Showing papers on "Genome published in 1975"
172 citations
TL;DR: Knowing the positions at which the five restriction enzymes cleave the genomes of the parental serotypes, it was possible to decide which regions of each recombinant DNA are composed of Ad5 and which of Ad2+ND1 sequences.
152 citations
TL;DR: The single copy sequences in the three constituent diploid genomes of hexaploid wheat appear to show near complete homology to one another.
Abstract: Reassociation kinetics of sheared hexaploid wheat DNA in 0.18 M Na+ at 60 °C show the presence of three major classes of nucleotide sequences; (1) a very rapidly reannealing fracton that comprises about 4 to 10% of the genome and reanneals virtually instantly. This fraction contains sequences which appear to be randomly distributed through at least 40% of the genome; they may be palindromic sequences; (2) a heterogeneous intermediate reannealing fraction comprising about 70–80% of the genome which consists of families with apparent repetition frequencies ranging from about 100–100000; and (3) a slow reannealing fraction. These fractions have been isolated and studied separately. Seventy percent of the slow reannealing fraction (12 to 20% of the genome) was found to contain sequences present in approximately six copies per hexaploid genome. The single copy sequences in the three constituent diploid genomes of hexaploid wheat appear to show near complete homology to one another.
141 citations
TL;DR: A blocked, methylated 5′-terminal structure—m7GpppGmpCp—in the genome RNA of avian sarcoma virus (ASV) is found.
Abstract: mRNAs of many eukaryotic cells and viruses contain blocked, methylated 5′-terminal structures of the type, m7GpppN (ref. 1). This ‘cap’ structure, and in particular the 5′-terminal 7-methylguanosine, is required for efficient translation in vitro of globin, reovirus and vesicular stomatitis virus mRNAs2,3. The genome subunits of RNA tumour viruses probably function as viral mRNA since RNA of the same base sequence is present in virus-specific polysomes of infected cells4,5 and virion genome RNA can be translated in vitro in a eukaryotic system6. Consistent with this possibility, we have found a blocked, methylated 5′-terminal structure—m7GpppGmpCp—in the genome RNA of avian sarcoma virus (ASV).
135 citations
TL;DR: The methods described should allow the molecular cloning of any portion of the E. coli genome by selection from a pool of DNA molecules containing at least several hundred different hybrids representing the entire bacterial genome.
Abstract: Using a poly(dA-dT) "connector" method, a population of annealed hybrid circular DNAs was constructed in vitro; each hybrid DNA circle containing one full-length molecule of poly(dT)-tailed DNA from E1 colicinogenic factor (Col E1) fragmented by EcoRI endonuclease annealed to any one of a collection of poly(dA)-tailed linear DNA fragments of the entire E. coli genome. This annealed, but unligated, hybrid DNA was used to transform several different auxotrophic mutants of E. coli, and by direct selection, bacterial clones were isolated which contained specific hybrid plasmids. In this manner, bacterial strains containing Col E1 hybrid plasmids carrying the entire tryptophan operon or the arabinsoe and leucine operons were isolated. The methods described should allow the molecular cloning of any portion of the E. coli genome by selection from a pool of DNA molecules containing at least several hundred different hybrids representing the entire bacterial genome.
129 citations
TL;DR: Ethidium bromide reduces the formation of superhelical viral DNA and concurrently blocks integration of the viral genome, which results in the inhibition of virus replication.
Abstract: The DNA of avian sarcoma virus assumes a closed circular configuration before integration into the host cell chromosomal DNA. Ethidium bromide reduces the formation of superhelical viral DNA and concurrently blocks integration of the viral genome. Inhibition of integration of viral DNA results in the inhibition of virus replication.
126 citations
TL;DR: A mechanism for constitutive transcriptional control is proposed by using fragments as primers for the in vitro synthesis of their neighbours to promote the synthesis of RNA from a region of the genome that is expressed very actively in vivo.
114 citations
TL;DR: The results indicate that there is little, if any, exclusively regulatory information in the reovirus genome since both in vivo and in vitro, transcripts of the ten genome segments direct the synthesis of ten polypeptides that presumably correspond to the primary gene products.
107 citations
TL;DR: Four of five Dm segments consist of sequences that are confined to single chromomeric regions in the polytene chromosomes and exhibit little or no repetition and are inconsistent with tandem repetition models of the chromomere.
106 citations
TL;DR: Kinetic analysis shows that all of the frequency components of the Drosophila genome are present in the inverted repeats, the loops P, and the flanking sequences, including middle repetitive DNA in those inverted repeat duplexes which are resistant to digestion by Mung Bean Endonuclease I.
102 citations
TL;DR: DNA infectivity studies by using the calcium phosphate and the DEAE-dextran method gave evidence that H genomes are defective: no infectious virus was recovered from permissive cells treated with heavy DNA, whereas M genome-infected cells developed cytopathic changes after 11 to 56 days.
Abstract: Two types of Herpesvirus saimiri genomes can be isolated from purified virions: (i) the M genome is a double-stranded, liniear DNA molecule with a mean contour length corresponding to 89 times 10-6 daltons. The M genome contains about 70% of unique sequences (light DNA, 36% guanine plus cytosine) and 30% reiterated sequences (heavy DNA, 71% guanine plus cytosine). (ii) the H genome is composed of heavy DNA only and is more heterogeneous in size. The sequences in the H genome are up to 40-fold reiterated, indicating defectiveness of this type of genome. The repetitions in the H genome and the M genome cross-hybridize almost completely and have identical kinetic complexity (2.8 times 10-6 daltons). DNA infectivity studies by using the calcium phosphate and the DEAE-dextran method gave further evidence that H genomes are defective: no infectious virus was recovered from permissive cells treated with heavy DNA, whereas M genome-infected cells developed cytopathic changes after 11 to 56 days. Defective H genomes were present in the progeny virus two passages after transfection.
TL;DR: The origin of a low molecular weight virus-associated RNA (VA-RNA) was mapped by hybridization of VA-RNA to specific fragments of adenovirus type 2 DNA, obtained after cleavage with three different restriction endonucleases.
01 Jan 1975
TL;DR: In this article, the authors discuss the role of RNA-directed DNA polymerase (R-PDP) in both the virus life cycle and virus-induced transformation of the host cell.
Abstract: RNA tumor viruses are useful tools for the study of oncogenesis because they rapidly induce tumors in animals and efficiently transform cells in culture. These viruses are distinguished by certain morphological features (Bernhard, 1960; Sarker et al., 1971a), an exceptionally large single-stranded RNA genome (about 30,000 nucleotides, Duesberg, 1970) and an RNA-directed DNA polymerase which transcribes the viral genome into single- and double-stranded DNA (Baltimore, 1970; Temin and Mizutani, 1970; Temin and Baltimore, 1972). This transcription, the mechanism by which it occurs, the fate of its products in the infected cell, and the role of the products in both the viral life cycle and virus-induced transformation of the host cell are the principal subjects of our discussion.
TL;DR: Evidence is presented for five or six previously undetected heterokaryon incompatibility (het) loci, bringing to about ten the number of such genes known in Neurospora crassa the number that were detected using chromosome duplications, on the basis of properties previously known for het genes in duplications.
Abstract: Evidence is presented for five or six previously undetected heterokaryon incompatibility (het) loci, bringing to about ten the number of such genes known in Neurospora crassa. The genes were detected using chromosome duplications (partial diploids), on the basis of properties previously known for het genes in duplications. Duplications homozygous for het genes are usually normal in growth and morphology, whereas those heterozygous are strikingly different. The heterozygotes are inhibited in their initial growth, produce brown pigment on appropriate medium, and later "escape" from their inhibition, as a result of somatic events, to produce wild-type growth. - Five normal-sequence strains were crossed to 14 duplication-producing chromosome rearrangements, and the duplication progeny were examined for properties characteristic of duplications heterozygous for known het genes. Each cross produced duplications for a specific region of the genome, depending on the rearrangement. Normal-sequence strains were wild types from nature, chosen from diverse geographic locations to serve as sources of genetic variation. - The duplication method was very effective. Most of the longer duplications uncovered het genes. The genes are: het-5 (on linkage group IR, in the region covered by duplications produced using rearrangement T (IR LEADS TO VIR)NM103), het-6 (on IIL, covered by T(IIL LEADS TO VI)P2869 and T(IIL LEADS TO IIIR)AR18 duplications), het-7 (tentatively assigned to IIIR, T(IIIR LEADS TO VIL)D305), het-8 (VIL, T(VIL LEADS TO IR)T39M777), het-9 (VIR LEADS TO IVR)AR209), and het-10 (VIIR, T(VIIR LEADS TO IL)5936.
TL;DR: A method for specific radiolabeling of adjacent fragments was employed to establish the fragment order, and this technique may be useful for ordering the fragments produced by digestion of complex DNAs.
Abstract: Digestion of polyoma viral DNA with a restriction enzyme from Haemophilus aegyptius generates at least 22 unique fragments. The fragments have been characterized with respect to size and physical order on the polyoma genome, and the 5' to 3' orientation of the (+) and (-) strands has been determined. A method for specific radiolabeling of adjacent fragments was employed to establish the fragment order. This technique may be useful for ordering the fragments produced by digestion of complex DNAs.
TL;DR: By using low salt extraction and sodium dodecyl sulfate-phenol deproteinization, six to eight low molecular weight homogeneous RNA species were isolated from chick embryo chromatin and mouse myeloma chromatin, and the redundancy of genes for 18S, 28S, and 5S rRNA and tRNA was determined.
Abstract: Several methods of preparing low molecular weight RNA from chick embryo chromatin have been examined. Traditional methods for dissociating chromatin utilizing high concentrations of salt (greater than 2 M) followed by high-speed centrifugation resulted in very low yields of RNA. Increased yields of RNA were obtained by treating chromatin at lower salt concentration (0.2-0.5 M). By using low salt extraction and sodium dodecyl sulfate-phenol deproteinization, six to eight low molecular weight homogeneous RNA species were isolated from chick embryo chromatin and mouse myeloma chromatin. In the myeloma system, all these RNAs are metabolically stable. Each component is homogeneous as examined by gel electrophoresis and hybridizes with mouse DNA at a rate consistent with a single species. There are multiple gene copies for these RNA species in the mouse genome, varying from 100 to 2000 copies for the different species. One of these RNAs is identical with 5S rRNA. In addition, the redundancy of genes for 18S, 28S, and 5S rRNA and tRNA was determined. Approximately 300 copies for 18 and 28S rTRNA and 500 copies for 5S rRNA were found. tRNAs were on an average 110-fold redundant with about 55 different species measured.
TL;DR: Several lines of evidence are presented which support the contention that chromatin may be dissociated, fractionated, and reconstituted without altering the compositional, structural, or transcriptional integrity of the genome.
Abstract: Several lines of evidence are presented which support the contention that chromatin may be dissociated, fractionated, and reconstituted without altering the compositional, structural, or transcriptional integrity of the genome. The similar compositions of native and reconstituted chromatins are suggested by the absence of significant differences in their protein/DNA ratios and in the polyacrylamide gel electrophoretic profiles of their histones and nonhistone chromosomal proteins. Criteria for fidelity of genome structure in reconstituted chromatin include binding of reporter molecules with specificity for the minor groove of DNA, binding of histones, number of sites available for addition of nucleotides, and circular dichroism spectra. When the transcriptional activities of native and reconstituted chromatins were compared under conditions where reinitiation is prohibited, significant changes were not observed. Taken together, the present results strongly suggest, but do not conclusively establish, fidelity of chromatin reconstitution.
TL;DR: Analysis of [35S]methionine-labeled tryptic peptides of the large proteins induced by temperature-sensitive mutants of Semliki Forest virus found that two proteins with molecular weights of 78,000 and 86,000 from ts-1-infected cells did not contain the peptide of the virion structural proteins.
Abstract: Analysis of [35S]methionine-labeled tryptic peptides of the large proteins induced by temperature-sensitive mutants of Semliki Forest virus was carried out. The 130,000-molecular-weight protein induced by ts-2 and ts-3 mutants contained the peptides of capsid protein and of both major envelope proteins E1 and E2. The ts-3-induced protein with molecular weight of 97,000 contained peptides of the capsid and envelope protein E2 but not those of E1. Two proteins with molecular weights of 78,000 and 86,000 from ts-1-infected cells did not contain the peptides of the virion structural proteins. They are evidently expressions of the nonstructural part of the 42S RNA genome of Semliki Forest virus.
TL;DR: A mechanism of evolution is proposed that involves two sequential duplications of an ancestral genome, followed by mutation and divergence of function of replicate genes.
Abstract: Many pairs of genes whose gene products are functionally related lie either 90 degrees or 180 degrees apart on the circular map of the E. coli chromosome. A mechanism of evolution is proposed that involves two sequential duplications of an ancestral genome, followed by mutation and divergence of function of replicate genes.
TL;DR: It is likely that temporal ordering of replication exists for most genes in the yeast genome, and sites for initiation of DNA replication occur at fairly specific regions along yeast chromosomal DNA moleucles, and are activated at predetermined times in the DNA synthesis period.
TL;DR: It is proposed that the repetitive sequences are the keratin coding sequences and that the unique sequences correspond to untranslated regions.
Abstract: Embryonic chick feather keratins are a family of homologous polypeptide chains. The mRNA coding for these has been obtained in a pure state and transcribed into complementary DNA (cDNA) using the reverse transcriptase from avian myeloblastosis virus. Studies on the kinetics of hybridisation and reannealing of cDNA indicate that there are 25-35 different keratin mRNA species in the embryonic chick feather, and a total of 100-240 keratin genes in the chick genome. Each keratin gene contains both a unique and a repetitive sequence. It is proposed that the repetitive sequences are the keratin coding sequences and that the unique sequences correspond to untranslated regions.
TL;DR: There is little structural differentiation between the chromosomes of the three species, no effective isolation barrier to gene-flow between them, and it is concluded that they are closely related phylogenetically, having possibly evolved from a common progenitor.
Abstract: With a view to eclucidating chromosome relationships between Lolium perenne (Lp), L. multiflorum (Lm) and Festuca pratensis (Fp), chromosome pairing in different diploid (2n=14), auto-allotriploid (2n=3x=21), trispecific (2n=3x=21), amphidiploid (2n=4x=28) and auto-allohexaploid (2n=6x=42) hybrids between them was analysed. At all these levels of ploidy there was very good chiasmate pairing between the chromosomes of the three species and, on the whole, there was little evidence of preferential pairing of the chromosomes of a particular species in the triploid, tetraploid and hexaploid hybrids. A critical test for this also came from the synaptic ability of the chromosomes of the single genome with those of the duplicated genome in the auto-allotriploids which formed predominantly trivalents with 2, 3 or even 4 chiasmata. Moreover, the homology between the Lp and Lm chromosomes seems strong enough to pass the discrimination limits of the B-chromosomes which do not suppress homoeologous pairing in the Lp LmLm triploid and LpLm diploid hybrids. — The triploids having two genomes of a Lolium species and one of F. pratensis had some male and female fertility which suggested genetic compatibility of the parental chromosomes resulting, presumably, in compensation at the gametic level. Also, the occurrence of comparable chiasma frequencies in the auto-allotriploids and trispecific hybrids showed that they were not markedly affected whether two doses of one genome and one of the other or all the three different genomes from the three species were present. From the trend of chromosome pairing in all these hybrids it is concluded that there is little structural differentiation between the chromosomes of the three species, no effective isolation barrier to gene-flow between them, and that they are closely related phylogenetically, having possibly evolved from a common progenitor. Taxonomic revision of the two Lolium species is suggested.
TL;DR: Defective DNAs, isolated from mouse cells after infection with a clonally purified stock of defective polyoma virus, have been found to consist of nucleotide sequences from about 17% of the wild-type polyoma genome, tandemly repeated two to six times.
Abstract: Defective DNAs, isolated from mouse cells after infection with a clonally purified stock of defective polyoma virus, have been found to consist of nucleotide sequences from about 17% of the wild-type polyoma genome, tandemly repeated two to six times. These sequences come from the region of the viral DNA which contains the origin of DNA replication and the 5′ ends of early and late stable mRNAs.
TL;DR: It is suggested that a loss of about 30% of the genomic sequences of MEV with a concomitant gain of roughly equal amounts of rat-specific sequences in a genetically stable recombinant state led to the formation of Ki-MSV.
Abstract: Summary
The technique of virus RNA-cellular DNA hybridization in solution with DNA excess was used to compare the nucleotide sequences of the 70S RNA genome of the Kirsten mouse sarcoma virus (Ki-MSV) with that of mouse erythroblastosis virus (MEV) which gave rise to Ki-MSV after in vivo propagation in rat. It is suggested that a loss of about 30% of the genomic sequences of MEV with a concomitant gain of roughly equal amounts of rat-specific sequences in a genetically stable recombinant state led to the formation of Ki-MSV.
TL;DR: Cells derived from tumors induced in "nude" mice after injection of cells that were hybrids between mouse peritoneal macrophages and simian virus 40-transformed human cells were found to retain the human chromosome 7 carrying the SV40 genome.
Abstract: Cells derived from tumors induced in "nude" mice after injection of cells that were hybrids between mouse peritoneal macrophages and simian virus 40 (SV40)-transformed human cells were found to retain the human chromosome 7 carrying the SV40 genome, and indicate that the presence of human chromosome 7 carrying the SV40 genome is responsible for the expression of the tumorigenic phenotype in the hybrid cells.
TL;DR: Nucleic acid sequences complementary to single-stranded DNA prepared from the endogenous chicken (C-type) RNA tumor virus, RAV-O, were detected in nuclear DNA from five different avian species, suggesting that most if not all species of fowl containRNA tumor virus sequences in their DNA.
TL;DR: Polyacrylamide-slab gel electrophoresis of peroxidases of different Triticum and Aegilops species and of nullisomic–tetrasomic lines of Chinese spring wheat showed that T. aestivum chromosomes 7D, 4B, and 7A are the carriers of genes coding the synthesis of per oxidase a, peroxidsase c, and peroxIDase d, respectively.
Abstract: Polyacrylamide-slab gel electrophoresis of peroxidases of different Triticum and Aegilops species and of nullisomic–tetrasomic lines of Chinese spring wheat showed that T. aestivum chromosomes 7D, 4B, and 7A are the carriers of genes coding the synthesis of peroxidase a, peroxidase c, and peroxidase d, respectively. The indirect effect of modified chromosome systems and a special effect of chromosome 5B on peroxidase synthesis have also been observed. The chromosomal and genomic origin of the three other peroxidases (b, e, and f) detected in common wheat could not be definitively established.
TL;DR: The sequence homology and similarity in genomic organization suggest a close relationship between these papovaviruses.
Abstract: A number of hybridization techniques have been used to assess the homology between the genomes of BK virus (BKV) and simian virus 40 (SV40) A noncontiguous set of homologous sequences has been localized primarily within the late region of the SV40 genome, and these sequences presumably account for the cross-reaction between V-antigens of the two viruses The reason for the relatively strong crossreaction between SV40 and BKV T-antigens is still unclear The sequence homology and similarity in genomic organization suggest a close relationship between these papovaviruses
TL;DR: A better understanding of the functions of the viral genome in infected and transformed cells will be achieved through studies with temperature-sensitive mutants of herpesviruses since, theoretically, any essential gene function can be affected by mutants of this type.
Abstract: The processes involved in herpesvirus replication, latency, and oncogenic transformation, have, in general, been rather poorly defined. A primary reason for this is the size and complexity of the herpesvirus genome. Undoubtedly, a better understanding of the functions of the viral genome in infected and transformed cells will be achieved through studies with temperature-sensitive (ts) mutants of herpesviruses since, theoretically, any essential gene function can be affected by mutants of this type.
TL;DR: Progress in understanding the much more complex molecular events that regulate differentiation in eukaryotic cells will require the sustained and collab orative efforts of many research groups working on a few advantageous systems.
Abstract: There exists a fairly detailed understanding of the mechanism and regulation of RNA and protein biosynthesis in bacterial cells. This is a direct result of intensive work by a large number of laboratories on a relatively few, especially favorable, systems: bacteriophages T4, T7, and ,\: the RNA phages: and the lac, am, his, and trp operons in Escherichia coli and related bacteria () -4). Progress in understanding the much more complex molecular events that regulate differentiation in eukaryotic cells will, l ikewise, require the sustained and collab orative efforts of many research groups working on a few advantageous systems. A wide variety of genetic, biochemical, and morphologic approaches will have to be used, and no one organism or system will be ideal for all these types of studies. The cellular slime mold, Dictyostelium discoideum, offers many advantages for a detailed study of differentiation in a relatively simple system. Dictyostelium is a eukaryotic protist easily cultivated as single cells either axenically or in association with bacteria (5-7). Isolated cells form clones with an efficiency of nearly 100%. The nuclear DNA genome is one fiftieth the complexity of that of mammalian cells (810) and the mode of mRNA biosynthesis is conserv ative and involves a much shorter nuclear precursor than in mammalian cells