Factor actinomycin

There is a single prokaryotic RNA polymerase that synthesizes all types of RNA in the cell. The core polymerase responsible for making the RNA molecule has the subunit structure Ojpp. A protein factor called sigma (a) is required for the initiation of transcription at a promoter. Sigma factor is released immediately after initiation of transcription. Termination of transcription sometimes requires a protein called rho (p) faaor. This enzyme is inhibited by rifampin. Actinomycin D binds to the DNA preventing transcription. 

Transcription factors (such as TFIID for RNA polymerase II) help to initiate transcription. The requirements for termination of transcription in eukaryotes are not well understood. All transcription can be inhibited by actinomycin D. In addition, RNA polymerase II is inhibited by a-amanitin (a toxin from certain mushrooms). These points are summarized in Table 1-3-1,... 

The induction of PAL activity at the onset of vascular differentiation can be shown by the use of plant tissue cultures (37-39). Xylem cells with secondary and lignified walls are differentiated over a time course of 3-14 days by the application of the plant growth factors naphthylene acetic acid (NAA) and kinetin in the ratio 5 1 (1.0 mg/liter NAA, 0.2 mg/liter kinetin) to tissue cultures of bean cells (Phaseolus vulgaris) (37,40). The time for differentiation varies with the type of culture, solid or suspension, and with the frequency and duration of subculture, but for any one culture it is relatively constant (37,41,42). At the time of differentiation when the xylem vessels form, the activity of PAL rises to a maximum. The rising phase of the enzyme activity was inhibited by actinomycin D and by D-2,4-(4-methyl-2,6-dinitroanilino)-N-methylpropionamide (MDMP) applied under carefully controlled conditions (42). This indicated that both transcription and translation were necessary for the response to the hormones. Experiments using an antibody for PAL and a cDNA probe for the PAL-mRNA have also shown that there is an increase in the amount of transcript for PAL during the formation of lignin when Zinnia mesophyll cells are induced to form xylem elements in culture (Lin and Northcote, unpublished work). 

School the interaction corresponds only to the formation of a colloidal suspension of hydrocarbon particles, stabilized to some extent by DNA. This situation diminishes the significance of such an interaction for carcinogenesis. On the other hand, it does not touch upon the reality of the solubilization of hydrocarbons by free purines and upon the significance of the factors considered as being involved in this phenomenon. Generally speaking, the possibility exists that the nature of the interaction of the aromatic hydrocarbons with the nucleic acids is quite different from the nature of their interaction with the free constituents of these acids. Such a situation has been recently brought into evidence for actinomycin (Reich, E., Science 143, 684 (1964) Pullman, B. Biochim. Biophys. Acta 88, 140 (1964).)... 

Bagni, N., Corsini, E., and Serafini-Fracassini, D., Growth-factor and nucleic acid synthesis in Helianthus tuberosus. I. Reversal of actinomycin D inhibition by spermidine, Physiol. Plant., 24, 112-117, 1971. 

RECEPTOR AGONIST used aS an ANTIPARKINSONIAN AGENT. It iS also a PROLACTIN RELEASE INHIBITOR, cachectin tumour necrosis factor, cactinomycin actinomycin C. cadralazine [ban. inn.jan] has properties similar to hydralazine. It is a VASODILATOR and formerly used as an ANTIHYPERTENSIVE. 

Fig. 1. Time course of cell death parameters in tumor necrosis factor (TNF)-induced apoptosis. Human hepatoma cells (HepG2) were incubated in the presence of 400 nM actinomycin D plus 1.6 ng/ml recombinant human TNF (rhTNF)-a. MTT-dye reduction (parameter of mitochondrial function), lactate dehydrogenase (LDH) release (parameter for cell membrane rupture), and DNA fragmentation (parameter associated with typically apoptotic nuclear changes) were determined over a time period of 24 h. As is characteristic of apoptotic cell death, DNA fragmentation always preceded the other death parameters. Similar findings have been obtained in primary hepatocyte cultures and murine livers...

Fig. 4. Prevention by caspase inhibition of lethaUty due to apoptosis receptor stimulation. Mice were injected with actinomycin D/tumor necrosis factor (ActD/TMF) (circle) or anti-CD95 antibody (squares) with (open symbols) or without (solid symbols) pretreatment with the caspase inhibitor (10 mg/kg) z-VAD-fink (intraperitoneally, 15 min before challenge). Survit was recorded over a period of 2 months...

Electron microscopic observations have shown that the cells of isolated gastrula ectoderm after some days in culture develop in their periphery a zone which contains vacuoles and in some cells the basal bodies of cilia. These are the same structures as found in epidermis. They are not found in the ectoderm, which was induced by the vegetalising factor. Obviously gastrula ectoderm is already determined to special pathways during differentiation, but its developmental fate can still be changed. In ectoderm treated with actinomycin D the vacuolar zone is retarded in its development (Grunz, 1973). A more general problem is raised by these experiments. Obviously, the induction of the ectoderm leads not only to an acquisition of new properties but also to a loss of properties which would have been expressed in the uninduced ectoderm. 

An increase in glucose utilization and in the biosynthesis of lipids, proteins, and RNA has been observed in ganglia which were treated with the factor. A rise of RNA synthesis precedes the increase of protein synthesis. Actinomycin D abolishes the effect of nerve growth factor on protein synthesis (Levi-Montalcini, 1967). 

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