Showing papers on "Gene expression published in 1971"

Bacterial Virus Gene Expression in Human Cells

Abstract: Human fibroblasts, from a patient with congenital lack of α-D-galactose-1-phosphate uridyl transferase activity, have been infected with transducing bacteriophage that harbours either wild type or defective transferase gene. Infection only by the former phage initiates transferase synthesis.

Tissue differences in antigenic properties of non-histone protein-DNA complexes

Abstract: THAT DNA and histones are not tissue specific1,2 implies that other components of chromatin may be responsible for the tissue specific control of eukaryotic gene expression. We now report studies of the antigenic properties of non-histone protein-DNA complexes isolated in an undissociated state from native chromatin and compare these with the properties of native chromatin. Because DNA is a very weak immunogen3, the antigenic determinants in these preparations should be principally caused by the protein components.

Nucleolar-derived ribonucleic acid in chromosomes, nuclear sap, and cytoplasm of chironomus tentans salivary gland cells

Abstract: The distribution of monodisperse high molecular weight RNA (38, 30, 28, 23, and 18S RNA) was studied in the salivary gland cells of Chironomus tentans. RNA labeled in vitro and in vivo with tritiated cytidine and uridine was isolated from microdissected nucleoli, chromosomes, nuclear sap, and cytoplasm and analyzed by electrophoresis on agarose-acrylamide composite gels. As shown earlier, the nucleoli contain labeled 38, 30, and 23S RNA. In the chromosomes, labeled 18S RNA was found in addition to the 30 and 23S RNA previously reported. The nuclear sap contains labeled 30 and 18S RNA, and the cytoplasm labeled 28 and 18S RNA. On the basis of the present and earlier analyses, it was concluded that the chromosomal monodisperse high molecular weight RNA fractions (a) show a genuine chromosomal localization and are not due to unspecific contamination, (b) are not artefacts caused by in vitro conditions, but are present also in vivo, and (c) are very likely related to nucleolar and cytoplasmic (pre)ribosomal RNA. The 30 and 23S RNA components are likely to be precursors to 28 and 18S ribosomal RNA. The order of appearance of the monodisperse high molecular weight RNA fractions in the nucleus is in turn and order: (a) nucleolus, (b) chromosomes, and (c) nuclear sap. Since both 23 and 18S RNA are present in the chromosomes, the conversion to 18S RNA may take place there. On the other hand, 30S RNA is only found in the nucleus while 28S RNA can only be detected in the cytoplasm, suggesting that this conversion takes place in connection with the exit of the molecule from the nucleus.

Aryl hydrocarbon hydroxylase induction in cell culture as a function of gene expression gene expression

Abstract: For the past several years we have been interested in the mechanisms regulating microsomal enzyme induction in mammalian cells.'-'' These mixedfunction oxygenases12 are important in the metabolism of drugs, insecticides, carcinogens, and many lipophilic endogenous substrates, such as steroids, fatty acids, bilirubin, indoles, thyroxine, sympathomimetic amines, cholesterol, and hemin.13 The levels of these enzymes are very sensitive to changes in the environment of the animal and vary with age, sex, and species difference~ , '~ nutritional and hormonal ~ariations, '~ circadian rhythmicity,\" and exposure to pharmacologically active compound^,'^ insecticide^,'^ and softwood bedding.16 Thus, the intensity and duration of drug action and the rate of metabolism of these normal body substrates are intimately related to changes in the levels of these enzymes. Aryl hydrocarbon hydroxylase, also called benzpyrene hydroxylase, is an example of the mixed-function oxidases. We have extensively studied the induction of this hydroxylase in ~ i w \" ~ * ' ~ and in cell ~ u l t u r e . ' ~ ' ~ ~ ~ ' FIGURE 1 illustrates the hydroxylase assay' used in an in vitro system.* The membranebound enzyme as the cellular or tissue homogenate or the microsomal fraction, in the presence of NADPH, NADH, molecular oxygen, and certain divalent cations, hydroxylates the substrate benzo[alpyrene to more than a dozen alkali-extractable product^.'^ The rate of formation of the 3-hydroxy derivative, which comprises 15 to 30% of all the metabolites, is determined spectrophotofluorometrically and equated with hydroxylase activity. The hydroxylase system is inducible in cell culture by many polycyclic hydrocarbons dissolved in the growth medium and is able to convert all of these same substrates to phenolic products in varying degrees.'\" It is convenient that a major inducer, benz[a]anthracene (BA) ,t and its metabolites do not interfere with the spectrophotofluorometric determination of 3-hydroxybenzo[a]pyrene production in uitro. The number of necessary components in the aryl hydrocarbon hydroxylase system is not certain, but it is important to keep in mind that the \"enzyme activity\" we measure (FIGURE 2) is the result of a multicomponent electron

Genetic expression in whole cells of heterozygous replicative-form molecules of Φ174

Abstract: The role of the parental viral strand in infection with bacteriophage Φ174 has been deduced from both biophysical and biological studies. The viral strand, on entering the cell, is converted to a double-stranded replicative form (RF). This parental RF is bound to the membrane, where the viral strand appears to be physically conserved throughout infection and to be required even at late times. In starved cells, only the RF containing the parental viral strand replicates, semiconservatively. The parental viral strand is conserved in this RF, with each new complementary partner being released in turn in a progeny RF molecule. The parental RF is also responsible for initial messenger RNA synthesis; it is not yet known whether or not it is responsible for all messenger RNA synthesis.

‘Pleiotypic’ and ‘Specific’ Hormonal Control of Gene Expression in Mammalian Cells

Abstract: I should like to propose that regulation by a variety of hormones and other growth-stimulating substances is effected in two ways, which I shall refer to as the ‘pleiotypic’ [1] and ‘specific’ modes of regulation. The pleiotypic control system refers to a coordinated set of reactions which respond in a characteristic way when cellular growth is stimulated by a specific hormone. Some of the reactions under this type of general control are: (1) the uptake of glucose and of various precursors for macromolecular synthesis; (2) RNA synthesis, particularly of ribosomal and transfer RNA; (3) protein synthesis and the state of polysome assembly (probably determined by the initiation reaction); (4) the degradation of intracellular proteins and other macromolecules. Responses in all of the above reactions follow the administration of the steroid hormones, thyroxin, insulin and growth hormone to animals (see [1] for references); similar reactions are regulated when lymphocytes are stimulated by phytohemagglutinin, erythroid cells by erythropoietin, and in other conditions where the growth of certain cells is stimulated by a specific humoral agent. Table 1 lists some of the reaction under pleiotypic control and how they are regulated in specific situations.

Effect of 3′, 5′-Cyclic Amp on Gene Expression in Escherichia Coli

Abstract: The disparity between the known roles of cyclic AMP (cAMP) in bacteria and higher cells has been puzzling. In mammalian cells, as participants of this Symposium have been reminding us, a number of effects are exerted independent of the transcription process, presumably by activating latent enzymatic machinery-or possibly latent messenger RNA. In contrast, for the best characterized systems in bacteria, cyclic AMP helps to determine the repertoire of gene transcription open to the cell [1–5].

The tomato mutant 'curl"

Abstract: A B S T R A C T The dominant tomato mutant 'Curl' differs from normal plants in several striking respects including the following: misshapen laminar structures such as leaves, sepals, and petals; stunted petiole and rachis; and persistent growth of blade and stem tissue from the adaxial surface of the rachis. These tissues as well as others which appear morphologically normal show gross histological abnormalities. Also evident in sections of mutant tissue is the appearance of areas containing numerous crystalline inclusions and a lack of bodies showing a stainable starch reaction in palisade and mesophyll of leaves and in endodermis and pith cells of the stem. ONE SUCCESSFUL approach to the study of the functioning of genetic material has involved the use of mutants to investigate the control of the enzymes of lactose utilization by the haploid Escherichia coli cell (Jacob and Monod, 1961). To extend our understanding of the control of genetic information and of the development of form from this information to diploid organisms, single gene mutants which produce marked morphological characteristics may be useful experimental materials. In a study of the expression of a gene producing a distinctive phenotype, at least two sequential components can be theoretically delineated (modified from Ebert and Kaighn, 1966): differentiation and morphogenesis. Differentiation is the appearance of change in the metabolism of cellular molecules such as nucleic acids or proteins as a consequence of the expression of different segments of the cell's one-dimensional DNA sequence. Morphogenesis includes the phenomenon of shaping the three-dimensional structures of cells by folding and aggregation of one-dimensional gene products which leads eventually to externally visible, three-dimensional phenotypes. Recognizing these two aspects of gene expression, a genetic study of the control of the expression of hereditary information manifested morphologically would then involve first, an initial characterization of the morphology and histology of normal and mutant; second, identification of differences at the level of molecules; and third, evidence for the mechanism of the externally visible effect. Higher plants are well-suited for studies of differentiation and morphogenesis, particularly because of their permanently embryonic regions,

CHAPTER 6 – Regulation of Gene Expression in Mammalian Cells

Abstract: Publisher Summary This chapter focuses on the regulation of gene expression in mammalian cells. In mammalian tissues, in fact in most eukaryotic tissues, a recognized predominant action of cyclic AMP (cAMP) is the stimulation of enzymic phosphokinase activities that are responsible for the phosphorylation of proteins. It has been proposed that hormones that activate adenyl cyclase regulate gene activity via the cAMP promotion of histone phosphorylation, the latter permitting more efficient gene transcription than does its non-phosphorylated form. Many attempts have been made to demonstrate that hormones exert their effects on gene expression at the level of gene transcription, analogous to the action of inducers on the lactose operon in Escherichia coli. An integral part of the regulatory mechanisms in prokaryotes is the rapid turnover of messenger RNA molecules. Thus, when specific gene transcription is repressed, the concentration of specific RNA template rapidly falls and the synthesis of the specific protein ceases. Furthermore, the rate of specific protein synthesis is frequently determined only by the concentration of specific template RNA. Any system in which a paradoxical stimulation of specific protein synthesis is caused by inhibitors of RNA synthesis is quite likely to be subject to a posttranscriptional regulation of gene expression. Therefore, it may be that the posttranscriptional regulation of gene expression is a general mechanism found in many developing and inducible systems of eukaryotes.