A correlation of changes in host and T 4 bacteriophage specific RNA synthesis with changes of DNA-dependent RNA polymerase in Escherichia coli infected with bacteriophage T 4

Endometrial cancer

Although endometrial cancer management remains challenging, a deeper understanding of the genetic diversity as well as the drivers of the various pathogenic states of this disease has led to development of divergent management approaches in an effort to improve therapeutic precision in this complex malignancy. This comprehensive review provides an update on the epidemiology, pathophysiology, diagnosis and molecular classification, recent advancements in disease management, as well as important patient quality-of-life considerations and emerging developments in the rapidly evolving therapeutic landscape of endometrial cancers.

Novel human immunomodulatory T cell receptors and their double-edged potential in autoimmunity, cardiovascular disease and cancer

In the last decade, approaches based on T cells and their immunomodulatory receptors have emerged as a solid improvement in treatments for various types of cancer. However, the roles of these molecules in the therapeutic context of autoimmune and cardiovascular diseases are still relatively unexplored. Here, we review the best known and most commonly used immunomodulatory T cell receptors in clinical practice (PD-1 and CTLA-4), along with the rest of the receptors with known functions in animal models, which have great potential as modulators in human pathologies in the medium term. Among these other receptors is the receptor CD69, which has recently been described to be expressed in mouse and human T cells in autoimmune and cardiovascular diseases and cancer. However, inhibition of these receptors individually or in combination by drugs or monoclonal antibodies generates a loss of immunological tolerance and can trigger multiple autoimmune disorders in different organs and immune-related adverse effects. In the coming decades, knowledge on the functions of different immunomodulatory receptors will be pivotal for the development of new and better therapies with less harmful side effects. In this review, we discuss the roles of these receptors in the control of immunity from a perspective focused on therapeutic potential in not only cancer but also autoimmune diseases, such as systemic lupus erythematosus, autoimmune diabetes and rheumatoid arthritis, and cardiovascular diseases, such as atherosclerosis, acute myocardial infarction, and myocarditis.

Polyfunctional HIV-1 specific response by CD8+ T lymphocytes expressing high levels of CD300a

CD300a receptor is found on different CD8+ T cell subsets and its expression has been associated to a more cytotoxic molecular signature. CD300a has an important role in some viral infections and its expression levels are known to be modulated by human immunodeficiency virus (HIV)−1 infection on several cell types. The main objective of this work was to investigate CD300a expression and its regulation during HIV-1 specific CD8+ T cell responses. CD300a receptor expression was analysed by multiparametric flow cytometry on CD8+ T lymphocytes from HIV negative donors, naive HIV-1+ individuals and HIV-1+ subjects under suppressive combined antiretroviral therapy (cART). HIV-1 specific CD8+ T cell response was studied by stimulating cells with HIV-1 derived peptides or with a Gag HIV-1 peptide. Our results showed that HIV-1 specific CD8+ T cells expressing higher levels of CD300a were more polyfunctional showing an increased degranulation and cytokine production. Moreover, we observed an up-regulation of CD300a expression after Gag HIV-1 peptide stimulation. Finally, our results demonstrated an inverse correlation between CD300a expression on CD8+ T lymphocytes and HIV disease progression markers. In conclusion, CD300a expression is associated to a better and more polyfunctional HIV-1 specific CD8+ T cell response.

The yin and yang of co-inhibitory receptors: toward anti-tumor immunity without autoimmunity

Co-inhibitory receptors are important regulators of T-cell function that define the balance between tolerance and autoimmunity. The immune regulatory function of co-inhibitory receptors, including CTLA-4, PD-1, TIM-3, TIGIT, and LAG-3, was first discovered in the setting of autoimmune disease models, in which their blockade or deficiency resulted in induction or exacerbation of the disease. Later on, co-inhibitory receptors on lymphocytes have also been found to influence outcomes in tumor and chronic viral infection settings. These receptors suppress T-cell function in the tumor microenvironment (TME), thereby making the T cells dysfunctional. Based on this observation, blockade of co-inhibitory receptors (also known as checkpoint molecules) has emerged as a successful treatment option for a number of human cancers. However, severe autoimmune-like side effects limit the use of therapeutics that block individual or combinations of co-inhibitory receptors for cancer treatment. In this review we provide an overview of the role of co-inhibitory receptors in autoimmunity and anti-tumor immunity. We then discuss current approaches and future directions to leverage our knowledge of co-inhibitory receptors to target them in tumor immunity without inducing autoimmunity.

Integrative network modeling reveals mechanisms underlying T cell exhaustion

Failure to clear antigens causes CD8⁺ T cells to become increasingly hypo-functional, a state known as exhaustion. We combined manually extracted information from published literature with gene expression data from diverse model systems to infer a set of molecular regulatory interactions that underpin exhaustion. Topological analysis and simulation modeling of the network suggests CD8⁺ T cells undergo 2 major transitions in state following stimulation. The time cells spend in the earlier pro-memory/proliferative (PP) state is a fixed and inherent property of the network structure. Transition to the second state is necessary for exhaustion. Combining insights from network topology analysis and simulation modeling, we predict the extent to which each node in our network drives cells towards an exhausted state. We demonstrate the utility of our approach by experimentally testing the prediction that drug-induced interference with EZH2 function increases the proportion of pro-memory/proliferative cells in the early days post-activation.

Pathogenesis of experimental salmonellosis: inhibition of protein synthesis by cytotoxin

Salmonella cytotoxin present in cell lysates inhibited protein synthesis in both Vero cells and isolated rabbit intestinal epithelial cells. A time-course experiment with Vero cells revealed progressive inhibition of protein synthesis beginning as early as 1 h after exposure to the Salmonella cell lysate. Significant loss of membrane integrity of Vero cells (measured by release of [3H]uridine) did not appear before 24 h. To demonstrate inhibited protein synthesis in intestinal tissue during experimental salmonellosis, we isolated rabbit epithelial cells from Salmonella-infected and control intestinal loops. Measurement of [3H]leucine incorporation showed a similar decrease in protein synthesis in epithelial cells from the Salmonella-infected intestinal loop as that from an adjacent control loop. A similar pattern of protein synthesis inhibition was observed when isolated epithelial cells from normal rabbit intestine were exposed to the Salmonella cell lysate. The inhibited protein synthesis in the intestinal cells provides a molecular basis for the cellular damage caused by Salmonella cytotoxin during experimental salmonellosis.

Phage T4 infection restricts rRNA synthesis by E. coli RNA polymerase

RNA polymerase from T4 infected cells supplemented with E. coli sigma polypeptide has a lower affinity for rRNA promoters than RNA polymerase from uninfected cells. The pattern of transcription by the phage modified polymerase is qualitatively similar to that of the vegetative polymerase in the presence of ppGpp. We suggest that E. coli polymerase holoenzyme normally exists in at least two conformational states, one with a high affinity for rRNA promoters and another with a low affinity, and that T4 infection stabilises the low affinity form.

Effects of bacteriophage T4-induced modification of Escherichia coli RNA polymerase on gene expression in vitro

After T4 bacteriophage infection of E. coli a complex series of events take place in the bacterium, including gross inhibition of host transcription and discrete changes in the classes of the genes of T4 that are transcribed. Accompanying these changes in the pattern of transcription one finds T4-induced changes in the RNA polymerase (EC 2.7.7.6; nucleosidetriphosphate:RNA nucleotidyltransferase). The effects of modified polymerase on transcription can be advantageously analyzed in a DNA-directed cell-free system for protein synthesis. In this system gene activity is measured indirectly by the amounts and types of proteins sythesized. In the DNA-directed cell-free system this modified polymerase, like normal polymerase, transcribes T4 DNA with a high efficiency but transcribes bacteriophage lambda and host DNA very poorly. Polymerase reconstruction experiments show that modification of the alpha subunit of the RNA polymerase is sufficient for inhibition of host transcription. Host transcription is also inhibited in vitro by T4 DNA. This latter type of inhibition is presumed to involve competition between host DNA and T4 DNA for some factor essential for transcription. The T4-modified polymerase transcribes from T4 DNA many of the same genes as normal unmodified polymerase; it also shows a capability for transcribing certain "non-early" T4 genes which is enhanced in the presence of protein-containing extracts from T4-infected cells.

Regulation of early mRNA synthesis after bacteriophage T4 infection of Escherichia coli

Regulation of T4-specific mRNA synthesis was studied during leucine starvation of a leucine-requiring stringent Escherichia coli B strain. This was done by imposing starvation prior to T4 infection and then letting RNA synthesis proceed for different time periods. Rifampin or streptolydigin was added to stop further RNA synthesis, and protein synthesis was restored by addition of leucine. Samples were withdrawn at different times, and the enzyme-forming capacities found that, during conditions which elicit the stringent response in uninfected bacteria, immediate early mRNA is not stringently regulated. This conclusion contradicts the earlier conclusion of others, obtained by measuring incorporation of radioactive uracil; this is explained by the observation of Edlin and Neuhard (1967), confirmed and extended by us to the T4-infected cell, that the incorporation of uracil into RNA of a stringent strain is virtually blocked by amino acid starvation, whereas that of adenine continues at 30 to 50% of the rate seen in the presence of the required amino acid.

Purification and properties of a bacteriophage T5-modified form of Escherichia coli RNA polymerase

A modified form of Escherichia coli RNA polymerase that contains one of the three T5-specific polypeptides known to interact with the host enzyme was purified from bacteriophage T5-infected cells. The properties of this T5-modified enzyme appeared identical to those of the RNA polymerase derived from uninfected non-colicinogenic cells and to a fully active enzyme isolated from T5-infected ColIb+ cells after the limited in vivo transcription of T5 genes allowed by the plasmid had ceased.

Transcription of bacteriophage T4 genome in vitro. Heterogeneity of RNA polymerase in crude extracts of normal and T4-infected Escherichia coli B

In order to obtain RNA polymerase preparations carrying the necessary specificity determinants to transcribe the delayed-early genes of bacteriophage T4, crude extracts of uninfected and T4-infected Escherichia coli were fractionated in glycerol gradients of low ionic strength. In contrast to the reported sedimentation behavior of the purified enzyme, the RNA polymerase activity in crude extracts of normal and infected cells sedimented heterogeneously over a wide range of sedimentation coefficients. When the "heavy" (24-33 S) and "light" (14-20 S) regions of the gradient were precipitated with ammonium sulfate and recentrifuged, the former split into two subfractions, one again sedimenting heavy and the other sedimenting light. The latter did not split under the same conditions. The resulting subfractions from uninfected cell extracts had different thermal thermal stabilities at 50 degrees (half-lives ranging from 2-3 to 25 min) while those from T4-infected cell extracts were very thermolabile (half-life of 1-2 min). All the subfractions were more active on T4 DNA than on calf-thymus DNA. They also formed rifampicin-resistant, RNA chain initiation complexes with T4 DNA. Based on the kinetics of heat inactivation with T4 and calf thymus DNAs as templates and preferential transcription of T4 DNA, it is proposed that the T4-infected cell enzymes prepared as described here harbor heat-labile initiation factor(s). During infection the heavy sedimenting RNA polymerase activity disappears after 2.5 min at 37 degrees. This appears to require phage-specific protein synthesis because (a) it does not happen in the presence of chloramphenicol and (b) it does not happen in T4 ghost-infected cells.

SP62, a viable mutant of bacteriophage T4D defective in regulation of phage enzyme synthesis

SP62 is a mutant of bacteriophage T4D that was discovered because it produces fewer phage than the wild type in the presence of 5-fluorodeoxyuridine. In the absence of phage DNA synthesis, SP62 solubilizes host DNA slower than normal; this may explain the sensitivity to 5-fluorodeoxyuridine. In Escherichia coli B at 37 C in the absence of drugs, SP62 makes DNA at a normal rate and the kinetics of appearance of phage are nearly normal. Under the same conditions, SP62 produces T4 lysozyme (gene e) at a normal rate until 20 min, but then produces it at twice the normal rate until at least 60 min. It has long been known that, when T4 DNA synthesis is blocked (DNA(-) state) in an otherwise normal infection, the synthesis of a number of early enzymes continues beyond the shutoff time of about 12 min seen in the DNA(+) state, but still stops at about 20 min. We have termed the 12-min shutoff event S1 and the 20-min shutoff event S2. We show here that, in the DNA(+) state, SP62 makes four early enzymes normally, i.e., S1 occurs. However, in the DNA(-) state (where S1 is missing), SP62 continues to make dCTPase (gene 56), dCMP hydroxymethylase (gene 42), and deoxynucleotide kinase (gene 1) for at least an hour; this results in production of up to 13 times the normal level of dCTPase at 60 min after infection, or 6 times the DNA(-) level. We conclude that SP62 is defective in the second shutoff mechanism, S2, for these three enzymes. In contrast, SP62 causes premature cessation of dTMP synthetase production in the DNA(-) state; the result is a twofold underproduction of dTMP synthetase. Autoradiograms of pulse-labeled proteins separated by slab-gel electrophoresis in the presence of sodium dodecyl sulfate show that a number of other T4 early proteins, including the products of genes 45, 46, and rIIA, are synthesized longer than normal by SP62 in the DNA(-) state. Few late proteins are made in the DNA(-) state, but in autoradiograms examining the DNA(+) state there is little or no effect of the SP62 mutation on the synthesis of T4 late or early proteins. Circumstantial evidence is presented favoring a role for the gene of SP62 in translation of certain mRNAs. At very high temperatures (above 43 C) in the absence of drugs, phage production, but not DNA synthesis, is much reduced in SP62 infections relative to wild-type T4 infections; this temperature sensitivity is greater on E. coli CR63 than on E. coli B. This property has facilitated recognition of the SP62 genotype and aided in complementation testing and genetic mapping. A later publication will provide evidence that SP62 defines a new T4 gene named regA, which maps between genes 43 and 62.

Stimulation of eukaryotic DNA-dependent RNA polymerase by protein factors

Protein factors that stimulate DNA-dependent RNA polymerase activity in vitro have been purified from Novikoff ascites cells. These factors are not adsorbed by the diethylaminoethylcellulose column used for RNA polymerase purification and appear in the flow-through fraction. They can be fractionated into two classes by chromatography on carboxymethylcellulose. The first peak of activity elutes at 0.1 M NH(4)Cl, is stable to heat treatment of 100 degrees for 5 min, and is designated heat-stable factor; the second peak of activity elutes at 0.3 M NH(4)Cl, is heat labile, and is designated heat-labile factor. Heat-labile factor can be further resolved into two components by chromatography on phosphocellulose. The heat-stable factor and second heat-labile factor stimulate the activity of (Novikoff ascites) RNA polymerase B by several-fold, and appear to function independently. RNA synthesis is stimulated only with native DNA as a template. No stimulation of Escherichia coli RNA polymerase is observed with any of the factors.

Nuclear deoxyribonucleic acid-dependent ribonucleic acid polymerases from Saccharomyces cerevisiae

Two deoxyribonucleic acid (DNA)-dependent ribonucleic acid (RNA) polymerases (I, II) have been solubilized from isolated Saccharomyces cerevisiae nuclei. The enzymes can be separated by chromatography on O-diethylaminoethyl Sephadex. Both enzymes are active with high-molecular-weight nuclear yeast DNA, although RNA polymerase I has a higher affinity for polydeoxy-adenylic-thymidylic acid and RNA polymerase II for denatured DNA. RNA polymerase I is active only with manganese. alpha-Amanitin inhibits only the activity of RNA polymerase II.

Transcription after bacteriophage SPP1 infection in Bacillus subtilis

The role of the host polymerase in Bacillus subtilis infected with phage SPP1 was studied in vivo with regard to production of phage-specific and host-specific ribonucleic acid (RNA) and to phage yield. Evidence is presented that the subunit(s) of B. subtilis RNA polymerase which is sensitive to rifampin and streptolydigin is necessary at all times during infection for phage production. The synthesis of phage RNA and the phage yield in strains resistant to either antibiotic were unaffected by the drug. Host RNA synthesis continued throughout infection; phage-specific RNA never accounted for more than 20% of pulse-labeled RNA at any time during infection.

The temporal expression of T2r + bacteriophage genes in vivo and in vitro

The kinetic order of synthesis of deoxycytidylate deaminase (EC 3.5.4.12), deoxycytidylate hydroxymethylase (EC 2.1.2.b), dihydrofolate reductase (EC 1.5.1.3), 5-hydroxymethyldeoxycytidylate kinase (EC 2.7.4.4), and thymidylate synthetase (EC 2.1.1.b) after infection of Escherichia coli with T2r(+) bacteriophage was found not to correlate with their order of synthesis in an in vitro protein-synthesizing preparation. The in vivo and in vitro synthesis of enzyme-specific messenger RNA measured in the protein-synthesizing preparation preceded each enzyme by about 1 min. Through the use of sheared DNA, it was shown that the thymidylate synthetase gene was most susceptible to a loss in template activity, which suggests that this gene is further removed from its promoter than the other genes are from theirs. With a DNA segment of 2.5 x 10(5) daltons, the synthesis of dihydrofolate reductase alone was obtained, but at a much reduced rate. Translation of the RNA from phage-infected cells treated with chloramphenicol yielded amounts of dihydrofolate reductase and deoxycytidylate hydroxymethylase activities similar to those obtained with RNA from untreated infected cells. These results suggest that the chloramphenicol RNA, which consists primarily of immediate-early RNA, may contain most, if not all, of the information required for the synthesis of phage dihydrofolate reductase and deoxycytidylate hydroxymethylase.