Frequent derepression of G6PD and HPRT on the marsupial inactive X chromosome associated with cell proliferation in vitro

X chromosome dosage compensation in Marsupials is like that in eutherian mammals except that the paternal X chromosome is always inactive, and silence of this chromosome is not well maintained. We previously showed that the unstable inactivation of the paternal G6PD allele is associated with the lack of DNA methylation in the 5' CpG cluster. Even though this CpG island is unmethylated, the paternal allele (marked by an enzyme variant) is at least partially and often severely repressed in most tissues of the opossum, so that factors other than methylation must inactivate the locus. Here we report that when cell cultures are established from these tissues, the silent G6PD locus is depressed. Although often complete, the extent of derepression differs among tissues and within different cell types in the same tissue, and is not accompanied by obvious changes in the pattern of chromosome replication. Studies of the HPRT locus in these cells show that the paternal HPRT allele also derepresses in cultured cells. These observations suggest that without DNA methylation to maintain the silence of the locus, tissue or cell-specific factors act to repress the silent locus, but are unable to maintain inactivity through cell division, or are lost as cells proliferate in culture.     

Increased heterologous production of the antitumoral polyketide mithramycin A by engineered Streptomyces lividans TK24 strains

Mithramycin A is an antitumor compound used for treatment of several types of cancer including chronic and acute myeloid leukemia, testicular carcinoma, hypercalcemia and Paget’s disease. Selective modifications of this molecule by combinatorial biosynthesis and biocatalysis opened the possibility to produce mithramycin analogues with improved properties that are currently under preclinical development. The mithramycin A biosynthetic gene cluster from Streptomyces argillaceus ATCC12956 was cloned by transformation assisted recombination in Saccharomyces cerevisiae and heterologous expression in Streptomyces lividans TK24 was evaluated. Mithramycin A was efficiently produced by S. lividans TK24 under standard fermentation conditions. To improve the yield of heterologously produced mithramycin A, a collection of derivative strains of S. lividans TK24 were constructed by sequential deletion of known potentially interfering secondary metabolite gene clusters using a protocol based on the positive selection of double crossover events with blue pigment indigoidine-producing gene. Mithramycin A production was evaluated in these S. lividans strains and substantially improved mithramycin A production was observed depending on the deleted gene clusters. A collection of S. lividans strains suitable for heterologous expression of actinomycetes secondary metabolites were generated and efficient production of mithramycin A with yields close to 3 g/L, under the tested fermentation conditions was achieved using these optimized collection of strains.

     

A Centipede Toxin Family Defines an Ancient Class of CSαβ Defensins

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Investigation of the mechanism of the action of dimethyllaurylbenzyl-ammonium chloride (ajatin) on rough and smooth forms of yeast cells

Ajatin эффект от потреблен ия кислорода в присутствии некото рых промежуточных и продукция была Гликолиз расследование вмест е с эффект iodoacetic кислоты, для того что бы пролить свет еще выше чувствительность грубый формы дрожжей для Ajatin и объяснить синергический дейст вия Ajatin и iodoacetic кислоты в присутстви и глюкозы. Было установлено, что окисление этанола и ацетата в грубой форме distiller дрожжи гораздо боле е чувствительны для действий Ajatin чем окисление глюкозы, в то время как в виде гладких разница в чувствительности ме жду этими двух процессов меньш е. Потребление кислорода в присутст вии этанола или ацетата в качестве субстрата значитель но сдерживается путем iodoacetic кислоты в виде гладких, но не зависит от этого ингибитора в грубой форме. На основе результато в и данных в литературе метаболизма гладких и грубые формы дрожже й обсуждается и Причины синергическ ий действия Ajatin и iodoacetic кислоты на потребление кислоро да в присутствии глюк озы принимаются вверх. Она представляет интерес для обнаружи ть, что окислительные проце ссы не мешает arsenite, относительно устойчив к Ajatin с тем, что в присутстви и arsenite разница в чувствительности дв ух формах дрожжей в действие по чти Ajatin исчезает.     

Intensity of photosynthesis and chlorophyll content as related to leaf age inNicotiana Sanderae hort

U r?zně starých list? v listové r??ici 90 a? 110 denních rostlin Nicotiana sanderae hort. byly sledovány rozdály v intensitě ?isté fotosynthesy a v obsahu chlorofylu (a + b). Ke stanovení intensity fotosynthesy bylo pou?ito dvou odli?ných metod, a to váhového stanovení p?ír?stku su?iny podle Barto?e, KubÍna a ?et-lÍka (1960) a gazometrického stanovení infra?erveným analyzátorem CO₂. Nejvy??í intensitu fotosynthesy i nejvy??í obsah chlorofylu (vzhledem k plo?e listové) mají mladé, ale ji? dob?e rozvinuté listy, tj. t?etí a? ?tvrté od vrcholu (prvním listem se rozumí list o plo?e asi 20 cm²). Tyto listy nazýváme ?fotosyntheticky dospělými“. Listy nejmlad?í a zejména pak listy star?í mají intensitu fotosynthesy i obsah chlorofylu ni??í; u nejstar?ích list? je intensita fotosynthesy prakticky nulová. Intensita fotosynthesy i obsah chlorofylu se během vývoje mění: jejich momentální rozdíly u list? v genetické spirále jsou z?ejmě shodné s jejich změnami v ontogenesi listu. Pokles intensity fotosynthesy p?i stárnutí list? je rychlej?í ne? pokles obsahu chlorofylu. P?i ur?itém obsahu chlorofylu (tj. asi 2,25 a? 2,45 mg/dm²) klesá intensita ?isté fotosynthesy k nule. Intensita fotosynthesy je v lineárním vztahu k mno?ství chlorofylu (p?i p?epo?tu na plo?nou jednotku), a to nezávisle na poloze listu v genetické spirále. Obě pou?ité metody ke stanovení intensity fotosynthesy poskytly obdobné výsledky.     

New Methods of Chromatographic Separation of Gibberellins A1 and A3

Biologia Plantarum - New Chromatographic methods, chromatography in centrifugal field and thin-layer chromatography on alumina, were used for separating physiologically active gibberellins A1 and...     

Occurrence of cytochromes in R and S yeast mutants of the genusSaccharomyces

Visible region of an absorption spectrum was followed in cells of original strains and of rough mutants ofSaccharomyces cerevisiae andS. cerevisiae var.ellipsoideus. It was found that there are no substantial differences in relative content of cytochromesb andc in aerobically grown rough and smooth yeast forms, in spite of the fact that both forms differ substantially in the metabolic oxygen quotient. If the cytochromes present were not reduced in washed cells by dithionite or by substrate addition, the rough forms exhibited a lower cytochrome b:c ratio than the smooth forms. Under anaerobic conditions of cultivation, the rough forms retained a typical aerobic spectrum, lacking, however, the cytochromea and a₃ band; the ratio of cytochromesb andc was changed in favour of cytochromeb (from the original 1.7: 1 up to 3.4: 1). The inability of the rough mutants to produce anaerobic cytochrome spectrum represented by cytochrome b₁ was connected with their inability to reproduce under anaerobic conditions.     

Investigating species boundaries using DNA and morphology in the mite <Emphasis Type="Italic">Tyrophagus curvipenis</Emphasis> (Acari: Acaridae), an emerging invasive pest,with a molecular phylogeny of the genus <Emphasis Type="Italic">Tyrophagus</Emphasis>

Mites of the genus Tyrophagus (Acari: Acaridae) are among the most widespread and common mites, inhabiting diverse natural and anthropogenic habitats. Some species are pests of agricultural products and stored food and/or live in house dust, causing allergies to humans. We sequenced 1.2 kb of the mitochondrial COI gene for 38 individuals belonging to seven species of Tyrophagus, including T. curvipenis, T. putrescentiae, T. fanetzhangorum, T. longior, T. perniciosus, and T. cf. similis. Molecular phylogenetic analyses (1) recovered two major clades corresponding to the presence or absence of eyespots, and (2) separated all included morphological species. Tyrophagus curvipenis and T. putrescentiae had the lowest between-species genetic distances (range, mean?±?SD): 14.20–16.30, 15.17?±?0.40 (K2P). The highest within-species variation was found in T. putrescentiae 0.00–4.33, 1.78?±?1.44 (K2P). In this species, we recovered two distinct groups; however, no geographical or ecological dissimilarities were observed between them. Based on our analyses, we document important morphological differences between T. curvipenis and T. putrescentiae. For the first time, we record the occurrence of T. curvipenis in the New World and suggest that it may be an emerging pest as it is currently spreading in agricultural produce.     

Antibody drug conjugates of cleavable amino-alkyl and aryl maytansinoids

Natural products have been used for many medicinal purposes for centuries. Antibody drug conjugates (ADCs) have utilized this rich source of small molecule therapeutics to produce several clinically useful treatments. ADCs based on the natural product maytansine have been successful clinically. The authors further the utility of the anti-cancer natural product maytansine by developing efficacious payloads and linker-payloads for conjugating to antibodies. The success of our approach was realized in the EGFRvIII targeting ADC EGFRvIII-16. The ADC was able to regress tumors in 2 tumor models (U251/EGFRvIII and MMT/EGFRvIII). When compared to a positive control ADC, the efficacy observed was similar or improved while the isotype control ADCs had no effect.