Quantitative Bestimmung von RNS-Fraktionen im Gehirn frisch geschlüpfter Bienen (Apis mellifica)

Summary In the brain of the honeybee (Apis mellifica), it was found that the rRNA content decreases rapidly during the first 2 days of adult life. An increase is observed from days 3 to 5, followed by another decrease to a level inferior to that of day 2 to 3. Except for a rise on the 5th day, 4s RNA remains constant. An unidentified RNA fraction of low molecular weight (D) sharply decreases on day 5. The possibility is discussed that these results reflect changes in RNA metabolism that can be related to the sequences of activity observed in the bees during the first 9 days after hatching.     

Amount of ribosomal DNA and seed protein content in the genusTriticum

Summary rRNA/DNA hybridization experiments were performed and seed protein content was determined in several lines of 4 species ofTriticum (wheat). No correlation between rRNA gene number and seed protein content was found.Supported by CNR contract No. 74/0267.     

Divergence towards a dead end? Cleavage of the divergent domains of ribosomal RNA in apoptosis

In several cases of apoptotic death the large ribosomal subunit 28S rRNA is specifically cleaved. The cleavages appear at specific sites within those domains of the rRNA molecule that have shown exceptional high divergence in evolution (D domains). The cleavages accompany rather than precede apoptosis, and there is a positive, but not complete, correlation between rRNA cleavage and internucleosomal DNa fragmentation. Most cell types studied so far show two alternative cleavage pathways that are mutually exclusive. Cleavage can either start in the D8 domain with secondary cuts within a subdomain of D2 (D2c), or in the D2 domain with subsequent excision of the D2c subdomain. The latter pathway is of particular interest since D2 (unlike D8) is normally inaccessible for RNase attack. That apoptosis specifically affects the ribosomal divergent domains suggests that these domains, which make up roughly 25% of total cellular RNA, might have evolved to serve functions related to apoptosis. Future studies will be directed to test the hypothesis that rRNA fragmentation may be part of an apoptotic program directed against the elimination of illegitimate (viral?) polynucleotides.     

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.     

RNA biosynthesis in isolated prothoracic glands ofTenebrio molitor in vitro

Summary The prothoracic Glands ofTenebrio molitor synthesize in vitro mainly rRNA. The rate of RNA synthesis reaches a maximum at day 10 of the last larval instar, which coincides with the event of apolysis.The work was supported by the Deutsche Forschungsgemeinschaft. We thank Dr.H. Winter, Heidelberg, for helpful suggestions for the RNA separations.     

The effect of cycloheximide on nuclear uH2A content

The effect of intraperitonal cycloheximide administration on acid-soluble rat liver chromatin proteins has been investigated by electrophoresis in acetic acid-urea polyacrylamide gels. A nonhistone protein, which migrates between oxidized histone H3 and histone H1 has been found to be increased in amount following cycloheximide treatment. This protein seems to be identical with semihistone protein H24 (uH2A). A possible relationship of uH2A to the inhibition of rRNA synthesis is discussed.     

The effect of cycloheximide on nuclear uH2A content

Summary The effect of intraperitonal cycloheximide administration on acid-soluble rat liver chromatin proteins has been investigated by electrophoresis in acetic acid-urea polyacrylamide gels. A nonhistone protein, which migrates between oxidized histone H3 and histone H1 has been found tobe increased in amount following cycloheximide treatment. This protein seems to be identical with semihistone protein H24 (uH2A). A possible relationship of uH2A to the inhibition of rRNA synthesis is discussed.This work was supported by the Turkish Scientific and Technical Research Council (TUBITAK) Project No. TAG 339     

In situ hybridization of rDNA on chromosomes of the honeybee,Apis mellifera L.

DNA probes containing the repeated rDNA region ofDrosophila melanogaster (coding for e.g. 28S and 18S rRNA) hybridized in situ to distinct regions of two heterologous mitotic chromosomes of the honeybee, identifying the nucleolus organizing regions (NORs). The method allows a rapid establishment of a physical map ofApis mellifera using other DNA probes ofDrosophila. This is the first report on well-defined chromosomal markers in the honeybee.     

Partial sequence of the gene for a serine protease from a halophilic archaeumhaloferax mediterranei R4, and nucleotide sequences of 16S rRNA encoding genes from several halophilic archaea

A part of the gene coding for a halophilic serine protease from a halophilic archaeumHaloferax mediterranei R4 was amplified by PCR and its 672 nucleotide sequence was determined. Tentative translation to the amino acid sequence suggested that the enzyme was quite similar to halolysin produced by another halophilic archaeum strain 172P1. Nucleotide sequences of 16S rRNA encoding genes from 9 halophilic archaea were determined. Alignment of 19 sequences known so far showed that there are more than 20 positions carrying bases or deletions specific for each halobacterial genus:Halobacterium, Haloarcula, Haloferax, andHalococcus.     

Plant ribosome-inactivating proteins type II induce the unfolded protein response in human cancer cells

Cytotoxic ribosome-inactivating proteins (RIPs) of type II such as ricin were investigated as anti-cancer agents, but also pose a threat as biological weapons. The molecular mechanism leading to their toxic effects is, however, not yet clear. The current paradigm, which states that the irreversible depurination of 28S rRNA results in a general translational arrest eventually leading to cell death, has been questioned. Using micro-array, qRT-PCR and Western blot, we identified the unfolded protein response (UPR), a cellular mechanism activated in response to endoplasmic reticulum stress, that is induced in HCT116 and MDA-MB-231 cells exposed to the plant type II RIPs ricin, riproximin and volkensin. Apoptosis was induced by concentrations at which translation of UPR-related genes still occurred, despite concomitant ribosomal depurination. We conclude that UPR induction represents a model that better describes the cellular effects of RIP exposure at concentrations at which selected proteins are translated despite ribosomal depurination.     

The multi-KH protein vigilin associates with free and membrane-bound ribosomes

The-multi-KH domain protein vigilin has been identified by ex vivo experiments as both a tRNA- and/or mRNA-binding protein. We show here that in vitro under conditions previously shown to allow tRNA binding, recombinant vigilin also binds to selected mRNA species and ribosomal RNA. An in vivo link of vigilin to mRNA and rRNA was elucidated by several approaches. (i) Coexpression/costimulation of vigilin was found with many other proteins independently of whether their mRNA was translated on free or membrane-bound ribosomes. (ii) A close codistribution of vigilin with free ribosomes was seen in the cytoplasm while nucleoli were a major organelle of vigilin accumulation in the nucleus. (iii) Furthermore, free and membrane-bound ribosomes can be enriched for vigilin which suggests that this binding does not depend on the class of mRNA translated. Therefore, we suggest that vigilin does not distinguish between free or membrane-bound ribosomes but is generally necessary for the localization of mRNAs to actively translating ribosomes.Received 20 June 2003; received after revision 25 July 2003; accepted 29 July 2003     

Ribosome-inactivating proteins: progress and problems

Ribosome-inactivating proteins (RIPs), mostly from plants, are enzymes which depurinate rRNA, thus inhibiting protein synthesis. They also depurinate other polynucleotide substrates. The biological activity of RIPs is not completely clarified, and sometimes independent of the inhibition of protein synthesis. There are differences in the cytotoxicity of RIPs and, consequently, in their toxicity to animals. Some RIPs are potent toxins, the best known being ricin, a potential biological weapon. New toxins have recently been identified. RIPs cause apoptotic and necrotic lesions, and induce production of cytokines causing inflammation. RIPs are potentially useful in agriculture and medicine because (i) they have antiviral activity and (ii) they are used for the preparation of conjugates with antibodies (‘immunotoxins’) or other carriers, rendering them specifically toxic to the cell target of the carrier, which may be helpful in therapy. The distribution, mechanism of action and role in nature of RIPs are not completely understood, and we can expect several future developments in their practical application. Received 17 February 2006; received after revision 23 March 2006; accepted 2 May 2006     

Evidence that miRNAs are different from other RNAs

An examination of 513 known pre-miRNAs and 237 other RNAs (tRNA, rRNA, and mRNA) revealed that miRNAs were significantly different from other RNAs (p < 0.001). miRNA genes were less conserved than other RNA genes, although their mature miRNA sequences were highly conserved. The A+U content of pre-miRNAs was higher than non-coding RNA (p < 0.001), but lower than mRNAs. The nucleotides in pre-miRNAs formed more hydrogen bonds and base pairs than in other RNAs. miRNAs had higher negative adjusted minimal folding free energies than other RNAs except tRNAs (p < 0.001). The MFE index (MFEI) was a sufficient criterion to distinguish miRNAs from all coding and non-coding RNAs (p < 0.001). The MFEI for miRNAs was 0.97, significantly higher than tRNAs (0.64), rRNAs (0.59), or mRNAs (0.65). Our findings should facilitate the prediction and identification of new miRNAs using computational and experimental strategies. Received 5 October 2005; received after revision 4 November 2005; accepted 16 November 2005     

Changes to cellular water and element content induced by nucleolar stress: investigation by a cryo-correlative nano-imaging approach

The cell is a crowded volume, with estimated mean mass percentage of macromolecules and of water ranging from 7.5 to 45 and 55 to 92.5 %, respectively. However, the concentrations of macromolecules and water at the nanoscale within the various cell compartments are unknown. We recently developed a new approach, correlative cryo-analytical scanning transmission electron microscopy, for mapping the quantity of water within compartments previously shown to display GFP-tagged protein fluorescence on the same ultrathin cryosection. Using energy-dispersive X-ray spectrometry (EDXS), we then identified various elements (C, N, O, P, S, K, Cl, Mg) in these compartments and quantified them in mmol/l. Here, we used this new approach to quantify water and elements in the cytosol, mitochondria, condensed chromatin, nucleoplasm, and nucleolar components of control and stressed cancerous cells. The water content of the control cells was between 60 and 83 % (in the mitochondria and nucleolar fibrillar centers, respectively). Potassium was present at concentrations of 128–462 mmol/l in nucleolar fibrillar centers and condensed chromatin, respectively. The induction of nucleolar stress by treatment with a low dose of actinomycin-D to inhibit rRNA synthesis resulted in both an increase in water content and a decrease in the elements content in all cell compartments. We generated a nanoscale map of water and elements within the cell compartments, providing insight into their changes induced by nucleolar stress.     

Seasonal variations in the nyctohemeral rhythm of plasma testosterone in the European badger Meles meles L

In the badger a seasonal sexual rhythm of the plasma testosterone is observed. There is also a nycthemeral rhythm of the testosterone secretion; during the regressed period of the testis this rhythm is bimodal with testosterone peaks during the light phase of the day; during the active period and "activity rhythm" with many transitorys peaks during the dark phase is added.     

Seasonal plasma testosterone variations in the stone marten]

Plasma testosterone levels change with annual sexual cycle of the stone marten. Very low during the decrease and the quiescence of the testis, it rises during the testis onset and reaches a maximal peak during the co?t period (May to July).