Showing papers on "Gene expression published in 1972"

Function of peptide antibiotics in sporulation.

Abstract: Tyrothricin specifically inhibits RNA synthesis in growing cultures of Bacillus brevis as well as purified RNA polymerase. This suggests that the peptide antibiotic may function in the regulation of gene transcription during the transition from vegetative growth to sporulation.

Cistron specific translation control protein in Escherichia coli.

Abstract: GENE expression may be controlled during translation by ribosomal selection of mRNAs or even individual cistrons. Escherichia coli initiation factors associated with ribosomes affect the binding of ribosomes to mRNA1,2; initiation factor IF3, for instance, influences the specificity of mRNA-ribosome interaction3,4. IF3 activity has been separated into several fractions which show various specificities for different mRNA cistrons4–9. An important problem is the possibility of intracellular changes in IF3 activity10–12. From uninfected E. coli, we have now isolated a protein which changes the specificity of IF3 toward different mRNAs; we call this interference factor i. Pure factor i binds to IF3 and specifically affects the translation of T4 and MS2 RNA. Whereas the initiation of translation of the MS2 coat protein cistron is inhibited by factor i, the synthetase cistron—when available—is more rapidly initiated in the presence of factor i. The overall translation of T4 mRNA appears unchanged by factor i, but certain cistrons are stimulated at the expense of others. Interfering factors such as factor i could be important in controlling translation in E. coli.

Chapter 1 The Structure of Transcriptional Units In Eukaryotic Cells

Abstract: Publisher Summary This chapter discusses the difference between eukaryotes and prokaryotes in many respects. First, they have then nuclei separated by a membrane from the cytoplasm. This membrane effectively separates transcription, which takes place in the nucleus, from translation, which proceeds mainly in the cytoplasm. Thus, transcription and translation in eukaryotes are uncoupled and for this reason an additional step in gene expression appears— namely, mRNA transport. Second, in eukaryotes the process of the regulation of gene expression is complicated. Various cells differ greatly in their properties, and these differences are stable and do not depend on the conditions of the medium— that is, the cells are differentiated. Third, the chromosomes in eukaryotes contain many proteins. In particular, the strongly basic proteins, histones, are complexed with the DNA. This may be connected with the appearance of differentiation and the general complication of the regulatory processes. This chapter describes the patterns of transcription in eukaryotic cells. Different models of the transcriptional unit in eukaryotic cell are discussed in the chapter to describe the nature of dRNA2 or dRNA that is degraded inside the cell nucleus. General aspects of the regulation of transcription in eukaryotes and the role of chromosomal protein are also discussed in this chapter.

Interferon treatment inhibits Mengo RNA and haemoglobin mRNA translation in cell-free extracts of L cells.

Abstract: THE effects of interferon on gene expression are still in debate To explain the block in the multiplication of both DNA and RNA viruses, it was proposed that interferon affects the translation of viral mRNA, but not that of cellular or synthetic mRNAs1–5 Because active cell-free systems which translate purified mRNA were not available at the time, evidence for these effects remained suggestive but inconclusive Very recently, marked inhibitions of virion associated transcriptases in interferon-treated cells have been reported6,7; but again, the proposed effects of interferon treatment on transcription6–8 have not been demonstrated in cell-free systems As a cell-free system from interferon-sensitive mouse L cells, active for the in vitro translation of natural mRNAs, is now available9–11 we have reinvestigated the influence of interferon treatment on the translation of viral and cellular mRNAs

RNA Stimulated by Indole Acetic Acid

Abstract: THE stimulation of RNA synthesis in plant cells by auxins1,2 may be due, in part, to gene derepression, since chromatin isolated from hormone-treated cells is a better template. Mathysse and Phillips3 demonstrated that an acceptor protein for auxin can interact with the chromatin to derepress the genome. In their system the hormone and protein do not affect the rate of RNA synthesis if pure DNA. is used as a template. However, the actual mechanism of auxin on RNA synthesis by isolated RNA polymerase system has yet to be elucidated.

Gene expression by constitutive mutants of coliphage lambda

Abstract: Mutations c17 and ri c, which permit constitutive expression of genes O and P and transcriptional activation of λ DNA replication, act as new promoters since they map outside the immunity region and direct rightward transcription in the presence of repressor. In the λc17 P -or λri cP- lysogens, this constitutive transcription is restricted to the O-P region, and is at least one order of magnitude lower than that for an induced λP -lysogen. The operator-constitutive mutants v2 and v1v3 give very low levels of constitutive transcription from the l and r strands, respectively.

The macronuclear envelope ofTetrahymena pyriformis GL in different physiological states : V. Nuclear pore complexes - A controlling system in protein biosynthesis?

Abstract: A simple formula is derived to calculate the nucleocytoplasmic RNA-Efflux per nuclear Pore complex per min (REP-rate) which is generally applicable both for “growing” and “stationary” eukaryotic cells. In actively growing cells this REP-rate is mainly dependent on the cytoplasmic RNA-pool, the number of RNA-transporting pores, and the growth constant of RNA. These parameters are determined in logarithmicTetrahymena pyriformis GL. In this organism, 45 molecules both of the larger ribosomal RNA (25s rRNA) and of the smaller (17s rRNA) are transported per pore per min from nucleus to cytoplasm. “Pulse-label” experiments with3H-uridine indicate that the 25s rRNA is obviously transferred more slowly to the cytoplasm than the 17s rRNA. We postulate a “gating hypothesis” on the regulation of the nucleocytoplasmic RNA-efflux by nuclear pore complexes. This gating hypothesis suggests that nucleopores are controlling points of secondary importance in the sequence of gene expression, and do not directly control the cytoplasmic protein synthesis in eukaryotic cells.

Tissue specificity of genetic transcription.

Abstract: The basic biochemical differences which exist between cells in animal tissues are reflections of characteristic patterns of proteins. The process (es) of differentiation, therefore, may be described as the process (es) whereby cells, presumably of identical genotype, develop into phenotypically distinct entities which reflect characteristic patterns of gene activity. The differential genetic expression which initiates these different protein patterns at different stages of development and in different tissues can involve regulation of the synthesis of the characteristic protein patterns at any or all of the following steps: 1) Differential RNA transcription including the possibility of specificity and efficiency differences in RNA polymerase; 2) Non-random stabilization and maturation of potential messenger RNA within the pool of unstable heterogeneous nuclear RNA including modifications in maturation, i. e., Poly-A termination; 3) Regulation of the transport of “mature” potential messenger RNA from the nucleus to the cytoplasm including physiological and hormone mediated non random alterations in this specific transport process; 4) Differential stabilities of messenger RNA molecules in the cytoplasm including modulation involving specific polypeptide processing; 5) Modulation of the translational efficiency of messenger RNA-ribosome complexes actively involved in protein synthesis. 6) Differential stability of the protein products.

Human Leukemic Cells: Cytochemical Studies on Nuclear Proteins*

Abstract: The DNA:histone ratios have been determined by quantitative cytochemical analyses of individual cells in populations of human lymphocytic cells derived in continuous culture from the peripheral blood buffy coats of patients with acute leukemia or infectious mononucleosis. These populations of lymphocytic cells were quite similar with respect to the Feulgen-DNA and protein content per cell. The close association between DNA and histone was reflected in their similar patterns of distribution in fixed and stained cells; and further evidenced by similarities in the DNA: histone ratios characteristic of these different populations of lymphocytic cells. — Chemical acetylation and methylation of nuclear proteins of these cell populations exhibited some quantitative differences. The chemically acetylated histone content was less, and chemically methylated histone content was greater in cells derived from acute leukemia or infectious mononucleosis than in normal human lymphocytes. These quantitative differences in chemical acetylation and methylation may contribute to specific structural alterations in these histones which modify their functional capacity with respect to interactions with DNA. Such alterations may relate to differences in gene expression as reflected, for example, by the biological and biochemical differences among these human lymphocytic cells.

Bacterial Gene Expression in Mammalian Cells

Abstract: Summary Bacteriophage, lambda and its transducing derivatives were used to infect human fibroblasts. Transcription of the bacteriophage genome was detected by hybridization with lambda DNA. Lambda-specific RNA (0.2 %) reached a maximum four days after infection. Translation was detected by the use of lambda carrying the galactose operon of E. coli. Human fibroblasts from a galactosemic patient, lacking the ability to make active α-D-galactose-1-phosphate uridyl transferase, produce the transferase enzyme following infection with the transducing phage.

Rna and dna tumor viruses--mechanism of cell transformation and role in human cancer

Abstract: Publisher Summary This chapter focuses on RNA and DNA tumor viruses and their role in human cancer. Viruses are major causes of cancer in animals, but the extent of their role in human cancer is unknown. Studies utilizing molecular hybridization have contributed much to the understanding of tumor virus gene expression and have provided the methodology and nucleic acid reagents so that human tumors can be analyzed for viral genetic information. It is now possible to test each of the approximately 600 known viruses that infect man and animals for their possible involvement in a particular neoplasm or other human disease by relatively simple hybridizations procedures. The chapter discusses the recent progress in understanding the mechanism of cell transformation by DNA and RNA tumor viruses, and the development and utilization of molecular hybridization for the detection of viral nucleic acid sequences in virus-infected and transformed animal cells and in human cancer. The chapter describes the mechanism of cell transformation by oncogenic DNA viruses. An analysis of human cancers for DNA tumor virus genetic information by molecular hybridization is also presented in the chapter.