Metabolic status of temperature induced swollen conidia ofAspergillus nidulans

Summary There is an active synthesis of DNA, RNA, protein, and carbohydrate in conidia incubated at 48°C. DNA increases more or less 3 times; while RNA, protein and carbohydrate are synthesized at a much faster rate. Conidia do not germinate at this temperature.Acknowledgments. Grateful thanks are due to Professor B. M. Johri for valuable suggestions. R. K. S. acknowledges with thanks a Senior Research Fellowship of the Council of Scientific and Industrial Research, New Delhi.     

Stimulation of ribonuclease activity and its isoenzymes in germinating seeds of cowpea (Vigna sinensis) by gibberellic acid and adenosine-3',5-cyclic monophosphate.

Application of GA3 and cyclic AMP to cowpea seedings caused a 2-3 fold stimulation of RNAase activity, together with the augmentation of RNAase isoenzymes. Inhibitor studies indicated the requirement of fresh RNA and protein synthesis for enzyme stimulation.     

RNA recognition by double-stranded RNA binding domains: a matter of shape and sequence

The double-stranded RNA binding domain (dsRBD) is a small protein domain of 65–70 amino acids adopting an αβββα fold, whose central property is to bind to double-stranded RNA (dsRNA). This domain is present in proteins implicated in many aspects of cellular life, including antiviral response, RNA editing, RNA processing, RNA transport and, last but not least, RNA silencing. Even though proteins containing dsRBDs can bind to very specific dsRNA targets in vivo, the binding of dsRBDs to dsRNA is commonly believed to be shape-dependent rather than sequence-specific. Interestingly, recent structural information on dsRNA recognition by dsRBDs opens the possibility that this domain performs a direct readout of RNA sequence in the minor groove, allowing a global reconsideration of the principles describing dsRNA recognition by dsRBDs. We review in this article the current structural and molecular knowledge on dsRBDs, emphasizing the intricate relationship between the amino acid sequence, the structure of the domain and its RNA recognition capacity. We especially focus on the molecular determinants of dsRNA recognition and describe how sequence discrimination can be achieved by this type of domain.     

Stimulation of ribonuclease activity and its isoenzymes in germinating seeds of cowpea (Vigna sinensis) by gibberellic acid and adenosine-3′,5′-cyclic monophosphate

Summary Application of GA₃ and cyclic AMP to cowpea seedlings caused a 2–3 fold stimulation of RNAase activity, together with the augmentation of RNAase isoenzymes. Inhibitor studies indicated the requirement of fresh RNA and protein synthesis for enzyme stimulation.     

Protein synthesis during germination of heterothallic yeast ascospores.

Protein synthesis during ascospore germination of the heterothallic Saccharomyces cerevisiae strain AP-3 was investigated. Protein synthesis in the germinating ascospores appeared to begin approximately 20 min following glucose initiation. Since RNA synthesis did not start until approximately 70 min after the onset of germination, strain AP-3 ascospores must contain RNA which is ready for immediate translation. Both trehalase and glyceraldehyde-3-phosphate dehydrogenase activities were found to be affected by the onset of germination. Trehalase activity was found to increase severalfold following 60 min of spore germination but remained relatively constant over the subsequent 120 min examined. Dehydrogenase activity was not detectable in AP-3 ascospores but was measurable in germinating ascospores.     

Protein synthesis during germination of heterothallic yeast ascospores

Protein synthesis during ascospore germination of the heterothallicSaccharomyces cerevisiae strain AP-3 was investigated. Protein synthesis in the germinating ascospores appeared to begin approximately 20 min following glucose initiation. Since RNA synthesis did not start until approximately 70 min after the onset of germination, strain AP-3 ascospores must contain RNA which is ready for immediate translation. Both trehalase and glyceraldehyde-3-phosphate dehydrogenase activities were found to be affected by the onset of germination. Trehalase activity was found to increase severalfold following 60 min of spore germination but remained relatively constant over the subsequent 120 min examined. Dehydrogenase activity was not detectable in AP-3 ascospores but was measurable in germinating ascospores.     

Lokalisation zusätzlicher RNS-Synthese in Trypsin-behandelten Riesenchromosomen vonChironomus thummi

Summary After injection of buffered trypsin into nuclei of salivary gland cells ofChironomus thummi, the existing puffs in the giant chromosomes are enlarged. Autoradiography shows an increase in RNA synthesis of approximately 3-fold in these puffs. It is argued that histones in puffed chromosome segments are in a structural state that renders them unable to prevent RNA synthesis and at the same time causes them to be attacked earlier by trypsin.     

Arginase expression in peritoneal macrophages and increase in circulating polyamine levels in mice infected with Schistosoma mansoni

We investigated the nitric oxide (NO) synthase and arginase pathways in resident peritoneal macrophages of mice infected with the tropical parasite Schistosoma mansoni. The two enzymes may have opposite effects, insofar as NO may be involved in the killing of the parasite whereas arginase may stimulate parasite growth via polyamine synthesis. We determined the effects of the infection on the expression and activity of the two enzymes in macrophages, before and after cytokine activation. Cells from infected mice expressed the hepatic type I arginase, whereas in control cells, the enzyme was expressed only after cytokine activation, as were NO synthase II and type II arginase in both groups of cells. Moreover, we found that in infected mice, arginase expression in macrophages was associated with a ten fold increase in the concentration of circulating ornithine-derived polyamines. This may be of pathological importance, since parasitic helminths are though to be dependent on their hosts for the uptake and interconversion of polyamines. Received 13 March 2001; received after revision 4 May 2001; accepted 7 June 2001     

Experimentelle Untersuchungen zum Wirkungsmechanismus der beiden entwicklungsphysiologisch aktiven Fraktionen des «Gehirnhormons» der Insekten (Aktivationsfaktor I und II) auf die Prothoracaldrüse

Summary 2 prothoracotropical factors (activation factor I and II) have been obtained by gel filtration techniques from brains and corpora cardiaca of the cockroachPeriplaneta americana. In contrast to activation factor II, activation factor I caused significant influence of RNA synthesis. The RNA pattern of prothoracic glands stimulated by activation factor I as demonstrated by polyacrylamide gel electrophoresis consists of different kinds of RNA. Short time incubation revealed effects on sRNA synthesis, while long time incubation demonstrated predominantly increase of ribosomal RNA synthesis. Measurements of the membrane potential of the prothoracic gland cells of the wax mothGalleria mellonella indicated an increase by activation factor II; activation factor I was without any visible effect. Our results demonstrate for the first time that the two activation factors induce different effects at cellular level.

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Für technische Unterstützung danken wir FräuleinA. Zinsser und FrauR. Meissner.

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Durchgeführt mit Mitteln des Ministeriums für Wissenschaft und Technik und mit Unterstützung durch die Sächsische Akademie der Wissenschaften zu Leipzig.     

Effects of biotin deficiency on serum proteins and plasma amino acids.

In biotin-deficient rats, a decrease of total proteins, attributable to a decrease of albumin and alpha1-globulin fractions, a decrease of the pre-beta-lipoproteins and an increase of the alpha-lipoproteins, was observed, together with a rise of total amino acids. Such a situation may be related to the influence of biotin on the synthesis of RNA and proteins.     

Studies on stable and during early imbibition phases synthesized poly(A)-RNA of Agrostemma githago embryos (author's transl)]

RNA isolated from dry embryos of Agrostemma githago seeds contains poly(A)-sequences, but in very small amounts. In the early phase of imbibition, an intensive synthesis of poly(A)-containing RNA is brought about. The importance of this synthesis of poly(A)-RNA is discussed.     

Primary nucleolus and amphinucleoli in the oocytes ofPatella coerulea L. (Moll. Gast.)

Summary Electron microscope observations show in the primary nucleolus some granulations with dimensions less (70 Å) than those of the amphinucleoli (90 Å). Even though the primary nucleolus has a high RNA content, this has not a very active turnover except at the periphery, probably in relation to the emission of daughter-nucleoli. The amphinucleoli, even though they do not have RNA which is cytochemically discloseable, possess, however, RNA at a very high rate of turnover.     

Contrasting effects of RNA and protein synthesis blocking on natural and lectin-dependent cell-mediated cytotoxicity against adherent HEp-2 cells

In this study, earlier observations concerning the independence of both natural (NCMC) and lectin-dependent cell-mediated cytotoxicity (LDCC) from DNA synthesis have been confirmed. In addition, blocking of RNA synthesis by actinomycin D and of protein synthesis, reversibly by puromycin (PM) and irreversibly by emetine (EM) had different effects on NCMC and LDCC against 3H-thymidine-prelabeled HEp-2 target cells. Similarly to the Con A-induced proliferation of lymphocytes, LDCC activity was also inhibited by blocking of RNA and protein synthesis. NCMC to HEp-2 target cells was not affected by blocking of RNA synthesis, while both PM and EM strongly enhanced NCMC activity.     

Contrasting effects of RNA and protein synthesis blocking on natural and lectin-dependent cell-mediated cytotoxicity against adherent HEp-2 cells

Summary In this study, earlier observations^2,9 concerning the independence of both natural (NCMC) and lectin-dependent cell-mediated cytotoxicity (LDCC) from DNA synthesis have been confirmed. In addition, blocking of RNA synthesis by actinomycin D and of protein synthesis, reversibly by puromycin (PM) and irreversibly by emetine (EM) had different effects on NCMC and LDCC against³H-thymidine-prelabeled HEp-2 target cells. Similarly to the Con A-induced proliferation of lymphocytes, LDCC activity was also inhibited by blocking of RNA and protein synthesis. NCMC to HEp-2 target cells was not affected by blocking of RNA synthesis, while both PM and EM strongly enhanced NCMC activity.     

Functions of nuclear bodies as revealed by ultrastructural autoradiography and cytochemistry

Summary The simple nuclear body containing a few RNA particles appears through the nuclear pores in the cytoplasm, originating from the nucleolus. The complex nuclear body consisting mainly of RNA components is highly active in the incorporation of RNA precursors. Accordingly, the appearance of nuclear bodies may be related either to transport to the cytoplasm of nucleolar components or to the enhancement of rRNA synthesis.     

Autoradiographic localization of RNA synthesis in vitro during oogenesis in Parascaris equorum]

Technical elaboration of in vitro incubation of Parascaris equorum gonads with 3H-Uridine has permitted, for the first time, the study of RNA synthesis during oogenesis along the whole gonadic tube. In germ cells, oocytes in diakinesis (oviduct) and in division of maturation (uterus) show no label. On the contrary oogonia and growing oocytes in ovary are labelled. RNA synthesis is always detected in all parietal cells but is more active in oviduct and uterus where the gonadic wall is particularly developed.     

High salt effect on RNA synthesis in Krebs ascites tumor cells

The incubation of Krebs ascites tumor cells in medium with a high salt concentration resulted in a partial inhibition of nuclear RNA synthesis. The residual RNA polymerase activity in such nuclei was only slightly inhibited by low concentrations (50 nM) of alpha-amanitin. This finding suggested an inhibition of RNA polymerase II activity under conditions of medium hypertonicity. Indeed, RNA polymerase II, isolated from the nuclei of cells exposed to hypertonicity, revealed only half of the control activity. On the other hand, RNA polymerase I was not affected by hypertonicity. Moreover, chromatin fractions isolated from cells incubated in hypertonic or isotonic medium were equally template-active in RNA synthesis.     

Satellite RNA (RNA3) of tomato black ring virus is found with one of the 2 major RNAs (RNA2) in a new capsid nucleoprotein]

Tomato Black Ring Virus (TBRV) like other NEPOviruses posseses two nucleoproteins M and B and two major RNAs, RNA1 and RNA2 respectively distributed in B and M. A new nucleoprotein has just been discovered and comprises one molecule of RNA2 associated with one molecule of RNA3. RNA3 is a small RNA of molecular weight 500,000 d considered to be a satellite RNA. Its level appears to depend on the infection stage, local or systemic. RNA3 is able to modify the relative proportions of nucleoproteins M and B and their respective RNAs. The satellite RNA, might be part of the genome and represent a monocistronic mRNA for protein capsid synthesis. However it seems perhaps more tempting to correlate TBRV-RNA3 with satellite RNA5 of certain strains of Cucumber mosaic virus.     

Modulating RNA structure and catalysis: lessons from small cleaving ribozymes

RNA is a key molecule in life, and comprehending its structure/function relationships is a crucial step towards a more complete understanding of molecular biology. Even though most of the information required for their correct folding is contained in their primary sequences, we are as yet unable to accurately predict both the folding pathways and active tertiary structures of RNA species. Ribozymes are interesting molecules to study when addressing these questions because any modifications in their structures are often reflected in their catalytic properties. The recent progress in the study of the structures, the folding pathways and the modulation of the small ribozymes derived from natural, self-cleaving, RNA motifs have significantly contributed to today’s knowledge in the field.