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G S May

Publications and source records attributed to G S May.

At least 55 records · Page 3Linked to original sources
PubMed1990

Sequence, organization and expression of the core histone genes of Aspergillus nidulans.

The core histone gene family of Aspergillus nidulans was characterized. The H2A, H2B and H3 genes are unique in the A. nidulans genome. In contrast there are two H4 genes, H4.1 and H4.2. As previously reported for the H2A gene (May and Morris 1987) introns also interrupt the other core histone genes. The H2B gene, like the H2A gene, is interrupted by three introns, the H3 and H4.1 gene are each interrupted by two introns and the H4.2 gene contains one intron. The position of the single intron in H4.2 is the same as that the first intron of the H4.1 gene. The H2A and H2B genes are arranged as a gene pair separated by approximately 600 bp and are divergently transcribed. The H3 and H4.1 genes are similarly arranged and are separated by approximately 800 bp. The H4.2 gene is not closely linked to either the H2A-H2B or H3-H4.1 gene pairs. Using pulse field gel electrophoresis an electrophoretic karyotype was established for A. nidulans. This karyotype was used to assign the H3-H4.1 gene pair and the H4.2 gene to linkage group VIII and the H2A-H2B gene pair to either linkage group III or VI. The abundance of each of the histone messenger RNAs was determined to be cell cycle regulated but the abundance of the H4.2 mRNA appears to be regulated differently from the others.

Amino Acid Sequence↗
PubMed1989

Characterization of an inducible expression system in Aspergillus nidulans using alcA and tubulin-coding genes.

Plasmids have been constructed in which expression of a gene can be placed under the control of the inducible promoter of the alcA gene encoding alcohol dehydrogenase I in Aspergillus nidulans. Simplified shuttle vectors carrying pyr4 which complements pyrG89 mutations have also been constructed. These are based on pUC19 and retain alpha-peptide expression. The beta-tubulin genes, tubC and benA, have been placed under the control of alcA and their expression studied. Levels of expression can be assayed phenotypically because increased synthesis of beta-tubulin inhibits vegetative growth. Sensitivity of asexual spore formation to the anti-microtubule drug benomyl provides a means of detecting very low levels of expression of the chimeric genes. Glucose almost completely represses the chimeric genes. Induction is rapid and is maximal within an hour. When a strain carrying seven copies of an alcA::tubC gene fusion was grown under inducing conditions, 6.5% of total sulfate labelled protein consisted of tubC product. Cyclopentanone was the most potent inducer of the chimeric genes on solid media but it also partially inhibited growth. Chimeric alcA::tubC and alcA::benA genes were expressed to very similar levels despite the fact that tubC utilizes many rare codons.

Alcohol Dehydrogenase↗
PubMed1989

The highly divergent beta-tubulins of Aspergillus nidulans are functionally interchangeable.

An internal 1.4-kb Bst EII fragment was used to disrupt the benA gene and establish heterokaryons. The heterokaryons demonstrated that the molecular disruption of benA results in a recessive benA null mutation. Conidia from a heterokaryon swell and germinate but cannot undergo nuclear division and are thus inviable. A chimeric beta-tubulin gene was constructed with the benA promoter driving the tubC structural gene. This chimeric gene construction was placed on a plasmid containing a selectable marker for Aspergillus transformation and the gene disrupting fragment of benA. Integration of this plasmid at benA by the internal gene disrupting fragment of benA simultaneously disrupts the benA gene and replaces it with the chimeric beta-tubulin gene, rescuing the benA null generated by the integration. Strains generated by this procedure contain only tubC beta-tubulin for all beta-tubulin functions. Strains having only tubC beta-tubulin are viable and exhibit no detectable microtubule dysfunction though they are more sensitive than wild-type strains to the antimicrotubule drug benomyl. It is concluded that the two beta-tubulin genes of Aspergillus nidulans, though highly divergent, are interchangeable.

Aspergillus nidulans↗
PubMed1988

Developmental regulation of a conidiation specific beta-tubulin in Aspergillus nidulans.

A beta-tubulin gene previously suggested to participate in conidial development in the filamentous fungus Aspergillus nidulans is shown to be developmentally regulated in its expression. A quantitative S1 assay was used to show that the abundance of the tubC messenger RNA increases during conidial development relative to the benA messenger RNA. Morphological analysis of cultures, used to prepare RNA for the S1 analysis, demonstrated that the increase in tubC messenger RNA was directly correlated with the appearance of conidiating cell types and structures and that as these cell types become more prevalent in the culture, the level of the messenger RNA increases. Two-dimensional gel electrophoresis of labeled proteins showed that the relative increase in tubC messenger RNA was reflected in an increase in the tubC protein beta 3. RNA blot hybridization analysis and in vitro translation of total RNA from mycelia and conidia were used to demonstrate that both benA and tubC beta-tubulin messenger RNAs are absent from conidia.

Aspergillus nidulans↗
PubMed1987

The unique histone H2A gene of Aspergillus nidulans contains three introns.

The histone H2A gene of the filamentous fungus Aspergillus nidulans has been cloned and sequenced. There is a single H2A gene in the genome of A. nidulans, and it contains three introns. The introns are 51 nucleotides (nt), 56 nt and 50 nt in length and split codons for amino acids (aa) 18, 48 and 116 of the predicted protein. The transcriptional start and termination points have been determined using an S1 nuclease protection assay. The predicted protein is 132 aa residues in length and surprisingly has a threonine after the initiator methionine instead of the usual serine. The sequence of the predicted histone H2A protein is compared to histone H2A proteins from Schizosaccharomyces pombe, Saccharomyces cerevisiae and calf thymus. Comparison of the amino acid sequence to these other H2A proteins shows that the divergence of amino acid sequences between H2A proteins is found in two clustered sites.

Amino Acid Sequence↗
PubMed1987

Cloning, mapping and molecular analysis of the pyrG (orotidine-5'-phosphate decarboxylase) gene of Aspergillus nidulans.

We have modified the transformation procedures of Ballance et al. [Biochem. Biophys. Res. Commun. 112 (1983) 284-289] to give increased rates of transformation in Aspergillus nidulans. With the modified procedures we have been able to complement pyrG89, a mutation in the orotidine-5'-phosphate decarboxylase gene of A. nidulans, by transformation with a library of wild-type (wt) sequences in pBR329. We have recovered, by marker rescue from one such transformant, a plasmid (pJR15) that carries an A. nidulans sequence that complements pyrG89 efficiently. In three experiments, this plasmid gave an average of 1985 stable transformants/micrograms of transforming DNA. We have analyzed ten of these genetically and by Southern hybridization. In five transformants a single copy of the transforming plasmid had integrated at the pyrG locus, in one transformant several copies of pJR15 had integrated at this locus, in one transformant several copies of the plasmid had integrated into other sites, and in three transformants, the wt allele had apparently replaced the mutant allele with no integration of pBR329 sequences. Sequence and S1 nuclease protection analysis revealed that pJR15 contains a gene that predicts an amino acid sequence with regions of strong homology to the orotidine-5'-phosphate decarboxylases of Neurospora crassa and Saccharomyces cerevisiae. We conclude that this gene is the wt pyrG allele. Finally, we have compared the 5'- and 3'-noncoding sequences and intron splice sequences to other genes of A. nidulans and have mapped the pyrG locus to a region between the fpaB and galD loci on linkage group I.

Aspergillus nidulans↗
PubMed1987

Aspergillus nidulans beta-tubulin genes are unusually divergent.

Aspergillus nidulans has two beta-tubulin genes: benA, which is involved in both vegetative growth and asexual sporulation, and tubC, which is involved mainly in asexual sporulation. Both genes have now been cloned and sequenced. benA encodes a polypeptide of 447 amino acids (aa) and tubC encodes one of 449 aa. The two polypeptides differ by 78 aa residues but the net charge for the two proteins remains the same. The divergence between the amino acid sequences of the Aspergillus beta-tubulins is greater than that for any other two beta-tubulins yet described in the same organism. The benA gene has eight introns and the tubC gene has five, all of which correspond in amino acid position to introns in benA. The positions of some of these introns are conserved in other beta-tubulin genes. The 5'-splice site, internal, and 3'-splice site consensus sequences are similar to those found in other fungal introns. The transcriptional start points for each gene have been determined using primer extension and/or S1 nuclease mapping. Neither the benA gene nor the tubC gene contains a TATA sequence in its 5'-flanking region. The tubC gene has two repeated upstream sequences which are not found in benA. The sites of polyadenylation have been determined for each gene using S1 nuclease mapping. Neither gene contains a polyadenylation signal, AATAAA, typical of other eukaryotic genes.

Amino Acid Sequence↗
PubMed1987

Regulation of the mRNA levels of nimA, a gene required for the G2-M transition in Aspergillus nidulans.

The temperature-sensitive cell cycle mutation nimA5 causes nuclei of Aspergillus nidulans to be blocked in late G2 at restrictive temperature. Under these conditions the spindle pole body divides but does not separate and the mitotic index drops to zero. If nimA5 is blocked for more than one doubling time and then shifted from restrictive to permissive temperature, nuclei immediately enter mitosis, the mitotic spindle forms, and the chromosomes condense (Oakley, B. R., and N. R. Morris, 1983, J. Cell Biol., 96:1155-8). We have cloned the wild-type nimA gene by DNA-mediated complementation of the nimA5 mutant phenotype and have characterized nimA mRNA expression by Northern blot analysis. The transcript is 3.6 kb in length and is under tight nuclear cycle regulation. In synchronously dividing cells, the levels of nimA mRNA become elevated as cells enter mitosis and drop sharply as cells progress through mitosis. Cells blocked in S-phase with hydroxyurea have very low levels of nimA mRNA. Cells blocked in mitosis, either by the antimitotic agent benomyl or by the cell cycle mutation bimE7, maintain elevated levels of the nimA transcript. These data demonstrate not only that nimA is required for entry into mitosis, but because the transcript is normally expressed cyclically and is under tight cell cycle control, they suggest that nimA may play a regulatory role in the initiation of mitosis.

Aspergillus nidulans↗
PubMed1985

Pentoxifylline treatment of moderate to severe chronic occlusive arterial disease.

A pilot study of the effects of pentoxifylline in 19 patients with moderate to severe chronic occlusive arterial disease (COAD) is described. The severity of disease was assessed by the degree of limitation in the walking distance on the flat surface (less than 100 m), the absence of peripheral pulses on palpation, the diminished Doppler tibial/brachial pressure (the ischemic index) at rest, and by contrast arteriography, when available. After a 2-week washout phase, all subjects received pentoxifylline (1200 mg/day) in an open-label manner for a total of 12 weeks. Twelve of the nineteen patients showed a definite increase in exercise tolerance by the end of the study, with a concomitant reduction in ischemic symptoms. All except 3 patients felt they had derived benefit from the medication. In contrast to the clear improvements in walking distance and symptoms, only small effects on noninvasive vascular laboratory measurements were noted. Platelet aggregation, induced by ADP, epinephrine, and collagen, gradually decreased over the study period. Pentoxifylline appears to be useful in the medical management of patients with moderate to severe chronic occlusive arterial disease; future controlled trials in such patients are now justified.

Aged↗
PubMed1985

Involvement of a particular species of beta-tubulin (beta 3) in conidial development in Aspergillus nidulans.

Strains of Aspergillus containing the benA22 mutation are resistant to benomyl for vegetative growth but do not produce conidia. To test whether conidiation involved an additional benomyl-sensitive tubulin (i.e., was mediated by a tubulin other than the tubulins coded for by the benA locus), a collection of mutants was produced that formed conidia in the presence of benomyl, i.e., were conidiation-resistant (CR-) mutants. We analyzed the tubulins of these CR- mutants using two-dimensional gel electrophoresis and found that the mutants lacked one species of beta-tubulin (designated beta 3). We have examined two of these mutants in detail. In crosses with strains containing wild-type tubulins, we found that the absence of the beta 3-tubulin co-segregated perfectly with the CR- phenotype. In diploids containing both the benA22 and CR- mutations, we found that the CR- phenotype was recessive and that beta 3-tubulin was present on two-dimensional gels of tubulins prepared from these diploids. In another set of crosses, these two CR- strains and seven others were first made auxotrophic for uridine and then crossed against strains that had homologously integrated a plasmid containing an incomplete internal fragment of the beta 3-tubulin gene and the pyr4 gene of Neurospora crassa (which confers uridine prototrophy on transformants). If the CR- phenotype were produced by a mutation in a gene distinct from the structural gene for beta 3-tubulin (designated the tubC gene), then crossing over should have produced some CR+ segregants among the uridine auxotrophic progeny of the second cross. All of the uridine auxotrophs from this type of cross, however, showed the CR- phenotype, suggesting that the mutation in these strains is at or closely linked to the tubC locus. The most obvious explanation of these results is that beta 3-tubulin is ordinarily used during conidiation and the presence of this species of beta-tubulin renders conidiation sensitive to benomyl. In the CR- mutants, beta 3-tubulin is absent, and in the presence of the benA22 mutation the benomyl-resistant beta 1-and/or beta 2-tubulin substitutes for beta 3 to make conidiation benomyl resistant. We discuss these results and give two models to explain the interactions between these beta-tubulin species.

Aspergillus nidulans↗
PubMed1985

Identification and functional analysis of beta-tubulin genes by site specific integrative transformation in Aspergillus nidulans.

We have cloned two different beta-tubulin sequences from the filamentous fungus Aspergillus nidulans. Each was used in the construction of transforming plasmids that carry the pyr4 gene of Neurospora crassa. We used these plasmids to transform a pyrG-strain of Aspergillus to uridine prototrophy. Both plasmids were shown to integrate site specifically into the homologous chromosomal sequences. We then used transformant strains in genetic crosses to demonstrate that one of the cloned beta-tubulin sequences was the benA beta-tubulin gene, which codes for the beta 1-and beta 2-tubulins. The other cloned beta-tubulin sequence was shown to be the structural gene for beta 3-tubulin by gene disruption and to participate in conidial development. This is the first report of a gene disruption by site specific, integrative recombination in Aspergillus nidulans.

Aspergillus nidulans↗
PubMed1984

Effect of long-term prophylactic treatment on survival after myocardial infarction.

Survivors of the acute phase of a myocardial infarction still have an increased risk of dying, primarily due to causes directly attributable to their coronary heart disease. This review of randomized clinical trials of various interventions with the potential to prolong life in these patients is an attempt to answer a vitally important question. What, if anything, can be done to improve the long-term prognosis in patients who have survived the initial one or two weeks after suffering an acute myocardial infarction? Seven classes of intervention are considered: anticoagulants, platelet-active drugs, lipid-lowering regimens, antiarrhythmic agents, physical exercise, calcium antagonists and beta-blockers. So far only beta-blockers have been shown to have a favorable effect on long-term survival. Many of the trials reviewed had design limitations; in particular, the sample size was often too small for the results to be conclusive.

Adrenergic beta-Antagonists↗
PubMed1982

Functional modification of the Chlamydomonas flagellar surface.

Chlamydomonas flagella exhibit force transduction in association with their surface. This flagellar surface motility is probably used both for whole cell gliding movements (flagella-substrate interaction) and for reorientation of flagella during mating (flagella-flagella interaction). The present study seeks to identify flagellar proteins that may function as exposed adhesive sites coupled to a motor responsible for their translocation in the plane of the plasma membrane. The principal components of the flagellar membrane are a pair of glycoproteins (approximately 350,000 mol wt), with similar mobility on SDS polyacrylamide gels. A rabbit IgG preparation has been obtained which is specific for these two glycoproteins; this antibody preparation binds to and agglutinates cells by their flagellar surfaces only. Treatment of cells with 0.1 mg/ml pronase results in a loss of motility-coupled flagellar membrane adhesiveness. This effect is totally reversible, but only in the presence of new protein synthesis. The major flagellar protein modified by this pronase treatment is the faster migrating of the two high molecular weight glycoproteins; the other glycoprotein does not appear to be accessible to external proteolytic digestion. Loss and recovery of flagella surface binding sites for the specific antibody parallels the loss and recovery of the motility-coupled flagellar surface adhesiveness, as measured by the binding and translocation of polystyrene microspheres. These observations suggest, but do not prove, that the faster migrating of the major high molecular weight flagellar membrane glycoproteins may be the component which provides sites for substrate interaction and couples these sites to the cytoskeletal components responsible for force transduction.

Cell Membrane↗
PubMed1981

The randomized clinical trial: bias in analysis.

The realization that bias in patient selection may influence the results of clinical studies has helped to establish the randomized controlled clinical trial in medical research. However, bias can be equally important at other stages of a trial, especially at the time of analysis. Withdrawing patients from consideration in the analysis because of ineligibility on account of study entry criteria, lack of compliance to the protocol, or data of poor quality may be a source of systematic error. Examples to illustrate the possible consequences are taken from trials in the cardiovascular field. We recommended that reported study results should include outcome data from all subjects randomized in the group to which they were originally assigned.

Acute Disease↗