Advances in the production of chemicals by organelle compartmentalization in Saccharomyces cerevisiae / 生物工程学报

As a generally-recognized-as-safe microorganism, Saccharomyces cerevisiae is a widely studied chassis cell for the production of high-value or bulk chemicals in the field of synthetic biology. In recent years, a large number of synthesis pathways of chemicals have been established and optimized in S. cerevisiae by various metabolic engineering strategies, and the production of some chemicals have shown the potential of commercialization. As a eukaryote, S. cerevisiae has a complete inner membrane system and complex organelle compartments, and these compartments generally have higher concentrations of the precursor substrates (such as acetyl-CoA in mitochondria), or have sufficient enzymes, cofactors and energy which are required for the synthesis of some chemicals. These features may provide a more suitable physical and chemical environment for the biosynthesis of the targeted chemicals. However, the structural features of different organelles hinder the synthesis of specific chemicals. In order to ameliorate the efficiency of product biosynthesis, researchers have carried out a number of targeted modifications to the organelles grounded on an in-depth analysis of the characteristics of different organelles and the suitability of the production of target chemicals biosynthesis pathway to the organelles. In this review, the reconstruction and optimization of the biosynthesis pathways for production of chemicals by organelle mitochondria, peroxisome, golgi apparatus, endoplasmic reticulum, lipid droplets and vacuole compartmentalization in S. cerevisiae are reviewed in-depth. Current difficulties, challenges and future perspectives are highlighted.

Dynamic control of ERG20 expression to improve production of monoterpenes by engineering Saccharomyces cerevisiae / 中国中药杂志

Monoterpenes are widely used in cosmetics, food, medicine, agriculture and other fields. With the development of synthetic biology, it is considered as a potential way to create microbial cell factories to produce monoterpenes. Engineering Saccharomyces cerevisiae to produce monoterpenes has been a research hotspot in synthetic biology. In S. cerevisiae, the production of geranyl pyrophosphate(GPP) and farnesyl pyrophosphate(FPP) is catalyzed by a bifunctional enzyme farnesyl pyrophosphate synthetase(encoded by ERG20 gene) which is inclined to synthesize FPP essential for yeast growth. Therefore, reasonable control of FPP synthesis is the basis for efficient monoterpene synthesis in yeast cell factories. In order to achieve dynamic control from GPP to FPP biosynthesis in S. cerevisiae, we obtained a novel chassis strain HP001-pERG1-ERG20 by replacing the ERG20 promoter of the chassis strain HP001 with the promoter of cyclosqualene cyclase(ERG1) gene. Further, we reconstructed the metabolic pathway by using GPP and neryl diphosphate(NPP), cis-GPP as substrates in HP001-pERG1-ERG20. The yield of GPP-derived linalool increased by 42.5% to 7.6 mg·L~(-1), and that of NPP-derived nerol increased by 1 436.4% to 8.3 mg·L~(-1). This study provides a basis for the production of monoterpenes by microbial fermentation.

URA3 affects artemisinic acid production by an engineered Saccharomyces cerevisiae in pilot-scale fermentation / 生物工程学报

CRISPR/Cas9 has been widely used in engineering Saccharomyces cerevisiae for gene insertion, replacement and deletion due to its simplicity and high efficiency. The selectable markers of CRISPR/Cas9 systems are particularly useful for genome editing and Cas9-plasmids removing in yeast. In our previous research, GAL80 gene has been deleted by the plasmid pML104-mediated CRISPR/Cas9 system in an engineered yeast, in order to eliminate the requirement of galactose supplementation for induction. The maximum artemisinic acid production by engineered S. cerevisiae 1211-2 (740 mg/L) was comparable to that of the parental strain 1211 without galactose induction. Unfortunately, S. cerevisiae 1211-2 was inefficient in the utilization of the carbon source ethanol in the subsequent 50 L pilot fermentation experiment. The artemisinic acid yield in the engineered S. cerevisiae 1211-2 was only 20%-25% compared with that of S. cerevisiae 1211. The mutation of the selection marker URA3 was supposed to affect the growth and artemisinic acid production. A ura3 mutant was successfully restored by a recombinant plasmid pML104-KanMx4-u along with a 90 bp donor DNA, resulting in S. cerevisiae 1211-3. This mutant could grow normally in a fed-batch fermentor with mixed glucose and ethanol feeding, and the final artemisinic acid yield (> 20 g/L) was comparable to that of the parental strain S. cerevisiae 1211. In this study, an engineered yeast strain producing artemisinic acid without galactose induction was obtained. More importantly, it was the first report showing that the auxotrophic marker URA3 significantly affected artemisinic acid production in a pilot-scale fermentation with ethanol feeding, which provides a reference for the production of other natural products in yeast chassis.

Effect of RIM21 gene disruption on flocculation of lager yeast / 生物工程学报

Lager yeast is the most popular yeast strain used for beer production in China. The flocculation of yeast plays an important role in cell separation at the end of fermentation. Therefore, appropriately enhancing the flocculation capability of the lager yeast without affecting its fermentation performance would be desirable for beer industry. Our previous study showed that the defect of gene RIM21 might contribute to the enhanced flocculation capability of a lager yeast G03. To further investigate the role of the RIM21 gene in flocculation of strain G03, this study constructed a RIM21-deleted mutant strain G03-RIM21Δ through homologous recombination. Deletion of RIM21 improved the flocculation capability of strain G03 during wort fermentation at 11 °C without changing its fermentation performance significantly. The expression of FLO5, Lg-FLO1 and some other genes involved in cell wall integrity pathway were up-regulated in strain G03-RIM21Δ. In addition, the disruption of RIM21 enhanced resistance of yeast cells to cell wall inhibitors. These results provide a basis for elucidating the flocculation mechanism of lager yeast under low-temperature fermentation conditions.

Overexpression of a leucine transfer RNA gene tL(CAA)K improves the acetic acid tolerance of Saccharomyces cerevisiae / 生物工程学报

Acetic acid is a common inhibitor present in lignocellulosic hydrolysate. Development of acetic acid tolerant strains may improve the production of biofuels and bio-based chemicals using lignocellulosic biomass as raw materials. Current studies on stress tolerance of yeast Saccharomyces cerevisiae have mainly focused on transcription control, but the role of transfer RNA (tRNA) was rarely investigated. We found that some tRNA genes showed elevated transcription levels in a stress tolerant yeast strain. In this study, we further investigated the effects of overexpressing an arginine transfer RNA gene tR(ACG)D and a leucine transfer RNA gene tL(CAA)K on cell growth and ethanol production of S. cerevisiae BY4741 under acetic acid stress. The tL(CAA)K overexpression strain showed a better growth and a 29.41% higher ethanol productivity than that of the control strain. However, overexpression of tR(ACG)D showed negative influence on cell growth and ethanol production. Further studies revealed that the transcriptional levels of HAA1, MSN2, and MSN4, which encode transcription regulators related to stress tolerance, were up-regulated in tL(CAA)K overexpressed strain. This study provides an alternative strategy to develop robust yeast strains for cellulosic biorefinery, and also provides a basis for investigating how yeast stress tolerance is regulated by tRNA genes.

Higher alcohols metabolism by Saccharomyces cerevisiae: a mini review / 生物工程学报

Higher alcohols are one of the main by-products of Saccharomyces cerevisiae in brewing. High concentration of higher alcohols in alcoholic beverages easily causes headache, thirst and other symptoms after drinking. It is also the main reason for chronic drunkenness and difficulty in sobering up after intoxication. The main objective of this review is to present an overview of the flavor characteristics and metabolic pathways of higher alcohols as well as the application of mutagenesis breeding techniques in the regulation of higher alcohol metabolism in S. cerevisiae. In particular, we review the application of metabolic engineering technology in genetic modification of amino transferase, α-keto acid metabolism, acetate metabolism and carbon-nitrogen metabolism. Moreover, key challenges and future perspectives of realizing optimization of higher alcohols metabolism are discussed. This review is intended to provide a comprehensive understanding of metabolic regulation system of higher alcohols in S. cerevisiae and to provide insights into the rational development of the excellent industrial S. cerevisiae strains producing higher alcohols.

Comparison of interscalene brachial plexus block and intra-articular local anesthetic administration on postoperative pain management in arthroscopic shoulder surgery / Comparação de bloqueio do plexo braquial por via interescalênica e administração de anestésico local intra-articular no manejo da dor no pós-operatório de cirurgia artroscópica do ombro / Comparación de bloqueo del plexo braquial por vía interescalénica y administración de anestésico local intraarticular en el manejo del dolor en el postoperatorio de cirugía artroscópica del hombro

BACKGROUND AND OBJECTIVES: In this study, the aim was to compare postoperative analgesia effects of the administration of ultrasound-guided interscalene brachial plexus block and intra-articular bupivacaine carried out with bupivacaine. METHODS: In the first group of patients 20 mL 0.25% bupivacaine and ultrasound-guided interscalene brachial plexus block (ISPB) were applied, while 20 mL 0.25% bupivacaine was given via intra-articular (IA) administration to the second group patients after surgery. Patients in the third group were considered the control group and no block was performed. Patient-controlled analgesia (PCA) with morphine was used in all three groups for postoperative analgesia. RESULTS: In the ISPB group, morphine consumption in the periods between 0-4, 6-12 and 12-24 postoperative hours and total consumption within 24 h was lower than in the other two groups. Morphine consumption in the IA group was lower than in the control group in the period from 0 to 6 h and the same was true for total morphine consumption in 24 h. Postoperative VASr scores in the ISPB group were lower than both of the other groups in the first 2 h and lower than the control group in the 4th and 6th hours (p < 0.05). In the IA group, VASr and VASm scores in the 2nd, 4th and 6th hours were lower than in the control group (p < 0.05). CONCLUSION: Interscalene brachial plexus block was found to be more effective than intra-articular local anesthetic injection for postoperative analgesia. .

JUSTIFICATIVA E OBJETIVOS: Comparar os efeitos na analgesia no pós-operatório da administração de bloqueio do plexo braquial por via interescalênica guiado por ultrassom e bupivacaína intra-articular, feito com bupivacaína. MÉTODOS: No primeiro grupo de pacientes, 20 mL de bupivacaína a 0,25% e bloqueio do plexo braquial por via interescalênica guiado por ultrassom (BPBI) foram administrados, enquanto 20 mL de bupivacaína a 0,25% foram administrados por via intra-articular (IA) ao segundo grupo de pacientes após a cirurgia. Os pacientes do terceiro grupo foram considerados grupo controle e nenhum bloqueio foi feito. Analgesia controlada pelo paciente (ACP) com morfina foi usada nos três grupos para analgesia pós-operatória. RESULTADOS: No grupo BPBI, o consumo de morfina nos períodos entre 0-4, 6-12 e 12-24 horas após a cirurgia e o consumo total em 24 horas foram mais baixos do que nos outros dois grupos. O consumo de morfina no grupo IA foi menor do que no grupo controle no período de 0-6 horas, como também foi menor o consumo total de morfina em 24 horas. Os escores EVAr no pós-operatório do grupo BPBI foram menores do que os escores dos dois outros grupos nas primeiras duas horas e menores do que os do grupo controle nos períodos de 4 e 6 horas (p < 0,05). No grupo IA, os escores EVAr e EVAm nos períodos de 2, 4 e 6 horas foram menores do que no grupo controle (p < 0,05). CONCLUSÃO: O bloqueio do plexo braquial por via interescalênica mostrou ser mais eficaz do que a injeção intra-articular de anestésico local para analgesia pós-operatória. .

JUSTIFICACIÓN Y OBJETIVOS: En este estudio, nuestro objetivo fue comparar en el período postoperatorio los efectos analgésicos de la administración de la bupivacaína en el bloqueo del plexo braquial por vía interescalénica guiado por ecografía y bupivacaína intraarticular. MÉTODOS: En el primer grupo de pacientes se administraron 20 mL de bupivacaína al 0,25% y se llevó a cabo el bloqueo del plexo braquial por vía interescalénica (BPBI) guiado por ecografía, mientras que al segundo grupo de pacientes se le administraron 20 mL de bupivacaína al 0,25% por vía intraarticular (IA) tras la cirugía. Los pacientes del tercer grupo fueron considerados como grupo control y en ellos no se realizó ningún bloqueo. La analgesia controlada por el paciente con morfina se usó en los 3 grupos para la analgesia postoperatoria. RESULTADOS: En el grupo BPBI, el consumo de morfina en los períodos entre 0-4, 6-12 y 12-24 h del postoperatorio y el consumo total en 24 h fueron más bajos que en los otros 2 grupos. El consumo de morfina en el grupo IA fue menor que en el grupo control en el período de 0-6 h, como también fue menor el consumo total de morfina en 24 h. Las puntuaciones EVAr en el postoperatorio del grupo BPBI fueron menores que las de los otros 2 grupos en las primeras 2 h y menores que los del grupo control en los períodos de 4 y 6 h (p < 0,05). En el grupo IA, las puntuaciones EVAr y EVAm en los períodos de 2, 4 y 6 h fueron menores que en el grupo control (p < 0,05). CONCLUSIÓN: El BPBI mostró ser más eficaz que la inyección intraarticular de anestésico local para analgesia postoperatoria. .

Pontos de venda de alimentos e associação com sobrepeso/obesidade em escolares de Florianópolis, Santa Catarina, Brasil / Retail food outlets and the association with overweight/obesity in schoolchildren from Florianópolis, Santa Catarina State, Brazil / Puntos de venta de alimentos y asociación con sobrepeso/obesidad en escolares de Florianópolis, Santa Catarina, Brasil

O estudo descreve os pontos de venda de alimentos e sua associação com sobrepeso/obesidade em escolares de Florianópolis, Santa Catarina, Brasil. Desenho transversal com amostra probabilística de 2.506 escolares de escolas públicas (n = 19) e privadas (n = 11). O sobrepeso/obesidade foi classificado pela referência da Organização Mundial da Saúde de 2007. Foram realizadas análises brutas e ajustadas por meio de regressão de Poisson. A prevalência de sobrepeso/obesidade foi de 34,2%. Na rede pública, foram verificados 19,6% de sobrepeso e 13,5% de obesidade. Na rede privada, observaram-se 22,4% de sobrepeso e 11,1% de obesidade. Na rede pública, foi encontrada associação entre sobrepeso/obesidade e utilização da padaria (p = 0,004). Na rede privada, observou-se que os escolares de famílias que utilizaram o supermercado apresentaram 26% menos de sobrepeso/obesidade do que os escolares que não utilizam esses pontos de venda de alimentos (p = 0,003). Os dados encontrados evidenciam a existência de associação entre a utilização de alguns tipos de pontos de venda de alimentos (supermercado e padaria) e a prevalência de sobrepeso/obesidade na população escolar.

The study analyzes retail food outlets and their association with overweight/obesity in schoolchildren from Florianópolis, Santa Catarina State, Brazil. The study used a cross-sectional design with a random sample of 2,506 schoolchildren from public (n = 19) and private schools (n = 11). Overweight and obesity were classified according to World Health Organization guidelines for 2007, and crude and adjusted analyses were performed using Poisson regression. Prevalence of overweight/obesity was 34.2%. In public schools, 19.6% of the children were overweight and 13.5% were obese, as compared to 22.4% and 11.1% in private schools. An association was found in the public school system between overweight/obesity and the use of bakeries for food purchases (p = 0.004). In the private school system, children of families that bought groceries at the supermarket showed 26% less overweight/obesity compared to those who did not (p = 0.003). The data show an association between some types of food outlets (supermarkets and bakeries) and prevalence of overweight/obesity in the school-age population.

El estudio describe los puntos de venta de alimentos y su asociación con el sobrepeso/obesidad en escolares de Florianópolis, Santa Catarina, Brasil. Se trata de un estudio transversal con una muestra aleatoria de 2.506 escolares de las escuelas públicas (n = 19) y privadas (n = 11). El sobrepeso/obesidad se clasifica, en función de la OMS en 2007, con análisis ajustados y crudos que se realizaron mediante la regresión de Poisson. La prevalencia de sobrepeso/obesidad fue de un 34,2%. En el sistema público el resultado fue de un 19,6% sobrepeso y un 13,5% obesidad. En el privado se observó un 22,4% de sobrepeso y 11,1% obesidad. En el primero se encontró una correlación entre el sobrepeso/obesidad y el consumo de bollería (p = 0,004). En las escuelas privadas se observó que los escolares de familias que habían utilizado el supermercado tenían un 26% menos de sobrepeso/ obesidad que los niños en edad escolar que no utilizaron este punto de venta de alimentos (p = 0,003). En el momento del estudio existe una asociación entre el uso de algunos tipos de punto de venta de alimentos (supermercado y panadería) y la prevalencia de sobrepeso/obesidad en escolares.

Evaluación del perfil de eficacia y seguridad de vildagliptina en vida real de pacientes chilenos con diabetes mellitus tipo 2 / Safety and efficacy of Vildagliptin in real life Chilean diabetic patients

Background: Vildagliptin is a dipeptidyl peptidase IV inhibitor (DPP4i). Its efficacy and safety of DPP4i in Chilean real life type 2 diabetic (T2D) patients is not well known. Aim: To assess the safety profile and effectiveness of 12 weeks of treatment with Vildagliptin for glycemic control in T2D Chilean patients with a poor glycemic control. Patients and Methods: Retrospective assessment of the effects of Vildagliptin treatment during 12 weeks in 103 T2D patients aged 29 to 92 years (47% males). The main outcomes were changes in glycosylated hemoglobin and the occurrence of adverse effects. Results: After 12 weeks of Vildagliptin use, glycosylated hemoglobin decreased from 8.3 ± 1.4 to 7.2 ± 1.1% (p < 0.01). Fasting plasma glucose and the number of hypoglycemic events also decreased significantly. No significant weight change was observed. The treatment had good compliance, tolerance and patient satisfaction. Conclusions: Vildagliptin treatment reduced glycosylated hemoglobin by 1.1% and was well tolerated in this group of diabetic patients.

Yeast HXK2 gene reverts glucose regulation mutation of penicillin biosynthesis in P. chrysogenum

The mutant Penicillium chrysogenum strain dogR5, derived from strain AS-P-78, does not respond to glucose regulation of penicillin biosynthesis and β-galactosidase, and is partially deficient in D-glucose phosphorilating activity. We have transformed strain dogR5 with the (hexokinase) hxk2 gene from Saccharomyces cerevisiae. Transformants recovered glucose control of penicillin biosynthesis in different degrees, and acquired a hexokinase (fructose phosphorylating) activity absent in strains AS- P-78 and dogR5. Interestingly, they also recovered glucose regulation of β-galactosidase. On the other hand, glucokinase activity was affected in different ways in the transformants; one of which showed a lower activity than the parental dogR5, but normal glucose regulation of penicillin biosynthesis. Our results show that Penicillium chrysogenum AS-P-78 and dogR5 strains lack hexokinase, and suggest that an enzyme with glucokinase activity is involved in glucose regulation of penicillin biosynthesis and β-galactosidase, thus signaling glucose in both primary and secondary metabolism; however, catalytic and signaling activities seem to be independent.

DNA repair by polymerase delta in Saccharomyces cerevisiae is not controlled by the proliferating cell nuclear antigen-like Rad17/Mec3/Ddc1complex

DNA damage activates several mechanisms such as DNA repair and cell cycle checkpoints. The Saccharomyces cerevisiae heterotrimeric checkpoint clamp consisting of the Rad17, Mec3 and Ddc1 subunits is an early response factor to DNA damage and activates checkpoints. This complex is structurally similar to the proliferating cell nuclear antigen (PCNA), which serves as a sliding clamp platform for DNA replication. Growing evidence suggests that PCNA-like complexes play a major role in DNA repair as they have been shown to interact with and stimulate several proteins, including specialized DNA polymerases. With the aim of extending our knowledge concerning the link between checkpoint activation and DNA repair, we tested the possibility of a functional interaction between the Rad17/Mec3/Ddc1 complex and the replicative DNA polymerases alpha, delta and epsilon. The analysis of sensitivity response of single and double mutants to UVC and 8-MOP + UVA-induced DNA damage suggests that the PCNA-like component Mec3p of S. cerevisiae neither relies on nor competes with the third subunit of DNA polymerase delta, Pol32p, for lesion removal. No enhanced sensitivity was observed when inactivating components of DNA polymerases alpha and epsilon in the absence of Mec3p. The hypersensitivity of pol32delta to photoactivated 8-MOP suggests that the replicative DNA polymerase delta also participates in the repair of mono- and bi-functional DNA adducts. Repair of UVC and 8-MOP + UVA-induced DNA damage via polymerase delta thus occurs independent of the Rad17/Mec3/Ddc1 checkpoint clamp.

Identification of the divergent calmodulin binding motif in yeast Ssb1/Hsp75 protein and in other HSP70 family members

Yeast soluble proteins were fractionated by calmodulin-agarose affinity chromatography and the Ca2+/calmodulin-binding proteins were analyzed by SDS-PAGE. One prominent protein of 66 kDa was excised from the gel, digested with trypsin and the masses of the resultant fragments were determined by MALDI/MS. Twenty-one of 38 monoisotopic peptide masses obtained after tryptic digestion were matched to the heat shock protein Ssb1/Hsp75, covering 37 percent of its sequence. Computational analysis of the primary structure of Ssb1/Hsp75 identified a unique potential amphipathic alpha-helix in its N-terminal ATPase domain with features of target regions for Ca2+/calmodulin binding. This region, which shares 89 percent similarity to the experimentally determined calmodulin-binding domain from mouse, Hsc70, is conserved in near half of the 113 members of the HSP70 family investigated, from yeast to plant and animals. Based on the sequence of this region, phylogenetic analysis grouped the HSP70s in three distinct branches. Two of them comprise the non-calmodulin binding Hsp70s BIP/GR78, a subfamily of eukaryotic HSP70 localized in the endoplasmic reticulum, and DnaK, a subfamily of prokaryotic HSP70. A third heterogeneous group is formed by eukaryotic cytosolic HSP70s containing the new calmodulin-binding motif and other cytosolic HSP70s whose sequences do not conform to those conserved motif, indicating that not all eukaryotic cytosolic Hsp70s are target for calmodulin regulation. Furthermore, the calmodulin-binding domain found in eukaryotic HSP70s is also the target for binding of Bag-1 - an enhancer of ADP/ATP exchange activity of Hsp70s. A model in which calmodulin displaces Bag-1 and modulates Ssb1/Hsp75 chaperone activity is discussed.

Functional complementation of a yeast knockout strain by Schistosoma mansoni Rho1 GTPase in the presence of caffeine, an agent that affects mutants defective in the protein kinase C signal transduction pathway

In a previous study, the Schistosoma mansoni Rho1 protein was able to complement Rho1 null mutant Saccharomyces cerevisiae cells at restrictive temperatures and under osmotic stress (low calcium concentration) better than the human homologue (RhoA). It is known that under osmotic stress, the S. cerevisiae Rho1 triggers two distinct pathways: activation of the membrane 1,3-beta-glucan synthase enzymatic complex and activation of the protein kinase C1 signal transduction pathway, promoting the transcription of response genes. In the present work the SmRho1 protein and its mutants smrho1E97P, smrho1L101T, and smrho1E97P, L101T were used to try to clarify the basis for the differential complementation of Rho1 knockout yeast strain by the human and S. mansoni genes. Experiments of functional complementation in the presence of caffeine and in the presence of the osmotic regulator sorbitol were conducted. SmRho1 and its mutants showed a differential complementation of the yeast cells in the presence of caffeine, since smrho1E97P and smrho1E97P, L101T mutants showed a delay in the growth when compared to the yeast complemented with the wild type SmRho1. However, in the presence of sorbitol and caffeine the wild type SmRho1 and mutants showed a similar complementation phenotype, as they allowed yeast growth in all caffeine concentrations tested.

Regulation of trehalose metabolism by Adox and AdoMet in Saccharomyces cerevisiae.

Effect of a potent methylation inhibitor oxidized adenosine (Adox), and a universal methyl group donor S-adenosyl-L-methionine (AdoMet) on trehalose metabolism was studied in two haploids of S. cerevisiae of mating types MATalpha, met3 (6460 -8D) and MATa, leu2, ura3, his4 (8534 -10A). Trehalose level decreased in presence of Adox in both strains. Both neutral trehalase (NT) and trehalose-6-phosphate (tre-6-p) synthase activities increased in presence of Adox in -8D strain. Decrease in trehalose level in -8D thus could not be explained in the light of increased tre-6-p synthase activity; however, it could be correlated with increased NT activity. In strain -10A, NT activity was reduced in presence of Adox while tre-6-p synthase activity increased. Enzyme activity profiles in -10A thus do not explain the reduced trehalose level on Adox treatment. Effect of AdoMet was not very prominent in either strain, though in -8D a small increase in trehalose level was seen on treatment. Intracellular AdoMet level of untreated cells of -10A was seen to be almost six times higher than that of -8D. Further, AdoMet treatment caused increase in its level compared to untreated cells, suggesting AdoMet uptake. No effect of either compound was seen on acid trehalase (AT) activity in any strain. The results suggest that there was a possible effect of demethylation on trehalose metabolism (particularly in the synthetic direction) in both strains, though effect of methylation was not very prominent, the reason for which is not very clear.

The transcriptional activator GAL4-VP16 regulates the intra-molecular interactions of the TATA-binding protein.

Binding characteristics of yeast TATA-binding protein (yTBP) over five oligomers having different TATA variants and lacking a UASGAL, showed that TATA-binding protein (TBP)-TATA complex gets stabilized in the presence of the acidic activator GAL4-VP16. Activator also greatly suppressed the non-specific TBP-DNA complex formation. The effects were more pronounced over weaker TATA boxes. Activator also reduced the TBP dimer levels both in vitro and in vivo, suggesting the dimer may be a direct target of transcriptional activators. The transcriptional activator facilitated the dimer to monomer transition and activated monomers further to help TBP bind even the weaker TATA boxes stably. The overall stimulatory effect of the GAL4-VP16 on the TBP-TATA complex formation resembles the known effects of removal of the N-terminus of TBP on its activity, suggesting that the activator directly targets the N-terminus of TBP and facilitates its binding to the TATA box.

GAL4 causes developmental defects and apoptosis when expressed in the developing eye of Drosophila melanogaster

The UAS/GAL4 ectopic expression system is widely used in Drosophila melanogaster for the overexpression of transgenes. This system operates under the assumption that the yeast transcription factor, GAL4, is inactive in D. melanogaster. Thus, GAL4 can be expressed under the control of D. melanogaster -specific promoters with little effect upon the organism. We have shown that expression of GAL4 in the developing eye under the control of the glass multiple reporter (GMR) promoter element does have an effect on eye development. Although GMR-GAL4 heterozygotes appear normal when raised at 25 degrees C, the homozygotes have a highly disorganized ommatidial array. In addition, the levels of apoptosis in the third-instar larval eye imaginal disc (where GAL4 is expressed) are slightly higher in GMR-GAL4 heterozygotes, and much higher in GMR-GAL4 homozygotes when compared to wild type discs. The morphological eye defects caused by GMR-GAL4 are significantly enhanced when flies are raised at 29 degrees C (presumably due to the higher activity of GAL4 at this temperature); however, the levels of apoptosis appear to be similar at these two temperatures. Taken together, these data suggest that GAL4 can have adverse effects on D. melanogaster development, especially at high expression levels. In addition, GAL4 appears to induce apoptosis even in the absence of any visible morphological defects. Thus, despite the benefits of the UAS/GAL4 ectopic expression system, one must use caution in the design and interpretation of experiments