-pairs showed a peak NPL of 3.46 ( P = 0.0003, lambdas > 10) at D2S117, compared with 2.00 ( P = 0.02, lambdas = 1.9) in the families with only affected females, suggesting a stronger influence in families with affected males. Association between GD and the G allele of the Thr17Ala polymorphism within the CTLA-4 gene ( CTLA4A/G ) was observed using unaffected sib controls ( P = 0.005). Lesser evidence for linkage was found at the MHC locus, with a peak NPL score of 1.95 ( P = 0.026), between the markers D6S273 and TNFalpha. We demonstrate that the CTLA-4 locus (lambdas = 2.2) and the MHC locus (lambdas = 1.6) together confer approximately 50% of the inherited susceptibility to GD disease in our population.

Characterization of a p53-related activation domain in Adr1p that is sufficient for ADR1-dependent gene expression

The yeast transcriptional activator Adr1p controls expression of the glucose-repressible alcohol dehydrogenase gene (ADH2), genes involved in glycerol metabolism, and genes required for peroxisome biogenesis and function. Previous data suggested that promoter-specific activation domains might contribute to expression of the different types of ADR1-dependent genes. By using gene fusions encoding the Gal4p DNA binding domain and portions of Adr1p, we identified a single, strong acidic activation domain spanning amino acids 420-462 of Adr1p. Both acidic and hydrophobic amino acids within this activation domain were important for its function. The critical hydrophobic residues are in a motif previously identified in p53 and related acidic activators. A mini-Adr1 protein consisting of the DNA binding domain of Adr1p fused to this 42-residue activation domain carried out all of the known functions of wild-type ADR1. It conferred stringent glucose repression on the ADH2 locus and on UAS1-containing reporter genes. The putative inhibitory region of Adr1p encompassing the protein kinase A phosphorylation site at Ser-230 is thus not essential for glucose repression mediated by ADR1. Mini-ADR1 allowed efficient derepression of gene expression. In addition it complemented an ADR1-null allele for growth on glycerol and oleate media, indicating efficient activation of genes required for glycerol metabolism and peroxisome biogenesis. Thus, a single activation domain can activate all ADR1-dependent promoters.

Meiotic inheritance of functional Gal80S gene product in Saccharomyces cerevisiae

Transcription factors inherited during meiosis play a crucial role directing subsequent gene activity. Factors of maternal origin have been shown to influence the pattern of early zygotic transcription during Drosophila and Xenopus embryogenesis. Nevertheless, little is known regarding the meiotic inheritance of the vast majority of transcription factors. In the case of yeast meiosis, for example, it is not yet known whether any of the multitude of transcription factors expressed in the diploid are transmitted to haploid spores in functional form. Here we use a GAL1-STE4 reporter whose activity is detectable in single living cells to identify a transcription factor inherited during sporulation in Saccharomyces cerevisiae. We show that functional Gal80S repressor is meiotically inherited at levels reflecting its expression in the diploid parent.

Cyclic AMP-dependent protein kinase inhibits ADH2 expression in part by decreasing expression of the transcription factor gene ADR1

In Saccharomyces cerevisiae, the unregulated cyclic AMP-dependent protein kinase (cAPK) activity of bcy1 mutant cells inhibits expression of the glucose-repressible ADH2 gene. The transcription factor Adr1p is thought to be the primary target of cAPK. Here we demonstrate that the decreased abundance of Adr1p in bcy1 mutant cells contributes to the inhibition of ADH2 expression. Activation of ADH2 transcription was blocked in bcy1 mutant cells, and UAS1, the Adr1p binding site in the ADH2 promoter, was sufficient to mediate this effect. Concurrent with this loss of transcriptional activation was an up to 30-fold reduction in the level of Adr1p. Mutating the strong cAPK phosphorylation site at serine 230 did not suppress this effect. Analysis of ADR1 mRNA levels and ADR1-lacZ expression suggested that decreased ADR1 transcription was responsible for the reduced protein level. In contrast to the ADH2 promoter, however, deletion analysis suggested that cAPK does not act through a discrete DNA element in the ADR1 promoter. The amount of Adr1p found in bcy1 mutant cells should have been sufficient to support 23% of the wild-type level of ADH2 expression. Since no ADH2 expression was detectable in bcy1 mutant cells, cAPK must also act by other mechanisms. Overexpression of Adr1p only partially restored ADH2 expression, indicating that some of these mechanisms may impinge upon events at or subsequent to the ADR1-dependent step in ADH2 transcriptional activation.

The incidence of diabetes mellitus in an English community: a 20-year follow-up of the Whickham Survey

The original Whickham Survey documented the prevalence of diabetes and lipid disorders in a sample of 2779 adults aged 18 years and over, which matched the British population structure. The aim of the 20-year follow-up study was to determine the incidence and natural history of diabetes. Outcomes in terms of morbidity and mortality at follow-up were determined in over 97% of the original population. Ninety-four subjects had been identified and treated for diabetes since the first survey, including 17 subjects identified as having a fasting plasma glucose > or = 7.8 mmol l-1 at follow-up. The incidence of diabetes for the total population was 2.2 1000-1 year-1 (95% confidence interval 1.8, 2.6). The risk factors identified at first survey were corrected for age, cut-off at the 95 centile and entered into a log linear model. Those which strongly predicted development of diabetes in the total population were fasting blood glucose (odds ratio (OR) (with 95% confidence intervals) = 2.3 (1.5, 3.5)) and body mass index (OR = 2.2 (1.5, 3.3)) in men, and fasting blood glucose (OR = 2.6 (1.7, 4.1)) and fasting serum triglyceride (OR = 2.8 (1.8, 4.4)) in women. A logit model has enabled the calculation of the probability of developing diabetes 20 years later. It was the characteristics of becoming older such as obesity, hypertriglyceridaemia, and raised fasting blood glucose, rather than age itself, which were associated with the development of diabetes.

Isolation and identification of genes activating UAS2-dependent ADH2 expression in Saccharomyces cerevisiae

Two cis-acting elements have been identified that act synergistically to regulate expression of the glucose-repressed alcohol dehydrogenase 2 (ADH2) gene. UAS1 is bound by the trans-activator Adr1p. UAS2 is thought to be the binding site for an unidentified regulatory protein. A genetic selection based on a UAS2-dependent ADH2 reporter was devised to isolate genes capable of activating UAS2-dependent transcription. One set of UAS2-dependent genes contained SPT6/CRE2/SSN20. Multicopy SPT6 caused improper expression of chromosomal ADH2. A second set of UAS2-dependent clones contained a previously uncharacterized open reading frame designated MEU1 (Multicopy Enhancer of UAS2). A frame shift mutation in MEU1 abolished its ability to activate UAS2-dependent gene expression. Multicopy MEU1 expression suppressed the constitutive ADH2 expression caused by cre2-1. Disruption of MEU1 reduced endogenous ADH2 expression about twofold but had no effect on cell viability or growth. No homologues of MEU1 were identified by low-stringency Southern hybridization of yeast genomic DNA, and no significant homologues were found in the sequence data bases. A MEU1/beta-gal fusion protein was not localized to a particular region of the cell. MEU1 is linked to PPR1 on chromosome XII.

The development of ischemic heart disease in relation to autoimmune thyroid disease in a 20-year follow-up study of an English community

The original Whickham Survey documented risk factors for cardiovascular disease and the prevalence of thyroid disorders in a sample of 2779 adults that closely matched the British population. A 20-year follow-up study has determined outcomes in terms of morbidity and mortality from ischemic heart disease in over 97% of the original survey population. Analysis of deaths from all causes and from ischemic heart disease showed no association with antithyroid antibody status identified at first survey. A multiple logistic regression using the development of ischemic heart disease in the total population at follow-up as the dependent variable found that the significant predictor variables for men were age, cholesterol, mean arterial blood pressure, smoking history, and skinfold thickness index. For women only age, cholesterol, and mean arterial blood pressure were significant. The presence of autoimmune thyroid disease, as defined by either hypothyroidism, positive antithyroid antibodies, or raised serum thyrotropin at first survey, was not significant. A retrospective cohort study of a subsample of women identified at first survey with positive antithyroid antibodies or raised serum thyrotropin and closely matched controls found no significant association with mortality or development of ischemic heart disease. There is no evidence from this study to suggest that evidence of autoimmune thyroid disease identified 20 years ago is associated with an increased risk of ischemic heart disease.

A single amino acid substitution in zinc finger 2 of Adr1p changes its binding specificity at two positions in UAS1

The two zinc fingers of the yeast transcription factor Adr1p recognize the 6 bp sequence TTG GAG site in which the first finger, a His-X3-His finger, recognizes the G-rich triplet (GAG) and the second zinc finger, a His-X4-His finger, recognizes the T-rich sequence (TTG). Mutations were introduced into the alpha-helical region of the second finger and the resultant mutant proteins were analyzed for DNA binding affinity and specificity in vitro and in vivo. Substituting His for Leu in the third position (+3) of the helix created a new binding specificity at two positions in the binding site. The mutant with His replacing Leu146(L146H) bound with high affinity to GGG GGG and with low affinity to TTG GGG. The single substitution at position +3 in the helix had the same effect on DNA binding specificity as substitution of the whole helix of the second finger with the helix of finger one. Changing Asp145 to Ala in the presence of His146 changed the apparent binding site of finger 2 to GT/CG. The L146H mutant zinc finger protein had the same binding specificity in vivo as in vitro. Changing the spacing between the His residues that ligand zinc in the second finger from four to three, the spacing found in the first finger of Adr1p and Zif268, did not alter the specificity or affinity of the wild-type or mutant protein.

Synergistic activation of ADH2 expression is sensitive to upstream activation sequence 2 (UAS2) orientation, copy number and UAS1-UAS2 helical phasing

The alcohol dehydrogenase 2 (ADH2) gene of Saccharomyces cerevisiae is under stringent glucose repression. Two cis-acting upstream activation sequences (UAS) that function synergistically in the derepression of ADH2 gene expression have been identified. UAS1 is the binding site for the transcriptional regulator Adr1p. UAS2 has been shown to be important for ADH2 expression and confers glucose-regulated, ADR1-independent activity to a heterologous reporter gene. An analysis of point mutations within UAS2, in the context of the entire ADH2 upstream regulatory region, showed that the specific sequence of UAS2 is important for efficient derepression of ADH2, as would be expected if UAS2 were the binding site for a transcriptional regulatory protein. In the context of the ADH2 upstream regulatory region, including UAS1, working in concert with the ADH2 basal promoter elements, UAS2-dependent gene activation was dependent on orientation, copy number, and helix phase. Multimerization of UAS2, or its presence in reversed orientation, resulted in a decrease in ADH2 expression. In contrast, UAS2-dependent expression of a reporter gene containing the ADH2 basal promoter and coding sequence was enhanced by multimerization of UAS2 and was independent of UAS2 orientation. The reduced expression caused by multimerization of UAS2 in the native promoter was observed only in the presence of ADR1. Inhibition of UAS2-dependent gene expression by Adr1p was also observed with a UAS2-dependent ADH2 reporter gene. This inhibition increased with ADR1 copy number and required the DNA-binding activity of Adr1p. Specific but low-affinity binding of Adr1p to UAS2 in vitro was demonstrated, suggesting that the inhibition of UAS2-dependent gene expression observed in vivo could be a direct effect due to Adr1p binding to UAS2.

Intrapulmonary shunting causing hypoxaemia in a case of carcinoid syndrome

A case of metastatic carcinoid syndrome with hypoxaemia is described. The hypoxaemia appeared to be due to intrapulmonary shunting. There was improvement in resting and exercise arterial oxygen saturations following chemotherapy with streptozotocin and 5-fluorouracil. This was followed by a decrease in the tumour bulk which may have led to a reduction in the secretion of the vasodilator products responsible for shunting. Some features of this case suggest that the hypoxaemia might have been due to dilatation of precapillary and capillary vessels of the pulmonary micro-circulation. These features are part of the so-called 'hepatopulmonary syndrome', of which this case appears to represent a less severe form.

Identification of potential target genes for Adr1p through characterization of essential nucleotides in UAS1

Adr1p is a regulatory protein in the yeast Saccharomyces cerevisiae that binds to and activates transcription from two sites in a perfect 22-bp inverted repeat, UAS1, in the ADH2 promoter. Binding requires two C2H2 zinc fingers and a region amino terminal to the fingers. The importance for DNA binding of each position within UAS1 was deduced from two types of assays. Both methods led to an identical consensus sequence containing only four essential base pairs: GG(A/G)G. The preferred sequence, TTGG(A/G)GA, is found in both halves of the inverted repeat. The region of Adr1p amino terminal to the fingers is important for phosphate contacts in the central region of UAS1. However, no base-specific contacts in this portion of UAS1 are important for DNA binding or for ADR1-dependent transcription in vivo. When the central 6 bp were deleted, only a single monomer of Adr1p was able to bind in vitro and activation in vivo was severely reduced. On the basis of these results and previous knowledge about the DNA binding site requirements, including constraints on the spacing and orientation of sites that affect activation in vivo, a consensus binding site for Adr1p was derived. By using this consensus site, potential Adr1p binding sites were located in the promoters of genes known to show ADR1-dependent expression. In addition, this consensus allowed the identification of new potential target genes for Adr1p.

ADH2 expression is repressed by REG1 independently of mutations that alter the phosphorylation of the yeast transcription factor ADR1

In Saccharomyces cerevisiae, expression of the ADH2 gene is undetectable during growth on glucose. The transcription factor ADR1 is required to fully activate expression when glucose becomes depleted. Partial activation during growth on glucose occurred in cells carrying a constitutive allele of ADR1 in which the phosphorylatable serine of a cyclic AMP (cAMP)-dependent protein kinase phosphorylation site had been changed to alanine. When glucose was removed from the growth medium, a substantial increase in the level of this constitutive expression was observed for both the ADH2 gene and a reporter construct containing the ADR1 binding site. This suggests that glucose can block ADR1-mediated activation independently of cAMP-dependent phosphorylation at serine 230. REG1/HEX2/SRN1 was identified as a potential serine 230-independent repressor of ADH2 expression. Yeast strains carrying a deletion of the REG1 gene, reg1-1966, showed a large increase in ADR1-dependent expression of ADH2 during growth on glucose. A smaller increase in ADR1-independent expression was also observed. Additionally, an increase in the level of ADR1 expression and posttranslational modification of the ADR1 protein were observed. When the reg1-1966 allele was combined with various ADR1 constitutive alleles, the level of ADH2 expression was synergistically elevated. This indicates that REG1 can act independently of phosphorylation at serine 230. Our results suggest that glucose repression in the presence of ADR1 constitutive alleles occurs primarily through a REG1-dependent pathway which appears to affect ADH2 transcription at multiple levels.

A mutation outside the two zinc fingers of ADR1 can suppress defects in either finger

A second-site mutation that restored DNA binding to ADR1 mutants altered at different positions in the two zinc fingers was identified. This mutation (called IS1) was a conservative change of arginine 91 to lysine in a region amino terminal to the two zinc fingers and known from previous experiments to be necessary for DNA binding. IS1 increased binding to the UAS1 sequence two- to sevenfold for various ADR1 mutants and twofold for wild-type ADR1. The change of arginine 91 to glycine decreased binding twofold, suggesting that this arginine is involved in DNA binding in the wild-type protein. The increase in binding by IS1 did not involve protein-protein interactions between the two ADR1 monomers, nor did it require the presence of the sequences flanking UAS1. However, the effect of IS1 was influenced by the sequence of the first finger, suggesting that interactions between the region amino terminal to the fingers and the fingers themselves could exist. A model for the role of the amino-terminal region based on these results and sequence homologies with other DNA-binding motifs is proposed.

Identification and characterization of three genes that affect expression of ADH2 in Saccharomyces cerevisiae

Using a new selection protocol we have identified and preliminarily characterized three new loci (ADR7, ADR8 and ADR9) which affect ADH2 (alcohol dehydrogenase isozyme II) expression. Mutants were selected which activate ADH2 expression in the presence of an over-expressed, normally inactive ADR1 allele. The mutants had very similar phenotypes with the exception that one was temperature sensitive for growth. In the absence of any ADR1 allele, the mutants allowed ADH2 to partially escape glucose repression. However, unlike wildtype strains deleted for ADR1, the mutants were able to efficiently derepress ADH2. The mutations allowed a small escape from glucose repression for secreted invertase, but had no effect on the glucose repression of isocitrate lyase or malate dehydrogenase. The mutations were shown to be nonallelic to a wide variety of previously characterized mutations, including mutations that affect other glucose-repressed enzymes.

Mutations in the zinc fingers of ADR1 that change the specificity of DNA binding and transactivation

ADR1 is a yeast transcription factor that contains two zinc fingers of the Cys-2-His-2 (C2H2) class. Mutations that change the specificity of DNA binding of ADR1 to its target site, upstream activation sequence 1 (UAS1), have been identified at three positions in the first zinc finger. Mutations Arg-115 to Gln, His-118 to Thr, and Arg-121 to Asn led to new specificities of DNA binding at adjacent positions 10, 9, and 8 (3'-GAG-5') in UAS1. Arg-115 is at the finger tip, and His-118 and Arg-121 are at positions 3 and 6, respectively, in the alpha helix of finger 1. One double mutant displayed the binding specificity expected from the properties of its constituent new-specificity mutations. Mutations in the second finger that allowed its binding site to be identified through loss-of-contact phenotypes were made. These mutations imply a tail-to-tail orientation of the two ADR1 monomers on their adjacent binding sites. Finger 1 is aligned on UAS1 in an amino-to-carboxyl-terminal orientation along the guanine-rich strand in a 3'-to-5' direction. One of the ADR1 mutants was functional in vivo with both its cognate binding site and wild-type UAS1, but the other two mutants were defective in transactivation despite their ability to bind with high affinity to their cognate binding sites.

Alanine scanning site-directed mutagenesis of the zinc fingers of transcription factor ADR1: residues that contact DNA and that transactivate

To identify functionally important amino acids in the two zinc fingers of transcription factor ADR1 [alcohol dehydrogenase (ADH) II synthesis regulator], oligonucleotide-directed mutagenesis was used to substitute alanine for the original amino acid at each position in both fingers. The effects of these mutations on DNA binding and thermal stability of ADR1 in vitro and on activation of ADH2 expression in vivo were measured. The DNA binding activity was remarkably heatstable. Amino acids that are candidates for DNA contact sites were identified in the finger-tip and alpha-helical region of each finger, three in the first finger and two in the second. Unexpectedly, an acidic residue in the first finger was essential for transactivation, but its replacement by alanine had no effect on DNA binding. Substitution at several highly conserved positions did not affect ADR1 functions. The ADR1 zinc fingers appear to make relatively few energetically significant contacts to DNA, perhaps as few as three in the first finger and one in the second.

cAMP-dependent phosphorylation and inactivation of yeast transcription factor ADR1 does not affect DNA binding

Transcription factor ADR1 increases the level of ADH2 gene expression 200-fold by binding to a palindromic upstream activation sequence (UAS1) in the glucose-repressible ADH2 promoter in Saccharomyces cerevisiae. cAMP-dependent protein kinase (cAPK) phosphorylates ADR1 in vitro and a yeast strain with elevated cAPK activity inhibits the ability of ADR1 to activate ADH2 transcription in vivo [Cherry, J. R., Johnson, T. R., Dollard, C., Schuster, J. R. & Denis, C. L. (1988) Cell 56, 409-419]. Intact ADR1 protein was detected at comparable levels in extracts made from repressed or derepressed yeast cells, indicating that glucose repression is not due to absence of ADR1. ADR1 in extracts made from glucose-repressed and -derepressed cells bound UAS1 DNA with similar affinities despite having greatly different abilities to activate ADH2 gene expression in vivo. A mutant form of ADR1 encoded by ADR1-5c, which has an altered consensus sequence for phosphorylation by cAPK conferred constitutive expression on ADH2 but bound DNA to the same extent as wild-type ADR1 protein. Similarly, normal DNA binding was seen for ADR1 produced in mutants with altered levels of cAPK activity. Because inactivation of ADR1 by phosphorylation has no detectable effect on either DNA binding or ADR1 levels, ADR1 probably binds to UAS1 constitutively and phosphorylation prevents it from promoting transcription.

Mutant alcohol dehydrogenase (ADH III) presequences that affect both in vitro mitochondrial import and in vitro processing by the matrix protease

Point mutations in the presequence of the mitochondrial alcohol dehydrogerase isoenzyme (ADH III) have been shown to affect either the import of the precursor protein into yeast mitochondria in vivo or its processing within the organelle. In the present work, the behavior of these mutants during in vitro import into isolated mitochondria was investigated. All point mutants tested were imported with a slower initial rate than that of the wild-type precursor. This defect was corrected when the precursors were treated with urea prior to import. Once imported, the extent of processing to the mature form of mutant precursors varied greatly and correlated well with the defects observed in vivo. This result was not affected by prior urea treatment. When matrix extracts enriched for the processing protease were used, this defect was shown to be due to failure of the protease to efficiently recognize or cleave the presequence, rather than to a lack of access to the precursor. The rate of import of two ADH III precursors bearing internal deletions in the leader sequence was similar to those of the point mutants, whereas a deletion leading to the removal of the 15 amino-terminal amino acids was poorly imported. The mature amino terminus of wild-type ADH III was determined to be Gln-25. Mutant m01 (Ser-26 to Phe), which reduced the efficiency of cleavage in vitro by 80%, was cleaved at the correct site.

Spectroscopic studies of wild-type and mutant "zinc finger" peptides: determinants of domain folding and structure

The "zinc finger" model [Miller, J., McLachlan, A. D. & Klug, A. (1985) EMBO J. 4, 1609-1614; Brown, R. S., Sander, C. & Argos, P. (1985) FEBS Lett. 186, 271-274] makes both specific structural and specific functional predictions about zinc finger consensus sequences that can be tested with a combination of genetic, molecular biological, and biophysical techniques. The yeast transcription factor ADR1 contains two adjacent zinc finger domains; genetic and deletion analyses showed that amino acid substitutions and deletions in the zinc finger domains resulted in the loss of protein activity. To test the structural and folding predictions of the zinc finger model, peptides encompassing each of the ADR1 fingers were synthesized (ADR1a and ADR1b) as well as a mutant finger peptide (del138) deleted for a single amino acid residue. The folding and metal-binding characteristics of these were assessed by 1H nuclear magnetic resonance (NMR) and visible spectroscopy. While a single unique conformational species was detected for the two wild-type peptides upon tetrahedral binding of zinc, the deletion peptide did not bind zinc with tetrahedral geometry, nor did it fold into a zinc finger domain. The metal-binding and folding results found with the mutant peptide were similar to those obtained when thiol alkylation or imidazole protonation of the wild-type peptides was performed. These data indicate that ligand spacing and both thiol and imidazole participation in zinc binding are specific and necessary requirements for zinc finger folding, which provides direct support for the initial predictions of the model.

Mutations in the signal sequence of prepro-alpha-factor inhibit both translocation into the endoplasmic reticulum and processing by signal peptidase in yeast cells

The effects of five single-amino-acid substitution mutations within the signal sequence of yeast prepro-alpha-factor were tested in yeast cells. After short pulse-labelings, virtually all of the alpha-factor precursor proteins from a wild-type gene were glycosylated and processed by signal peptidase. In contrast, the signal sequence mutations resulted in the accumulation of mostly unglycosylated prepro-alpha-factor after a short labeling interval, indicating a defect in translocation of the protein into the endoplasmic reticulum. Confirming this interpretation, unglycosylated mutant prepro-alpha-factor in cell extracts was sensitive to proteinase K and therefore in a cytosolic location. The signal sequence mutations reduced the rate of translocation into the endoplasmic reticulum by as much as 25-fold or more. In at least one case, mutant prepro-alpha-factor molecules were translocated almost entirely posttranslationally. Four of the five mutations also reduced the rate of proteolytic processing by signal peptidase in vivo, even though the signal peptide alterations are not located near the cleavage site. This study demonstrates that a single-amino-acid substitution mutation within a eucaryotic signal peptide can affect both translocation and proteolytic processing in vivo and may indicate that the recognition sequences for translocation and processing overlap within the signal peptide.

Serial studies on the affinity and heterogeneity of human autoantibodies to thyroglobulin

The functional affinity and heterogeneity of autoantibodies to thyroglobulin (Tg) were measured by an IgG subclass-specific solid-phase competition ELISA in patients with autoimmune thyroid disease. High-affinity IgG1 and IgG4 antibodies formed the major anti-Tg response. Both titre and affinity of IgG3 and IgG2 anti-Tg were generally low but in some Hashimoto's disease patients high-affinity IgG2 anti-Tg were found and IgG2 anti-Tg, unlike those of other subclasses, showed very restricted heterogeneity. The affinity of IgG4 anti-Tg was similar in patients with thyroid disease and their clinically euthyroid (normal) relatives. In contrast, a progressive increase in IgG1 anti-Tg affinity was seen in clinically euthyroid individuals compared with their relatives with thyroid disease and high titred Hashimoto's disease patients, suggesting that either rising titres of high affinity IgG1 anti-Tg or affinity maturation of IgG1 anti-Tg may be indicative of impending hypothyroidism.

Localization of a minimal binding domain and activation regions in yeast regulatory protein ADR1

ADR1 is a transcription factor required for activation of the glucose-repressible alcohol dehydrogenase 2 (ADH2) gene in Saccharomyces cerevisiae. ADR1 has two zinc finger domains between amino acids 102 and 159, and it binds to an upstream activation sequence (UAS1) in the ADH2 promoter. A functional dissection of ADR1 was performed by using a series of amino- and carboxy-terminal deletion mutants of ADR1, most of which were fused to the Escherichia coli beta-galactosidase. These deletion mutants were assayed for binding to UAS1 in vitro, for the ability to activate ADH2 transcription in vivo, and for level of expression. Deletion of ADR1 amino acids 150 to 172 and 76 to 98 eliminated DNA binding in vitro, which accounted for the loss of transcriptional activation in vivo. Results with the former deletion mutant indicated that both of the ADR1 zinc fingers are necessary for sequence-specific DNA binding. Results with the latter deletion mutant suggested that at least part of the sequence between amino acids 76 to 98, in addition to the two finger domains, is required for high-affinity DNA binding. The smallest fusion protein able to activate ADH2 transcription, containing ADR1 amino acids 76 to 172, was much less active in vivo than was the longest fusion protein containing amino acids 1 to 642 of ADR1. In addition, multiple regions of the ADR1 polypeptide (including amino acids 40 to 76, 260 to 302, and 302 to 505), which are required for full activation of ADH2, were identified. An ADR1-beta-galactosidase fusion protein containing only the amino-terminal 16 amino acids of ADR1 was present at a much higher level than were larger fusion proteins, which suggested that the sequences within ADR1 influence the expression of the gene fusion.

Adjacent upstream activation sequence elements synergistically regulate transcription of ADH2 in Saccharomyces cerevisiae

A 22-base-pair (bp) inverted repeat present in the ADH2 promoter is an upstream activation sequence (UAS1) which confers ADR1-dependent activation upon a heterologous Saccharomyces cerevisiae promoter. UAS1 was nonfunctional when placed within an intron 3' to the transcription start site. The 11-bp sequence which constitutes one-half of the UAS1 palindrome did not activate transcription in a single copy, as direct repeats, or in an inverted orientation opposite to that of ADH2 UAS1. Furthermore, two pairs of symmetrical point mutations within UAS1 significantly reduced activation. This result suggests that a specific orientation of sequences within UAS1 is necessary for ADR1-dependent activation. We determined that an ADR1-dependent complex was formed with UAS1 and, to a lesser extent, with the nonfunctional 11-bp half palindrome. However, the 11 bp did not confer UAS activity, suggesting that ADR1 binding is not sufficient for activation in vivo. ADR1 did not bind to mutant UAS1 sequences in vitro, indicating that their decreased activation is attributable to a reduced affinity of ADR1 for these sequences. We also identified an additional 20-bp ADH2 element (UAS2) that increased the expression of CYC1-lacZ 20-fold when combined with UAS1. UAS2 permitted ADR1-independent, glucose-regulated expression of the hybrid gene. Consistent with this observation, ADR1 did not form a detectable complex with UAS2. Deletion of UAS2 at the chromosomal ADH2 locus virtually abolished ADH2 derepression and had no effect on glucose repression.

The yeast ADR6 gene encodes homopolymeric amino acid sequences and a potential metal-binding domain

The ADR6 gene of Saccharomyces cerevisiae has an open reading frame which could encode a polypeptide of 1314 amino acids. The predicted mRNA encodes a protein with homopolymeric stretches of asparagine and threonine, particularly near its amino terminus and contains additional sequences consisting of polyglutamine repeats. The predicted protein also contains a potential metal binding (Cys)4-type finger near its carboxy-terminus. An ADR6/beta-galactosidase fusion protein was predominantly nuclear in location, consistent with its role as an activator of ADH2 transcription.

The yeast regulatory protein ADR1 binds in a zinc-dependent manner to the upstream activating sequence of ADH2

The yeast ADR1 protein contains two zinc finger domains that are essential for its role in transcriptional activation of alcohol dehydrogenase (ADH2). These domains are thought to function as DNA-binding structures. An ADR1-beta-galactosidase fusion protein made in Escherichia coli and containing the finger domains of ADR1 binds in vitro in a zinc-dependent manner to DNA fragments containing the two ADH2 upstream activation sequences. The strongest binding is to upstream activation sequence 1, a 22-base-pair palindrome.

Zinc-dependent structure of a single-finger domain of yeast ADR1

In the proposed "zinc finger" DNA-binding motif, each repeat unit binds a zinc metal ion through invariant Cys and His residues and this drives the folding of each 30-residue unit into an independent nucleic acid-binding domain. To obtain structural information, we synthesized single and double zinc finger peptides from the yeast transcription activator ADR1, and assessed the metal-binding and DNA-binding properties of these peptides, as well as the solution structure of the metal-stabilized domains, with the use of a variety of spectroscopic techniques. A single zinc finger can exist as an independent structure sufficient for zinc-dependent DNA binding. An experimentally determined model of the single finger is proposed that is consistent with circular dichroism, one- and two-dimensional nuclear magnetic resonance, and visual spectroscopy of the single-finger peptide reconstituted in the presence of zinc.

Single-amino-acid substitutions within the signal sequence of yeast prepro-alpha-factor affect membrane translocation

We used a genetic approach to identify point mutations in the signal sequence of a secreted eucaryotic protein, yeast alpha-factor. Signal sequence mutants were obtained by selecting for cells that partially mistargeted into mitochondria a fusion protein consisting of the alpha-factor signal sequence fused to the mature portion of an imported mitochondrial protein (Cox IV). The mutations resulted in replacement of a residue in the hydrophobic core of the signal sequence with either a hydrophilic amino acid or a proline. After reassembly into an intact alpha-factor gene, the substitutions were found to decrease up to 50-fold the rate of translocation of prepro-alpha-factor across microsomal membranes in vitro. Two of three mutants tested produced lower steady-state levels of alpha-factor in intact yeast cells, although the magnitude of the effect was less than that in the cell-free system.

Regulation of expression and activity of the yeast transcription factor ADR1

Disruption of ADR1, a positive regulatory gene in the yeast Saccharomyces cerevisiae, abolished derepression of ADH2 but did not affect glucose repression of ADH2 or cell viability. The ADR1 mRNA was 5 kilobases long and had an unusually long leader containing 509 nucleotides. ADR1 mRNA levels were regulated by the carbon source in a strain-dependent fashion. beta-Galactosidase levels measured in strains carrying an ADR1-lacZ gene fusion paralleled ADR1 and ADR1-lacZ mRNA levels, indicating a lack of translational regulation of ADR1 mRNA. ADH2 was regulated by the carbon source to the same extent in all strains examined and showed complete dependence on ADR1 as well. The expression of ADR1 mRNA and an ADR1-beta-galactosidase fusion protein during glucose repression suggested that the activity of the ADR1 protein is regulated at the posttranslational level to properly regulate ADH2 expression. The ADR1-beta-galactosidase fusion protein was able to activate ADH2 expression during glucose repression but showed significantly higher levels of activation upon derepression. A similar result was obtained when ADR1 was present on a multicopy plasmid. These results suggest that low-level expression of ADR1 is required to maintain glucose repression of ADH2 and are consistent with the hypothesis that ADR1 is regulated at the posttranslational level.

Prediction of remission after antithyroid drug treatment in Graves' disease

A prospective study was carried out to determine the factors which influence response to antithyroid drug treatment in Graves' disease and to assess their predictive value. Eleven variables were included in the assessment and were subjected to discriminant analysis, log rank test and "survival" analysis. The patients were observed for a considerable period (mean duration 51 months). Carbimazole (mean total dose 8 g) was given in combination with thyroxine for an average of eight months to 72 patients. Thirty-five patients relapsed and 37 remain in remission. Thyrotrophin binding inhibiting immunoglobulins (TBII) were detectable in 74 per cent of patients at diagnosis and thyroid stimulating antibodies detectable in 70 per cent. At the end of treatment thyrotrophin binding inhibiting immunoglobulins and thyroid stimulating antibodies were present in 36 and 27 per cent of patients respectively. Levels of thyrotrophin binding inhibiting immunoglobulins were significantly higher both before and after treatment in the group who relapsed, but were not of prognostic significance in an individual patient unless the value was extremely high (TBII index greater than 70). The presence of thyroid stimulating antibodies was of no value in predicting outcome. HLA typing confirmed the known association of Graves' disease with HLA B8 and HLA DR3 but neither of these antigens conferred and increased likelihood of relapse. The likelihood of relapse is shown to be directly related to the severity of the disease at the time of diagnosis, as measured by the serum total T3, and to the size of the thyroid gland; it is not affected by age, family history of thyroid disease or ophthalmopathy. The data indicate that antithyroid drug treatment can be expected to induce long-term remission in patients with mild disease (T3 less than 5 nmol/l) and small thyroids; carbimazole at this dose level is inappropriate for patients with severe disease (T3 greater than 9 nmol/) and large goitres.

Ionized hypocalcemia after fresh frozen plasma administration to thermally injured children: effects of infusion rate, duration, and treatment with calcium chloride

A number of cardiac arrests and severe hypotensive episodes have been witnessed associated with the intravenous infusion of fresh frozen plasma (FFP). To clarify the possible role of hypocalcemia, 28 thermally injured anesthetized pediatric patients with massive blood loss were studied to examine the cardiovascular responses (mean arterial pressure [MAP], heart rate, ECG) to 49 infusions of FFP. Rapid, statistically significant reductions in ionized calcium ([Ca2+]) followed each of four rates (1.0, 1.5, 2.0, and 2.5 ml.kg-1.min-1 for 5 minutes) of FFP infusion (P less than 0.0001). The slowest rate resulted in significantly less reduction in [Ca2+] than did the higher infusion rates (P less than 0.002). In five children MAP decreased greater than or equal to 20% below baseline levels, but this was not correlated with rate of FFP administration or decrease in [Ca2+]. The decreases in [Ca2+] and MAP were inversely related to age and unrelated to anesthetic technique. Changes in the Q-oTc interval were not related to [Ca2+]. Adverse cardiovascular responses and reduced [Ca2+] were not significantly different between 5- and 10-minute FFP infusions. Fewer fluctuations in MAP occurred when calcium chloride (CaCl2) was administered; the least fluctuation in [Ca2+] occurred when CaCl2 was administered during the plasma infusion. It is concluded that in thermally injured children 1-17 years old: 1) Rapid infusions of FFP produce sudden but evanescent decreases in [Ca2+]; more rapid infusions result in greater reductions in [Ca2+]. 2) There is no correlation between [Ca2+] and systemic hypotension. 3) Clinically important decreases in MAP occasionally accompany the rapid infusion of FFP.(ABSTRACT TRUNCATED AT 250 WORDS)

The identification and characterization of ADR6, a gene required for sporulation and for expression of the alcohol dehydrogenase II isozyme from Saccharomyces cerevisiae

The alcohol dehydrogenase II isozyme (enzyme, ADHII; structural gene, ADH2) of the yeast, Saccharomyces cerevisiae, is under stringent carbon catabolite control. This cytoplasmic isozyme exhibits negligible activity during growth in media containing fermentable carbon sources such as glucose and is maximal during growth on nonfermentable carbon sources. A recessive mutation, adr6-1, and possibly two other alleles at this locus, were selected for their ability to decrease Ty-activated ADH2-6c expression. The adr6-1 mutation led to decreased ADHII activity in both ADH2-6c and ADH2+ strains, and to decreased levels of ADH2 mRNA. Ty transcription and the expression of two other carbon catabolite regulated enzymes, isocitrate lyase and malate dehydrogenase, were unaffected by the adr6-1 mutation. adr6-1/adr6-1 strains were defective for sporulation, indicating that adr6 mutations may have pleiotropic effects. The sporulation defect was not a consequence of decreased ADH activity. Since the ADH2-6c mutation is due to insertion of a 5.6-kb Ty element at the TATAA box, it appears that the ADR6+-dependent ADHII activity required ADH2 sequences 3' to or including the TATAA box. The ADH2 upstream activating sequence (UAS) was probably not required. The ADR6 locus was unlinked to the ADR1 gene which encodes another trans-acting element required for ADH2 expression.

The cloning and mapping of ADR6, a gene required for sporulation and for expression of the alcohol dehydrogenase II isozyme from Saccharomyces cerevisiae

The alcohol dehydrogenase II (ADH2) gene of the yeast, Saccharomyces cerevisiae, is not transcribed during growth on fermentable carbon sources such as glucose. Growth of yeast cells in a medium containing only nonfermentable carbon sources leads to a marked increase or derepression of ADH2 expression. The recessive mutation, adr6-1, leads to an inability to fully derepress ADH2 expression and to an inability to sporulate. The ADR6 gene product appears to act directly or indirectly on ADH2 sequences 3' to or including the presumptive TATAA box. The upstream activating sequence (UAS) located 5' to the TATAA box is not required for the Adr6- phenotype. Here, we describe the isolation of a recombinant plasmid containing the wild-type ADR6 gene. ADR6 codes for a 4.4-kb RNA which is present during growth both on glucose and on nonfermentable carbon sources. Disruption of the ADR6 transcription unit led to viable cells with decreased ADHII activity and an inability to sporulate. This indicates that both phenotypes result from mutations within a single gene and that the adr6-1 allele was representative of mutations at this locus. The ADR6 gene mapped to the left arm of chromosome XVI at a site 18 centimorgans from the centromere.

Two zinc fingers of a yeast regulatory protein shown by genetic evidence to be essential for its function

The best-understood protein structure involved in DNA binding is the helix-turn-helix motif. A second DNA-binding domain, the finger structure, has been proposed on the basis of sequence analysis, partial proteolysis and zinc content of Xenopus transcription factor TFIIIA. Other eukaryotic proteins were subsequently found to contain contiguous repeat units of the postulated finger motif. Each repeat unit contains thirty amino acids and is thought to bind a zinc atom using two cysteines and two histidines as ligands. The protein loop or finger between apparent zinc ligands is rich in DNA-binding residues and is thought to make specific contacts with DNA. The yeast protein ADR1, a positive regulator of transcription of the gene ADH2, contains two finger domains in a region of the protein required for transcriptional activation. Nineteen independently isolated adr1 mutations induced by hydroxylamine were found at nine different amino-acid positions, seven of which are in the two finger domains. All four mutations that altered invariant cysteine or histidine residues led to an adr1 null phenotype. Only one other mutation caused an adr1 null phenotype. Thus, one finger domain is not sufficient for ADR1 activity. This provides the first evidence that, as is consistent with the proposed model, the invariant cysteine and histidine residues are essential for the formation of the finger structure.

The efficacy of ranitidine in children

The effect of preoperative oral ranitidine on intragastric pH and volume of aspirate was evaluated in anaesthetized children. Five groups of eight randomly assigned children were evaluated. The first group acted as control and the other groups received 2, 2.5, 3, 3.5 mg kg-1 ranitidine, respectively. The drug was administered 1-4 h preoperatively. The intragastric pH was measured by a pH electrode through an orogastric tube, and the volume of aspirate was recorded every hour. At the time of first measurement oral ranitidine was significantly effective (P less than 0.001) in increasing the pH of intragastric contents to above the safe level of 2.5 in 94% of the children. At the second measurement an hour later, it was effective in all the children. Ranitidine has no significant effect on the volume of gastric aspirate and also there was no significant difference in the effect on the pH of the various doses of ranitidine studied. Oral ranitidine at doses of 2-3.5 mg kg-1 is effective in decreasing gastric acidity in children.

IgG subclass distribution of thyroid autoantibodies: a 'fingerprint' of an individual's response to thyroglobulin and thyroid microsomal antigen

The IgG subclass distribution of autoantibodies to thyroglobulin and thyroid microsomal antigen was studied in 21 patients with Graves' disease during fluctuations in total IgG class autoantibody levels induced by various forms of therapy. In addition, changes in autoantibody subclass distributions were investigated during the natural course of Hashimoto's disease in seven patients taking thyroxine. The autoantibodies were principally of subclasses IgG1 and/or IgG4 in Graves' patients although IgG2 contributed significantly to thyroglobulin antibodies in 5/7 Hashimoto sera. In Graves' disease the distribution of microsomal and thyroglobulin antibodies among the IgG subclasses remained essentially unchanged over periods of 6 months-2 years whether autoantibody levels decreased during carbimazole therapy or increased transiently following 131Iodine treatment or subtotal thyroidectomy. Similar observations were made for thyroglobulin antibodies in Hashimoto patients studied over 2 1/2-4 years; furthermore, the IgG subclass distribution of microsomal antibodies was usually different from that of thyroglobulin antibodies in the same patient. These observations suggest that the microsomal and/or thyroglobulin antibody subclass distribution is characteristic for a particular individual and may be regarded as the 'fingerprint' of an individual's response to these thyroid autoantigens.

Transcription of the ADH2 gene in Saccharomyces cerevisiae is limited by positive factors that bind competitively to its intact promoter region on multicopy plasmids

Transcription of the ADH2 gene in the yeast Saccharomyces cerevisiae was inhibited by excess copies of its own promoter region. This competition effect was promoter specific and required the upstream activation sequence of ADH2 as well as sequences 3' to the TATA box. Introducing excess copies of ADR1, an ADH2-specific regulatory gene, did not alleviate the competition that was observed in these circumstances during both constitutive and derepressed ADH2 expression. Excess copies of the upstream region did not release ADH2 from glucose repression, consistent with the view that ADH2 is regulated by positive trans-acting factors.

Primary structure requirements for correct sorting of the yeast mitochondrial protein ADH III to the yeast mitochondrial matrix space

Alcohol dehydrogenase isoenzyme III (ADH III) in Saccharomyces cerevisiae, the product of the ADH3 gene, is located in the mitochondrial matrix. The ADH III protein was synthesized as a larger precursor in vitro when the gene was transcribed with the SP6 promoter and translated with a reticulocyte lysate. A precursor of the same size was detected when radioactively pulse-labeled proteins were immunoprecipitated with anti-ADH antibody. This precursor was rapidly processed to the mature form in vivo with a half-time of less than 3 min. The processing was blocked if the mitochondria were uncoupled with carbonyl cyanide m-chlorophenylhydrazone. Mutant enzymes in which only the amino-terminal 14 or 16 amino acids of the presequence were retained were correctly targeted and imported into the matrix. A mutant enzyme that was missing the amino-terminal 17 amino acids of the presequence produced an active enzyme, but the majority of the enzyme activity remained in the cytoplasmic compartment on cellular fractionation. Random amino acid changes were produced in the wild-type presequence by bisulfite mutagenesis of the ADH3 gene. The resulting ADH III protein was targeted to the mitochondria and imported into the matrix in all of the mutants tested, as judged by enzyme activity. Mutants containing amino acid changes in the carboxyl-proximal half of the ADH3 presequence were imported and processed to the mature form at a slower rate than the wild type, as judged by pulse-chase studies in vivo. The unprocessed precursor appeared to be unstable in vivo. It was concluded that only a small portion of the presequence contains the necessary information for correct targeting and import. Furthermore, the information for correct proteolytic processing of the presequence appears to be distinct from the targeting information and may involve secondary structure information in the presequence.

The effect of subtotal thyroidectomy with propranolol preparation on antibody activity in Graves' disease

The effect of subtotal thyroidectomy on thyroid stimulating antibodies (TSAb), thyrotrophin binding inhibitory immunoglobulins (TBII) and antimicrosomal antibodies (MsAb) was studied in 26 patients with Graves' hyperthyroidism treated pre-operatively with propranolol, but without antithyroid drugs. Following surgery, two patients relapsed in the first year and eight patients became hypothyroid. Eighteen patients (69%) had detectable TSAb at entry and no significant change in titre was seen during propranolol therapy. Following surgery TSAb levels fell within 24 h in eight patients, and at 6 weeks only seven patients had detectable TSAb. TSAb were still detectable in seven patients at 6 months. TSAb activity did not predict the late relapses. TBII were present in 13 patients (50%) before surgery and titres remained unchanged in all but two patients during the immediate postoperative period. At 6 weeks TBII had disappeared from the serum of only three patients. During the early post-operative period TBII became transiently detectable in five of the 13 patients initially TBII negative. The two patients who subsequently relapsed remained TBII positive throughout. Microsomal antibodies were present in the sera of 22 patients (85%). Surgery was followed by a decline in titre, which was substantial in only six of 13 patients studied in detail. Thus, in 92% patients hyperthyroidism was successfully eradicated. Propranolol treatment had no effect on antibody activity. TSAb and TBII disappeared from the circulation in 61% and 46% patients, respectively. These data are compatible with the concept that lymphocytes within the thyroid are the major site of TSAb production but other important sites for synthesis of thyroidal autoantibodies probably exist. Although outcome from surgery could not be accurately predicted from TSAb or TBII status either pre- or post-operatively, the two patients who relapsed had the most severe disturbances of thyroid autoimmunity; all patients in whom initially detectable TSAb or TBII disappeared remained in remission.