Showing papers on "Ribosomal DNA published in 1978"
TL;DR: Experiments with T4 DNA polymerase suggested that there are no free cohesive ends on the rDNA of the kind found in bacteriophage λ DNA, and the orientation of the strands carrying the repeating hexanucleotide sequence was determined, and a model for the termini of the r DNA is presented.
958 citations
TL;DR: Restriction enzymes Hpa II, Ava I, Hha I and Hae II have been found to distinguish Xenopus laevis somatic rDNA † from amplified rDNA, and the pattern of methylation in erythrocyte rDNA is studied.
410 citations
TL;DR: Complex repeating restriction multimers and a simple AT rich satellite isolated with Hoechst 33258 were localized by in situ hybridization to human chromosomes and labelled predominantly the long arms of the Y chromosome.
Abstract: Complex repeating restriction multimers and a simple AT rich satellite isolated with Hoechst 33258 ( less than or equal to 0.5% of the human genome) were localized by in situ hybridization to human chromosomes. The complex repeats were clustered at the centromeres, consonant with their integration in tandem arrays at these loci; these sequences were very prominent on chromosomes 7, 10 and 19, sites not previously identified with any specific human repeated sequence. The Hoechst simple satellite labelled predominantly the long arms of the Y chromosome. Although this simple satellite and the complex restriction multimers did not hybridize with each other, and did not contain detectable ribosomal sequences, both isolates additionally labelled the nucleolus organizing regions (NORs) of acrocentric chromosomes.--The possible relationship of complex and simple repeated DNAs, and their assignment to specific chromosomal domains, is discussed.
219 citations
TL;DR: A surprising result is the interruption of all chloroplast 23S rRNA genes by a 940 base pair (bp) intervening sequence at a site 0.27 ± 0.04 kb distant from the 5′ end of the 23S RNA coding strand.
171 citations
TL;DR: The R-loop method was improved with respect to the length calibration of RNA/DNA duplexes and to the spreading conditions resulting in fully extended 18 S and 25 S rRNA R-loops.
152 citations
TL;DR: The results show that this gene may be transcribed with remarkable fidelity in injected oocytes, and that untranscribed genes are converted into a characteristic chromatin structure.
Abstract: DNA CLONING and the direct visualisation of chromatin transcription by electron microscopy provide useful details of the structure and function of genes, but the value of these techniques would be even greater if they could be applied to the same genes or segments of DNA. Our previous work1 on amplified ribosomal DNA (rDNA) of the water beetle Dytiscus showed that rDNA injected into oocytes is correctly transcribed. Gradients of growing rRNA fibrils could be unambiguously recognised as correct transcription when compared to the characteristic transcription pattern observed in the original cell type. We have now extended the usefulness of this technique to recombinant DNA, choosing as an example of a cloned vertebrate gene a single rDNA repeat of Xenopus laevis contained in plasmid DNA. The results show that this gene may be transcribed with remarkable fidelity in injected oocytes, and that untranscribed genes are converted into a characteristic chromatin structure.
113 citations
TL;DR: The homology between the nontranscribed spacers in X and Y rDNA was studied with cloned fragments and stable heteroduplexes were found which showed that these regions on the two chromosomes are very similar.
113 citations
TL;DR: A heteroduplex analysis of the clones obtained with a three-component Hin dIII vector showed that the center part of the λ genome carrying λ recombination and regulation genes (57 to 77% λ) can become inverted without apparent decrease of growth capacities.
108 citations
TL;DR: Fragments of rDNA‡ from Drosophila melanogaster produced by the restriction endonuclease Eco RI were cloned in the form of recombinant plasmids in Escheriehia coli and one unusual rDNA fragment was isolated as a recombinant molecule.
107 citations
TL;DR: The intragenic organization of ribosomal DNA from a diploid strain of Saccharomyces cerevisiae was analyzed by using recombinant DNA molecules constructed in vitro and indicated that the yeast ribosome genes are homogeneous and extensively clustered.
Abstract: The intragenic organization of ribosomal DNA from a diploid strain of Saccharomyces cerevisiae was analyzed by using recombinant DNA molecules constructed in vitro. Restriction analysis of the yeast ribosomal DNA with the EcoRI restriction enzyme indicated that eight restriction fragments were present in the ribosomal DNA of this strain: X9 (1.87 X 10(6) daltons), A (1.77 X 10(6) daltons), B (1.48 X 10(6) daltons), C (1.22 X 10(6) daltons), D (0.39 X 10(6) daltons), E (0.36 X 10(6) daltons), F (0.22 X 10(6) daltons), and G (0.17 X 10(6) daltons). These fragments were distributed between two different types of ribosomal DNA genes, which had the restriction maps: (formula: see text) in which the underlined region shows the repeating unit. The diploid yeast strain contained approximately equal amounts of each of these two types of genes. The analysis of the recombinant DNA molecules also indicated that the yeast ribosomal genes are homogeneous and extensively clustered. Images
94 citations
TL;DR: Analysis of the mobility of total cell DNA in 0.15% agarose gels indicates that the majority of the rDNA is not covalently attached to chromosomal DNA.
Abstract: Restriction enzyme mapping of snap-back DNA has been used to show that the ribosomal DNA (rRNA genes and spacers) from Dictyostelium discoideum exists as 88 kb (kb=1,000 base pairs) linear palindromic dimers. Analysis of the mobility of total cell DNA in 0.15% agarose gels indicates that the majority of the rDNA is not covalently attached to chromosomal DNA.
TL;DR: Chloroplast ribosomal DNA from Euglena gracilis was partially purified, digested with restriction endonucleases Bam HI or Eco RI and cloned into bacterial plasmids, which permitted the localization on a Bam HI map of the chloroplast DNA three tandemly arranged chlorobase pair spacer region genes.
TL;DR: The presence of ribosomal cistrons in an altered nucleosome configuration may be related to changes in functional states of rDNA chromatin.
Abstract: The localization of DNA sequences coding for ribosomal RNA was studied by hybridization of purified ribosomal RNA to DNA from chromatin fragments prepared by limited digestion of Physarum nuclei with staphylococcal nuclease. The 32P-labeled 19S and 26S RNA hybridized to DNA from nucleosome monomers, dimers, trimers, and higher oligomers, separated by sucrose gradient centrifugation, although the level of hybridization to DNA from nucleosome fractions was less than the level of hybridization to undigested nuclear DNA. The distribution of 19S and 26S rDNA sequences in the nucleosome fractions differed from the distribution of bulk DNA in that the rDNA sequences were recovered primarily in two fractions containing monomer-sized DNA lengths (140-160 base pairs). The percentage of DNA hybridizing to 19S plus 26S RNA was greater in peak A, the more slowly sedimenting monomer peak, than in any other chromatin fraction at all stages of digestion. Peak A and monomer particles differed in protein content and distribution. The presence of ribosomal cistrons in an altered nucleosome configuration may be related to changes in functional states of rDNA chromatin.
TL;DR: The relative positions of endo R .
Abstract: 1
The relative positions of endo R. EcoRI and endo R. BglII cleavage sites are mapped within the linked DNA fragments Bam-E-E-D of the Euglena gracilis chloroplast DNA.
2
The DNA segment Bam-E-E-D contains three contiguous repeated segments of approximately 5600 base pairs.
3
Each repeated segment can code for an rRNA gene (16-S and 23-S).
TL;DR: A palindrome structure for the ribosome nucleoprotein molecules is demonstrated by electron microscopy of actively transcribing ribosomal RNA genes, and polarity of transcription matrices imply that 19S rRNA is transcribed prior to 26S r RNA.
Abstract: Nucleoli were purified from the slime mold Physarum polycephalum and assayed for enrichment in ribosomal DNA by analytical ultracentrifugation. Greater than 90% of the DNA from nucleoli comprises a satellite band characteristic of Physarum ribosomal DNA (rDNA) in a CsCl equilibrium sedimentation gradient. Over 75% of the nucleolar DNA molecules are 37×106 Daltons, a further characteristic of Physarum rDNA. Nucleoli incubated with micrococcal nuclease yield a distribution of discrete DNA fragments indicative of nucleosome subunits; these digestion products are indistinguishable in size from those of total nuclear chromatin. The nucleosome DNA repeat length varied with increasing digestion from 175 down to 150 base pairs. A palindrome structure for the ribosomal nucleoprotein molecules is demonstrated by electron microscopy of actively transcribing ribosomal RNA genes, which required modification of usual methods for dispersing chromatin. In the center of each palindrome is a 6.0–6.5 μm non-transcribed “spacer” region which exhibits a beaded nucleosome structure. Transcription initiates at points on either side of the central spacer, as evidenced by 4.0–4.2 μm matrices of growing rRNA fibrils extending to each end of the palindrome. The polarity of transcription matrices, together with information about the sites of rRNA coding sequences, imply that 19S rRNA is transcribed prior to 26S rRNA.
TL;DR: Sequences in the cloned Drosophila melanogaster rDNA fragments described by Dawid et al. (1978) were compared by heteroduplex mapping and deletion loops were observed at variable positions in the spacer region suggesting that spacers are internally repetitious.
TL;DR: The 5S ribosomal RNA genes have been localized in mitotic and lampbrush chromosomes of Triturus vulgaris meridionalis by in situ hybridization as mentioned in this paper.
Abstract: The 5S ribosomal RNA genes have been localized in mitotic and lampbrush chromosomes of Triturus vulgaris meridionalis by in situ hybridization These genes are clustered in a single locus in an intercalary position of the long arm of chromosome XI In lampbrush chromosome XI the 5S genes are located near a loop landmark mapped at 66 units
TL;DR: Evidence is cited indicating that, at least in man, sites containing satellite DNA, which do not contain rDNA, are routinely found in association with the nucleolus, and it is suggested that this association may indicate a functional relationship between rDNA and HHR-DNA in man and the hominoid apes.
Abstract: The distributions of ribosomal (18s + 28s) DNA in the orangutan (Pongo pygmaeus) and lowland gorilla (Gorilla gorilla gorilla) have been investigated by hybridization in situ, and the results compared with the distribution of this DNA in man, the chimpanzee (Pan troglodytes), and the mountain gorilla (Gorilla g. beringei) and with the distribution of sequences homologous to human satellite DNAs in these species. In the orangutan all sites of ribosomal DNA also contain human-homologous repeated DNA (HHR-DNA), and only the Y chromosome contains HHR-DNA but no ribosomal DNA (rDNA). In man and the chimpanzee, all sites of rDNA also contain HHR-DNA, but there are autosomal sites containing HHR-DNA that do not contain rDNA. In the lowland gorilla, only two pairs of chromosomes contain rDNA, and one of these contains HHR-DNA. The distribution of rDNA in all these species can be derived from that in the orangutan by postulating the loss of rDNA following Robertsonian translocation, pericentric inversion, or terminal deletion. Evidence is cited indicating that, at least in man, sites containing satellite DNA, which do not contain rDNA, are routinely found in association with the nucleolus, and it is suggested that this association may indicate a functional relationship between rDNA and HHR-DNA in man and the hominoid apes.
TL;DR: The genes coding for 17S and 25S rRNA in Paramecium tetraurealia were isolated and it was revealed that the rDNA is arranged as tandem repeats with an average repeat size of 5.5 X 10(6) daltons.
Abstract: The genes coding for 17S and 25S rRNA in Paramecium tetraurealia were isolated. The macronuclear ribosomal DNA (rDNA) exists as relatively small, extrachromosomal molecules with both linear and circular forms. Electron microscopy and restriction endonuclease analysis revealed that the rDNA is arranged as tandem repeats with an average repeat size of 5.5 X 10(6) daltons. Some heterogeneity of repeat lengths was found both by electron microscopy and by restriction enzyme analysis. The rDNA does not snap back after denaturation. This study provides additional evidence that extrachromosomal rDNA may be a common feature among lower eukaryotes. However, in contrast to several other cases, the rDNA of Paramecium is not palindromic, but occurs as tandem repeats as in higher eukaryotes.
TL;DR: A restriction enzyme analysis of human ribosomal DNA structure on total placental DNA using the Southern (1975) method revealed that a region of the non-transcribed spacer near the 3′ end of the 28 S gene was heterogeneous in size.
TL;DR: The results suggest that the transcriptionally active ribosomal genes of oocytes are partially, or perhaps transiently, associated with histones in the form of nuclease releasable nucleosomes but that the degree of this association may change with varying rates of rRNA synthesis.
Abstract: The chromatin subunit or nucleosome structure of the amplified, extrachromosomal, ribosomal genes of oocytes of the amphibian Xenopus laevis has been investigated during stages of growth when these genes are markedly changing their rates of transcriptional activity. Nucleic acid hybridization studies involving micrococcal nuclease derived monomer nucleosome DNA fragments and purified ribosomal RNAs indicate that the apparent degree of accessibility of the ribosomal genes to short-term nuclease hydrolysis varies as a function of the rate of ribosomal RNA (rRNA) transcription. However, at no stage during oocyte development are all of the amplified ribosomal genes completely accessible to nuclease hydrolysis, even in those stages with maximal rates of rRNA transcriptional activity. These results suggest that the transcriptionally active ribosomal genes of oocytes are partially, or perhaps transiently, associated with histones in the form of nuclease releasable nucleosomes but that the degree of this association may change with varying rates of rRNA synthesis. Additionally, the present data indicate that the average size of the double-stranded ribosomal DNA associated with monomer nucleosomes is the same (about 200 base pairs) in all of the oocyte stages examined regardless of the rates of rRNA synthesis in these stages.
TL;DR: The organization of the multiple genes for 18S, 5.8S and 28S rRNA in the genome of the silkworm, Bombyx mori was determined by restriction endonuclease digestion and Southern blot hybridization and the utility of this map, and particularly of the rDNA plasmids, for detailed studies of rRNA transcription and processing is discussed.
TL;DR: Deletions occur in recombinant DNA plasmids that contain yeast ribosomal DNA (rDNA) inserted into the E. coli plasmid pSC101 and pMB9 and appear to be due to the presence of a duplicated region.
TL;DR: An interesting finding was the presence of extra ribosomal DNA and satellite DNAs I, II and III in one chromosome 22 which was found in seven out of nine individuals of the family with the 13:14 translocation, and in only one of five individuals without the translocation.
Abstract: In a family with a stable dicentric 13:14 translocation chromosome, the distribution of DNA sequences complementary to satellite DNAs I, II and III and ribosomal RNA were studied. The translocation chromosome showed a loss of sequences complementary to all three satellite DNAs, located in the short arms of all the acrocentric chromosomes, but slightly more of the sequences complementary to satellite I were retained than of the other two satellite DNAs. The fact that material was lost from all three satellites indicates that they are not present as single discrete blocks in these chromosomes, when we would expect to find the distal sequences lost and the proximal ones retained, but consist of interspersed blocks with each sequence represented by more than one, and probably several blocks. There was a total loss of ribosomal DNA from the nucleolar organiser regions of the chromosomes involved in the 13:14 translocation, but an interesting finding was the presence of extra ribosomal DNA and satellite DNAs I, II and III in one chromosome 22 which was found in seven out of nine individuals of the family with the 13:14 translocation, and in only one of five individuals without the translocation. There may be a compensatory mechanism present when certain sequences are eliminated during chromosomal rearrangements. The relationship of such mechanisms to reproductive fitness is discussed.
TL;DR: It is concluded that the genes for ribosomal RNA are equally reiterated in spores, hatching amoebae and in plasmodia and they appear to be similarly organised in all stages of the life cycle examined so far.
TL;DR: The amount of DNA complementary to rRNA in viable haploid spores derived from a magnified monosomic strain is determined and several new mutations mapping on chromosome I were used to show that ribosomal DNA magnification was not due to a chromosome I duplication.
Abstract: Strains monosomic for chromosome I of Saccharomyces cerevisiae contain 25 to 35% fewer rRNA genes than do normal diploid strains. When these strains are repeatedly subcultured, colonies are isolated that have magnified their number of rRNA genes to the diploid amount while remaining monosomic for chromosome I. We have determined the amount of DNA complementary to rRNA in viable haploid spores derived from a magnified monosomic strain. Some of these haploids contained 24 to 48% more rRNA genes than a normal euploid strain. These extra genes may be responsible for the increased number of rRNA genes in the strain monosomic for chromosome I. Genetic analysis of the haploids containing extra rRNA genes suggested that these genes are linked to chromosomal DNA and are heterozygous. They were not closely linked to any centromere and were not located on chromosome I. Furthermore, all the DNA complementary to rRNA in one of these haploid strains with magnified rRNA genes sedimented at a chromosomal molecular weight, consistent with chromosomal linkage. In addition, several new mutations mapping on chromosome I were used to show that ribosomal DNA magnification was not due to a chromosome I duplication.
TL;DR: A method is described that enables a chromatin fraction containing ribosomal DNA (DNA containing sequences coding for rRNA) to be prepared from the macronuclei of growing or stationary cultures of Tetrahymena pyriformis, and it appears not to be appreciably contaminated by other DNA.
Abstract: A method is described that enables a chromatin fraction containing ribosomal DNA (DNA containing sequences coding for rRNA) to be prepared from the macronuclei of growing or stationary cultures of Tetrahymena pyriformis. This material is obtained in yields of between 25 and 75% of the theoretical maximum. The DNA in this fraction was identified as ribosomal DNA on the basis of its density and molecular weight, and it appears not to be appreciably contaminated by other DNA. The method relies on the approximate assumption that ribosomal DNA is the smallest species of DNA in chromatin in the nucleus, and avoids the use of mechanical force, or enzyme action, to fractionate chromatin.