Differential Effects Of Actinomycin Research Articles

Changes in nuclear localization of An3, a RNA helicase, during oogenesis and embryogenesis in Xenopus laevis.

The immunolocalization of An3 protein, an ATP-dependent RNA helicase and a member of the DEAD box family, was compared with the localization of fibrillarin, a protein essential for rRNA processing, and snRNPs, which are involved in mRNA splicing reactions, during oogenesis and embryogenesis in Xenopus laevis. Although An3 protein was detected in the cytoplasm of all stages of oocytes, in most stages An3 protein was also present in the nucleus. Prior to stage I An3 protein was uniformly dispersed throughout the entire germinal vesicle; from stages I to V it was in nucleoli. By stage VI nucleolar labeling with anti-An3 disappeared and the protein was no longer present within nuclei. An3 reactivity was also present throughout the nuclei of follicle cells surrounding prestage I to stage VI oocytes. Both cytoplasmic and nuclear An3 staining were present in cells of stages 8 to 35 embryos; however, nuclear staining was punctate and uniformly distributed throughout the nucleoplasm. Fibrillarin was diffusely distributed throughout the entire germinal vesicle prior to stage I, localized exclusively to nucleoli of oocytes between stages I and VI and in nucleoli of stages 12 and 35 embryonic cells. Reactivity for snRNPs (anti-Sm) in germinal vesicles of prestage I oocytes was diffuse, and similar to the distribution of An3 and fibrillarin; in later stage oocytes anti-Sm staining was restricted to a population of granules, much fewer in number and more heterogeneous in size than nucleoli. Anti-Sm activity was apparent in nuclei of embryonic cells of stages 8 to 35 embryos. Although colocalization of the Sm epitope and An3 was not observed in developing oocytes and in embryonic cells, Sm reactive material was frequently found in close association with An3-positive nucleoli (oocytes) and nuclear deposits (embryonic cells). In stage IV and V oocytes treated with actinomycin D (4 micrograms/ml) to inhibit rRNA synthesis, nucleoli, which continued to possess fibrillarin, lacked An3; staining of follicle cell nuclei for An3 was unchanged. Treatment with 200 micrograms/ml actinomycin D to block mRNA synthesis, inhibited An3 but not fibrillarin staining in nuclei of prestage I oocytes and follicle cells. The changing patterns of An3 reactivity and the differential effects of actinomycin D on such localizations observed here are consistent with a role for An3 in the processing/production of RNA.

Differential Effects of Actinomycin D and Cordycepin in Lettuce Seed Germination and RNA Synthesis

Intact lettuce seed germination was inhibited by cordycepin but not by actinomycin D; however, when seeds were clipped at the cotyledonary end, actinomycin D partially inhibited germination. Uptake studies with intact seeds using (3)H-actinomycin D showed that it was unable to reach the embryo prior to radical protrusion. (3)H-Cordycepin uptake studies using intact seeds showed that cordycepin was able to reach the embryo during the first 3 hours of incubation and at subsequent times. The pericarp and endosperm offered resistance to penetration of cordycepin into the embryo. In contrast to actinomycin D, cordycepin markedly inhibited (3)H-uridine incorporation into RNA of intact seeds during the first 10 and 12 hours of incubation. About 60% of (3)H-adenosine incorporation into poly A-RNA was inhibited by cordycepin during 12 hours of incubation, whereas actinomycin D had little effect. RNA synthesis appears to be essential for seed germination.

Differential effect of actinomycin D on amino acid incorporation by microsomal components of the housefly Musca domestica

Sucrose density gradient centrifugation was used to fractionate the microsomes from the housefly Musca domestica into two components, the free ribosomes and the membranes. The effect of actinomycin D (AM) on the in vivo incorporation of leucine into these fractions was studied. Actinomycin D rapidly inhibited RNA synthesis which however, did not result in a rapid inhibition of incorporation of leucine into the free ribosomes. The half-decay time of this inhibition was about 5 h suggesting a relatively stable m RNA. Under identical conditions the incorporation of leucine into the proteins of the membranes was stimulated about two-fold within 2 h after treatment. This enhanced rate of incorporation could be maintained for at least 4 h by a subsequent injection of actinomycin otherwise it rapidly fell off to normal levels. Puromycin completely prevented this stimulation by actinomycin. It is suggested that this enhanced incorporation is due to de-repression of membrane activity as a result of preferential inhibition of synthesis of mRNA for the repressor protein.

Differential effect of Actinomycin D on plant-virus multiplication

Differential effect of Actinomycin D on plant-virus multiplication

Differential effects of actinomycin D and puromycin on the release of interferon induced by double stranded RNA.

THE induction of interferon production with synthetic double stranded RNA1 is suppressed by actinomycin D2,3. Finkelstein et al.4, however, reported that considerably higher concentrations of actinomycin D were required for the suppression of interferon production induced by double stranded RNA than for the inhibition of viral-induced interferon synthesis. Moreover, the release of interferon after treatment with double stranded RNA in the intact organism5 or in cell cultures4 was not suppressed by inhibitors of protein synthesis, while viral-induced interferon synthesis was inhibited in the same conditions.

Differential effects of actinomycin D on cell division and light-induced chloroplast development in Euglena

Light-induced chloroplast development in resting cells of Euglena gracilis var. bacillaris, as judged from measurements of the kinetics of chlorophyll formation, photosynthetic carbon dioxide fixation, and observations in the fluorescence microscope, is progressively inhibited by increasing concentrations of actinomycin D (AM D) with 80% inhibition occurring at about 45 μg/ml. The extent of inhibition finally achieved is also related to the length of time that the cells have been exposed to AM D. In contrast to the high concentration of AM D necessary to produce a significant inhibition of chloroplast development, cell division is extremely sensitive and is completely inhibited at concentrations of 7–10 μg/ml. At all concentrations of AM D employed, colony formation from treated cells was impaired to a large extent, but all colonies observed were green, indicating that AM D does not selectively block chloroplast replication. The effects of AM D, in general, were potentiated by carrying out chloroplast development and colony formation in red light, which presumably prevents photodestruction of the inhibitor. The extensive labeling of cellular RNA with 32PO 4 3− that normally accompanies light-light-induced chloroplast development is almost completely inhibited by 45 μg/ml of AM D, as is the minimal labeling of the RNA of the dark controls. The differential sensitivities of chloroplast development, chloroplast replication, and cell division to AM D is discussed with reference to its known effect as an inhibitor of DNA-dependent RNA synthesis.

Differential effects of actinomycin D on nucleic acid and protein synthesis in rat liver

Levels of actinomycin D which block up to 90% of RNA synthesis in liver inhibit protein synthesis by 40%. A 50% inhibition of RNA synthesis is accompanied by less than a 5% inhibition of protein synthesis. These results indicate that the effects of actinomycin D on protein synthesis may be only partially related to the antibiotic effects on RNA synthesis.

Immunologically determined and competent cells are affected differentially by actinomycin D

A differential effect of actinomycin D on the capacity of mouse peritoneal fluid cells to form antibody after cell transfer has been found. Actinomycin treatment in vitro during transfer inhibited the delayed response toward a first antigen, administered before transfer, while the competence of cells to respond to a second antigen, given aftertransfer, was not affected.

IMMUNOLOGICALLY DETERMINED AND COMPETENT CELLS ARE AFFECTED DIFFERENTIALLY BY ACTINOMYCIN D.

A differential effect of actinomycin D on the capacity of mouse peritoneal fluid cells to form antibody after cell transfer has been found. Actinomycin treatment in vitro during transfer inhibited the delayed response toward a first antigen, administered before transfer, while the competence of cells to respond to a second antigen, given aftertransfer, was not affected.

The differential effect of actinomycin D on the biosynthesis of enzymes in Bacillus subtilis and Bacillus cereus☆

Relatively low concentrations (0.05–0.1 μg/ml) of actinomycin D cause marked inhibition of the growth of Bacillus cereus and Bacillus subtilis and have a striking differential effect on enzyme production. In B. subtilis a concentration of the drug causing 30% inhibition of growth will almost abolish induction of α-glucosidase (α- d -glucoside glucohydrolase, EC 3.2.1.20) without affecting penicillinase (penicillin amidohydrolase, EC 3.5.2.6) induction. In B. cereus the sensitivity of the penicillinase-forming system to inhibition by actinomycin depends upon the state of inducibility and the stage of induction: in preinduced cultures of the inducible strain, the system is temporarily (up to 40 min) much more resistant than in cells induced simultaneously with addition of the drug; whereas in the constitutive mutant it is unaffected for nearly 2 h. Very low concentrations of actinomycin (0.01–0.025 μg/ml) may stimulate the rate of induced penicillinase formation in B. subtilis by up to 100%, but have much less effect, if any, on production of the enzyme in constitutive mutants. These findings are believed to lend some support to the messenger RNA hypothesis as applied to enzyme formation in these organisms and suggest that messenger RNA for penicillinase formation in B. cereus may be metabolically stable for up to 40 min. They also suggest the possibility that the differential effect of actinomycin (at concentrations insufficient to saturate the DNA of the cell) may be due to differences in its combining affinity for different genes.

The differential effect of actinomycin D on the biosynthesis of enzymes in Bacillus subtilis and Bacillus cereus

Relatively low concentrations (0.05–0.1 μg/ml) of actinomycin D cause marked inhibition of the growth of Bacillus cereus and Bacillus subtilis and have a striking differential effect on enzyme production. In B. subtilis a concentration of the drug causing 30% inhibition of growth will almost abolish induction of α-glucosidase (α- d-glucoside glucohydrolase, EC 3.2.1.20) without affecting penicillinase (penicillin amidohydrolase, EC 3.5.2.6) induction. In B. cereus the sensitivity of the penicillinase-forming system to inhibition by actinomycin depends upon the state of inducibility and the stage of induction: in preinduced cultures of the inducible strain, the system is temporarily (up to 40 min) much more resistant than in cells induced simultaneously with addition of the drug; whereas in the constitutive mutant it is unaffected for nearly 2 h. Very low concentrations of actinomycin (0.01–0.025 μg/ml) may stimulate the rate of induced penicillinase formation in B. subtilis by up to 100%, but have much less effect, if any, on production of the enzyme in constitutive mutants. These findings are believed to lend some support to the messenger RNA hypothesis as applied to enzyme formation in these organisms and suggest that messenger RNA for penicillinase formation in B. cereus may be metabolically stable for up to 40 min. They also suggest the possibility that the differential effect of actinomycin (at concentrations insufficient to saturate the DNA of the cell) may be due to differences in its combining affinity for different genes.

The differential effect of actinomycin D on the biosynthesis of enzymes in Bacillus subtilis and Bacillus cereus

Relatively low concentrations (0.05–0.1 μg/ml) of actinomycin D cause marked inhibition of the growth of Bacillus cereus and Bacillus subtilis and have a striking differential effect on enzyme production. In B. subtilis a concentration of the drug causing 30% inhibition of growth will almost abolish induction of α-glucosidase (α-d-glucoside glucohydrolase, EC 3.2.1.20) without affecting penicillinase (penicillin amidohydrolase, EC 3.5.2.6) induction. In B. cereus the sensitivity of the penicillinase-forming system to inhibition by actinomycin depends upon the state of inducibility and the stage of induction: in preinduced cultures of the inducible strain, the system is temporarily (up to 40 min) much more resistant than in cells induced simultaneously with addition of the drug; whereas in the constitutive mutant it is unaffected for nearly 2 h. Very low concentrations of actinomycin (0.01–0.025 μg/ml) may stimulate the rate of induced penicillinase formation in B. subtilis by up to 100%, but have much less effect, if any, on production of the enzyme in constitutive mutants. These findings are believed to lend some support to the messenger RNA hypothesis as applied to enzyme formation in these organisms and suggest that messenger RNA for penicillinase formation in B. cereus may be metabolically stable for up to 40 min. They also suggest the possibility that the differential effect of actinomycin (at concentrations insufficient to saturate the DNA of the cell) may be due to differences in its combining affinity for different genes.