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PubMed1977

In vitro transcription of the ribosomal RNA genes of E. coli DNA.

Bacterial ribosomal RNA synthesis was studied in an in vitro system in which the presence of heparin prevented reinitiation of transcription. The number of heparin-resistant binary complexes of RNA-polymerase and E. coli DNA depended strongly on the quality of the template. High-molecular weight DNA was a much superior template than DNA prepared by conventional techniques. Using this high-molecular weight DNA as template the amount of ribosomal RNA synthetized in one round of transcription was found to be 4-5 fold higher than the amount of rDNA present. Controls have shown that the transcription probably started at the proper initiation sites and no significant read-through form distant promoters contributed to this effect. If the binary polymerase-DNA complexes were dissociated in the presence of 0.5 M KC1 prior to transcription all RNA synthesis was strongly reduced but the proportion of rRNA increased in the transcript. However, in this case the amount of rRNA did not exceed the amount of rDNA. We propose that the promoters of the rRNA genes are complex structures, able to store 4-5 molecules of RNA polymerase and of these several polymerase only one is bound in an extremely salt-resistant form.

DNA, Bacterial↗
PubMed1977

Ribosomal protein-nucleic acid interactions. I. Isolation of a polypeptide fragment from 30S protein S8 which binds to 16S rRNA.

Within the bacterial ribosome a large number of specific protein and rRNA interactions appear to be required for assembly of the particle and its subsequent function in protein synthesis. In this communication it is shown that it is possible to isolate cyanogen bromide digestion products from ribosomal 30S protein S8 which will interact stoichiometrically with 16S rRNA. In addition to this a small binding polypeptide was generated from S8-16S rRNA complexes which were treated with proteinase K. The digestion of the complex yields a "protected" fragment of protein S8 which binds to 16S-rRNA. The isolated fragment will reassociate with 16S rRNA. It is not displaced by other 30S ribosomal proteins and blocks the binding of intact S8 to 16S rRNA. The size the possible structure of the S8 protein binding site are discussed and compared with the binding of cyanogen bromide digestion products which bind to 16S rRNA.

Amino Acids↗
PubMed1977

Interaction of ethidium bromide with ribosomes. Absorption, fluorescence, circular dichroism and sedimentation studies.

It is shown in this work that the binding of ethidium bromide to yeast ribosomes occurs through intercalation in the double-stranded rRNA regions and produces changes in the ribosomes structure, yielding unfolded subparticles, and even partial separation of proteins from rRNA at very high binding ratios. The addition of Mg2+ prevents these structural changes, probably by partial inhibition of the dye binding.

Binding Sites↗
PubMed1979

Precursor-specific nucleotide sequences can govern RNA folding.

An immediate precursor of 5S ribosomal RNA (rRNA) from Bacillus subtilis has 21 and 42 nucleotide precursor-specific segments associated with its 5' and 3' termini, respectively. On the basis of its nucleotide sequence, predicted secondary structure and location in the rRNA transcriptional unit, the 3' precursor element apparently functions during the termination of transcription. A portion of the 5' precursor element is shown to facilitate the native folding of the mature domain of the precursor. Precursor 5S rRNA molecules which lack the 5' terminal 8-9 nucleotides of the 5' precursor elements were fabricated. These abbreviated constructs assume a non-native conformation, as revealed by their behavior during polyacrylamide gel electrophoresis. The aberrant conformation is evidently forced upon the abbreviated constructs by the residual 5' precursor sequence, since its removal by the maturation endonuclease RNAase M5 precipitates the reordering of the mature domain into its native conformation. Inspection of the nucleotide sequence of the 5S precursor suggested the nature of the conformational aberration, and gel electrophoresis analyses of limited nuclease digests of end-labeled precursors in the native and aberrant conformations are consistent with the derived model. We conclude taht the 5' terminal six nucleotides in the intact 5S precursor assist in the folding of the mature domain by forming a base-paired duplex with neighboring nucleotides, thereby preventing that adjacent sequence from engendering the abnormal conformation. The involvement of precursor-specific sequences and conformational dynamics in RNA function are discussed.

Bacillus subtilis↗
PubMed1979

Selective suppression of the transcription of ribosomal genes in mouse-human hybrid cells.

Mouse-human hybrid cells that preferentially segregate either mouse or human chromosomes were analyzed for their relative content of mouse and human rRNA genes and for their capacity to transcribe these genes. A distinctive Hind III restriction fragment containing 28S rRNA sequences was used to distinguish between mouse and human rDNA and a set of distinctive loop structures in the 45S pre-rRNA was used to distinguish between mouse and human gene transcripts. Our results indicate that the genes of only one species are transcriptionally active in these hybrid cells, even though both sets of genes are present.

Animals↗
PubMed1979

Fine structure of ribosomal RNA. II. Distribution of methylated sequences within Xenopus laevis rRNA.

The distribution of methyl groups in rRNA from Xenopus laevis was analyzed by hybridization of rRNA to subfragments of either of two cloned rDNA fragments, X1r11 and X1r12, which together constitute a complete rDNA repeat unit. Using a mixture of 3H-methyl plus 32P-labelled rRNA as probe, the molar yield of methyl groups per rRNA region in hybrid could be calculated. For this calculation the length of the rRNA coding region in each DNA subfragment is needed, which was determined for X1r11 subfragments by the nuclease S1 mapping method of Berk and Sharp. The results show that both in 18S and 28S rRNA the methyl groups are nonrandomly distributed. For 18S rRNA, clustering was found within a 3' terminal fragment of 310 nucleotides. For 28S rRNA, clustering of methyl groups was found within a region of 750 nucleotides in length, which ends 500 nucleotides from the 3' end. In contrast, the 28S rRNA 5' terminal region of 900 nucleotides is clearly undermethylated. The general position of methyl groups in 28S rRNA correlates with the location of evolutionarily conserved sequences in this molecule, as recently determined in our laboratory.

Animals↗
PubMed1979

The organization of the ribosomal RNA genes of Chironomus tentans and some closely related species.

Southern gel analysis of total DNA from Chironomus tentans showed that the rRNA genes (rDNA) are homogeneous in structure. After cloning in Escherichia coli plasmid pBR313, the rDNA organisation was further studied by restriction fragment analysis and R-loop mapping. No heterogeneity could be detected by heteroduplex analysis of six different cloned rRNA cistrons. R-loop sizes of 1.69 and 3.63 kilobases (kb) were measured for the 18S and 28S rRNA coding sequences. The two spacers are 0.75 and 1.77 kb long. Southern gel analysis showed also a homogeneous rDNA structure for a Canadian population of C. tentans and C. pallidivittatus. The same technique indicated, however, that the rDNA of two other closely related species of C. thummi and C. melanotus is heterogeneous in structure. A possible correlation between this heterogeneity and the presence of heterochromatin in these species is discussed.

Animals↗
PubMed2026

[Exploring the mechanism underlying the efficacy differences of "Tiaojing Cuyun Acupuncture"for premature ovarian failure based on vaginal microbiota structure].

OBJECTIVE: To observe the efficacy of "Tiaojing Cuyun Acupuncture" combined with hormone replacement therapy in the treatment of premature ovarian failure (POF), and to investigate differences in vaginal microbiota among patients with different therapeutic responses, thereby preliminarily exploring the mechanism underlying efficacy differences. METHODS: Ninety-eight patients with POF were randomly divided into an observation group (49 cases, 1 case was eliminated)and a control group (49 cases, 1 case dropped out). The control group was treated with hormone replacement therapy with Femoston, one tablet each time, once daily. On the basis of the control group, the observation group was additionally treated with "Tiaojing Cuyun Acupuncture". Acupoint group 1 included Baihui (GV20), Zhongwan (CV12), Guanyuan (CV4), and bilateral Tianshu (ST25), Zigong (EX-CA1), Dahe (KI12), Zusanli (ST36), Sanyinjiao (SP6), and Taichong (LR3). Acupoint group 2 included Baihui (GV20), bilateral Shenshu (BL23), Ciliao (BL32), and Taixi (KI3). The two acupoint groups were used alternately, beginning with acupoint group 1. Treatment was administered once every other day, three times per week.Both groups were treated for three menstrual cycles. Serum follicle-stimulating hormone (FSH), luteinizing hormone (LH),estradiol (E2), and anti-M &#xfc; llerian hormone (AMH) levels on days 3-5 of the menstrual cycle were measured before and after treatment in the two groups. Self-rating anxiety scale (SAS) scores were assessed before and after treatment, and clinical efficacy was evaluated in the two groups. Five effective patients (G0 subgroup) and five ineffective patients (G1 subgroup)were randomly selected from each group, and their vaginal microbiota structure was analyzed using 16S rRNA sequencing. RESULTS: After treatment, FSH levels in both groups were lower than those before treatment (P<0.05); SAS scores in both groups were lower than those before treatment (P<0.05), and the observation group had lower SAS score than the control group (P<0.05). The total effective rate was 77.1% (37/48) in the observation group, which was higher than 56.3% (27/48) in the control group (P<0.05). Vaginal microbiota analysis showed that at the phylum level, the relative abundance of Firmicutes in the G0 subgroup of the control group was higher than that in the G1 subgroup, while the relative abundances of Bacteroidetes, Actinobacteria and Proteobacteria were lowed in the G0 subgroup. In contrast, the observation group exhibited an opposite trend: the G0 subgroup had lower Firmicutes abundance but higher abundances of Actinobacteria, Bacteroidetes and Proteobacteria compared with the G1 subgroup. At the family and genus levels, Bifidobacterium was enriched in the G0 subgroups of both groups, whereas Lactobacillus predominated in the G1 subgroups. The G0 subgroup of the control group showed higher abundance of Gardnerella, while both Lactobacillus and Gardnerella were concurrently elevated in the G1 subgroup of the observation group. Additionally, in the observation group indicated that Clostridiales and Rikenellaceae were significantly more abundant in the G0 subgroup than in the G1 subgroup (P<0.05). CONCLUSION: The "Tiaojing Cuyun Acupuncture" combined with hormone replacement therapy is superior to hormone replacement therapy alone in improving anxiety. There are differences in vaginal microbiota structure among patients with different theraputic efficacy, suggesting that the vaginal microecological environment may be involved in the mechanism of treatment response in POF.

Humans↗
PubMed1979

Alteration in thermal stability of ribosomes from Drosophila melanogaster with age.

Thermal analysis of high salt (0.5 M) washed ribosomal monomers from young and old male Drosophila melanogaster revealed an 8 degrees C downshift in the mean temperature of denaturation (Tm). Moreover, there was observed a marked loss in the ability of ribosomes extracted from older flies to reassociate upon cooling. These observations suggest that age-dependent alterations in the structural integrity of the rRNA-r protein complex could, at least in part, be responsible for the diminished capacity for protein synthesis in this species with advancing age.

Aging↗
PubMed1979

Properties of Escherichia coli 16S ribosomal ribonucleic acid treated with 4,5',8-trimethylpsoralen and light.

16S rRNA reacted with the furocoumarin 4,5',8-trimethylpsoralen (trioxsalen) and 360-nm light showed a number of chemical and physical differences from untreated RNA. After extensive irradiation, five molecules of trioxsalen were bound per molecule of RNA. The trioxsalen-treated RNA had an altered ultraviolet absorption spectrum and a distinctive fluorescence emission spectrum. The modified RNA was significantly more resistant to T1 ribonuclease digestion than was control RNA. Treated RNA, when mixed with purified ribosomal proteins, was not functional in the in vitro reconstitution of 30S subunits and yielded more slowly sedimenting particles which were inactive in protein synthesis assays. By contrast, 16S rRNA within the 30S subunit structure did not exhibit these changes when reacted with the same dose of trioxsalen and light, suggesting that the ribosomal proteins were effective in protecting the RNA from interaction with the drug.

Cell Fractionation↗
PubMed2026

Concurrent ecological and evolutionary processes contribute to mutualism breakdown between legumes and rhizobia.

Though they jointly shape community responses to environmental perturbations, ecology and evolution are often examined separately, even in microorganisms where both occur over short timescales. Here we examine ecological and evolutionary responses to 33&#xa0;years of nitrogen fertilization using the legume-rhizobium mutualism. Pairing a manipulative inoculation study with full-length 16S rRNA gene amplicon sequencing and structural equation modeling allows us to synthesize across biological scales: whole bacterial community, genus Rhizobium, Rhizobium ASVs, and symbiosis plasmids. Clover's preferred partner decreases in N-addition soils, limiting host growth, while a diverse and largely uncharacterized Rhizobium community increases. This ecological change is compounded by a concurrent evolutionary degradation of symbiont partner quality via changing frequencies of symbiotic plasmids. Ecological (rarer symbionts) and evolutionary (inferior symbionts) processes each accounted for roughly half of this loss of host benefit, revealing that ecology and evolution jointly shape mutualism breakdown over the short timescales typical of microbial systems.

ecology↗
PubMed1979

Analysis of RNA secondary structure by photochemical reversal of psoralen crosslinks.

Aminomethyltrioxsalen (AMT), a psoralen, is known to cause interstrand crosslinks in double stranded nucleic acids. We have demonstrated the photochemical reversal of this reaction, and have used this result to develop a method for identification of specific sequences which are adjacent because of RNA secondary structure formation. E. coli 5S rRNA is used as a model system. We isolated and characterized a product that is derived from the stem region of 5S RNA.

Base Composition↗
PubMed2026

Probiotic Lacticaseibacillus casei 2S-1 Attenuates Escherichia coli-Induced Enteritis via Gut Microbiota Modulation and Host Gene Regulation.

Maintaining gut microbial homeostasis is crucial for host health, whereas infection with Escherichia coli (E. coli) is a major contributor to intestinal inflammation and microbial dysbiosis. Recent research has focused on probiotic strategies for managing enteric inflammatory disorders. Previous studies have shown that beneficial microorganisms show protection through modulating host immune responses, enhancing intestinal epithelial barrier integrity, and inhibiting pathogenic bacteria. To evaluate the prophylactic effectiveness of a recently isolated strain, Lacticaseibacillus casei 2S-1, in a murine model of E. coli-induced enteritis, this study focuses on interactions within the microbiota-intestinal-immune axis, together with host transcriptional responses and pathway enrichment associated with oxidative stress and mitochondrial function. In vitro analysis of probiotic features, including growth dynamics, acidogenic capacity, and tolerance to acidic and bile salt environments, as well as genetic safety profiling, followed the methodical isolation and taxonomic identification of L. casei 2S-1. A preventive intervention protocol was established, and a murine model of enteritis was induced by exposure to E. coli. Histopathological analyses were performed to observe in vivo safety and protective efficacy. Changes in gut microbial structure were characterized by 16S rRNA gene sequencing, while host responses were identified by intestinal immunohistochemistry and transcriptome profiling. L. casei 2S-1 showed probiotic properties. In vitro analyses showed that the strain exhibited tolerance to acidic and bile salt conditions, and its untreated culture supernatant showed antimicrobial activity against pathogenic bacteria. Its safety profile was supported by genomic analysis, which verified the lack of virulence-associated genes and antibiotic resistance factors. In vivo, L. casei 2S-1 pretreatment reduced mortality and intestinal inflammation, modulated gut microbial composition, and preserved intestinal barrier-associated protein expression in infected mice. This study provides experimental evidence supporting the prophylactic effects of L. casei 2S-1 and its associations with gut microbiota modulation and host transcriptional responses, providing a foundation for further investigation of probiotic-based preventive strategies against intestinal infections.

Animals↗
PubMed1979

Intermolecular base-paired interaction between complementary sequences present near the 3' ends of 5S rRNA and 18S (16S) rRNA might be involved in the reversible association of ribosomal subunits.

Highly conserved sequences present at an identical position near the 3' ends of eukaryotic and prokaryotic 5S rRNAs are complementary to the 5' strand of the m2(6)A hairpin structure near the 3' ends of 18S rRNA and 16S rRNA, respectively. The extent of base-pairing and the calculated stabilities of the hybrids that can be constructed between 5S rRNAs and the small ribosomal subunit RNAs are greater than most, if not all, RNA-RNA interactions that have been implicated in protein synthesis. The existence of complementary sequences in 5S rRNA and small ribosomal subunit RNA, along with the previous observation that there is very efficient and selective hybridization in vitro between 5S and 18S rRNA, suggests that base-pairing between 5S rRNA in the large ribosomal subunit and 18S (16S) rRNA in the small ribosomal subunit might be involved in the reversible association of ribosomal subunits. Structural and functional evidence supporting this hypothesis is discussed.

Base Sequence↗
PubMed1979

Localization of transcribed regions on extrachromosomal ribosomal RNA genes of Tetrahymena thermophila by R-loop mapping.

R-loop hybridization and electron microscopy were used to map the RNA transcription products of the extrachromosomal rRNA genes of Tetrahymena thermophila. The mature 17S and 26S rRNAs and the nuclear 35S pre-rRNA and pre-26S rRNA were located with a precision of approximately 100 base pairs. A 370-base pair intervening sequence was found in the 26S coding region. It has the same size and relative location as that found in Tetrahymena pigmentosa [Wild, M.A. & Gall, J.G. (1979) Cell 16, 565-573]. One class of R-loop structures formed by nuclear pre-rRNA provided preliminary evidence for a primary transcript that contains the intervening sequence. The results suggested a processing scheme in which splicing of the intervening sequences is followed by a series of strand cleavages to give the mature 17S and 26S rRNAs. Analysis of the data also showed that RNA . DNA and DNA . DNA duplexes, when mounted for electron microscopy by the R-loop procedure, have the same length per base pair within 4%.

Animals↗
PubMed1978

Evidence on the conformation of HeLa-cell 5.8S ribosomal ribonucleic acid from the reaction of specific cytidine residues with sodium bisulphite.

The reaction of HeLa-cell 5.8S rRNA with NaHSO3 under conditions in which exposed cytidine residues are deaminated to uridine was studied. It was possible to estimate the reactivities of most of the 46 cytidine residues in the nucleotide sequence by comparing 'fingerprints' of the bisulphite-treated RNA with those of untreated RNA. The findings were consistent with the main features of the secondary-structure model for mammalian 5.85S rRNA proposed by Nazar, Sitz, & Busch [J. Biol. Chem (1975) 250, 8591--8597]. Five out of six regions that are depicted in the model as single-stranded loops contain cytidine residues that are reactive towards bisulphite at 25 degrees C (the other loop contains no cytidine). The cytidine residue nearest to the 3'-terminus is also reactive. Several cytidines residues that are internally located within proposed double-helical regions show little or no reactivity towards bisulphite, but the cytidine residues of several C.G pairs at the ends of helical regions show some reactivity, and one of the proposed loops appears to contain six nucleotides, rather than the minimum of four suggested by the primary structure. Two cytidine residues that are thought to be 'looped out' by small helix imperfections also show some reactivity.

Base Sequence↗
PubMed1978

Complementary sequences 1700 nucleotides apart form a ribonuclease III cleavage site in Escherichia coli ribosomal precursor RNA.

The nucleotide sequence of Escherichia coli DNA at both ends of the gene for 16S rRNA has been determined for two rRNA operons, rrnD and rrnX. The 400 nucleotides we have examined exhibit only one base change between rrnD and rrnX. Within the 160 nucleotides that precede mature 16S rRNA sequences are cleavage sites for several E. coli endonucleases, including RNase III. A 240-nucleotide segment encompassing the 16S 3' end contains another RNase III site and the point of presumed RNase P scission at the 5' end of tRNA1Ile, the first tRNA appearing in the 16-23S spacer region of rrnD and rrnX. Most importantly, the DNA sequences predict that regions flanking the 16S gene in the rRNA primary transcript extensively base pair to form a double-helical structure whose hairpin loop includes the entire mature 16S molecule; within this structure is a 26-base-pair stem containing the two sequences at which RNase III action generates the 5' and 3' ends of a previously characterized precursor to 16S rRNA. Although our proposed secondary structure for this RNase III site is superficially dissimilar to previously described cleavage sites in the T7 early mRNA precursor, certain common features may constitute signals for RNase III recognition. The suggestion that distant portions of an RNA molecule can form a secondary structure within which specific endonucleolytic cleavages occur may have mechanistic implications for the joining of noncontiguous portions of gene sequences evident in several eukaryotic mRNAs.

Base Sequence↗