The effect of aurintricarboxylic acid on RNA polymerase from rat liver.

The effect of the dye aurintricarboxylic acid (ATA) on RNA polymerases [EC 2.7.7.

Effect of stringent and relaxed control on transcription of the tryptophan operon from the ptrp promoter and the PL promoter in trp phage.

Tryptophan (trp) mRNA synthesis from the authentic trp promoter (Ptrp) is apparently arrested upon translation blockage, while trp mRNA synthesis as a result of read-through from the Pl promoter of the N gene in trp phage is not so affected. When translation is blocked at a nonpermissive temperature in the temperature-sensitive mutants of Escherichia coli rel carrying altered ribosomal elongation factors G (strain CP78G) and Ts (strain HAK88), CP78G and HAK88 show relaxed and stringent phenotypes respectively in control of RNA synthesis. Under conditions causing translation blockage in both mutants, Pl-promoted synthesis of trp mRNA is not depressed while Ptrp-promoted synthesis of trp mRNA is blocked.

Effect of l-asparaginase and asparagine deprivation on RNA metabolism in mouse leukemia L 5178Y cells in suspension culture.

We analyzed the effect of asparagine starvation and L-asparaginase on RNA metabolism of mouse leukemia cell lines L5178Y, whose growth is dependent on the presence of asparagine, and L5178Y-R, whose growth is independent of the presence of asparagine. The deprivation of asparagine from the medium inhibited cellular protein synthesis by 30 to 40% of the control value in L5178Y cells, but not in L5178Y-R cells, whereas L-asparaginase inhibited synthesis by more than 80% in both L5178Y and L5178Y-R cells. The decrease in protein synthesis caused by asparagine starvation in L5178Y cells was accompanied by a decrease in ribosomal RNA synthesis.

Initial trp operon sequence in Escherichia coli is transcribed without coupling to translation.

The transcription of the "leader" region (Bronson et al., 1973) of the trp operon in Escherichia coli was studied in normal mutants which delete most of the operator-distal region of the operon [a deletion strain (trp OAEG) retaining only about one third of the "leader" region and two deletion strains (trpOAE14 and trpOAE2) retaining the whole "leader" region and an initial portion of the trpE], as well as in a strain with an intact trp operon, but with a temperature-sensitive lesion in ribosomal protein factor EFTs (strain HAK88). In these deletion mutants, mRNA molecules corresponding to the "leader" region were detected as most of the trp-specific mRNA.

Potentiation of cytostatic effect of sulfur- or chlorine-containing purines and related ribonucleosides by amphotericin-B on cultured mouse leukemia cells.

Synergistic effects of sulfur-containing purines and related ribonucleosides (6-thioinosine, 6-thioguanine, 6-thiocyanatopurine, 6-methylthioinosine, 6-thiocyanatoguanine, 6-thiocyanatoguanosine, 6-phenacylthioinosine, 6-nitrobenzlythioinosine, 6-(p-chlorobenzyl)thioinosine, 6-(p-nitrobenzyl)thioguanosine, 6-benzylthioinosine, 6-ethylthioinosine, 6-benzylthioguanine, 6-benzylthiopurine, 6-methylthiopurine, and 6-thiocyanatoinosine) and chlorine-containing purine and its ribonucleoside, (6-chloropuine and 6-chloropurine riboside), in combination with the polyene antibiotic, Amphotericin-B, on cell survival and synthesis of DNA were examined in mouse leukemia L5178Y cells. 6-Methylthioinosine, 6-thiocyanatopurine, 6-thiocyanatoinsoine, 6-methylthiopurine, and 6-thiocyanatoguanine (or -guanosine) among sulfur-containing compounds were strongly potentiated by Amphotericin-B, and 6-chloropurine riboside, which is electronically analogous to methylthioinosine, was also enhanced by the polyene. Thiocyanoto or methylthio group at position 6 of the purine ring seems to be important for the polyene-mediated potentiation.

Synthesis and degradation of early mRNA in lambda phage.

Using two different Escherichia coli mutants defective in elongation factors EFG and EFTs required for peptide synthesis, lambda phage with or without a tof mutation was analysed for synthesis of early mRNA by DNA-RNA hybridization technique. (1) In CP78G carrying temperature-sensitive elongation factor G, shift-up to high temperature (41 degrees C) in the middle of phage infection did not affect early mRNA synthesis with lambdatof+ phage but did inhibit it with lambdatof- phage. (2) In HAK88 carrying temperature-sensitive elongation factor Ts, shift-up to 41 degrees C dropped total cellular RNA synthesis to below 10-20 percent of the control in the presence or absence of phage infection (stringent control).

Effect of cytochalasin-B on the transport of 5-fluorouracil in cultured mammalian cells.

Cytochalasin-B was found to inhibit the transport of uridine, but not leucine, in cultured fibroblastic mammalian cells. The inhibition of cellular protein synthesis by 5-fluorouracil is also lessened by the addition of Cytochalasin-B to the culture.

Potentiation of 5-fluorouracil, chromomycin A3, and bleomycin by amphotericin B or polymyxin B in transformed fibroblastic cells.

By using cultured, transformed fibroblastic cells, antitumor agents including cytosine arabinoside, thio-tepa, nitrogen mustard N-oxide, mitomycin C, chromomycin A3, 5-fluorouracil, daunomycin, vinblastine, vincristine, and bleomycin A2 were screened for the potentiation of their activity by amphotericin B or polymyxin B. Among them, the action of 5-fluorouracil and chromomycin A3 on ribonucleic acid synthesis was potentiated in their action by amphotericin B, not by polymyxin B. Bleomycin A2 was potentiated in its action on deoxyribonucleic acid and ribonucleic acid synthesis only by polymyxin B.

Temperature-sensitive mutation in regulation of ribonucleic acid synthesis in Escherichia coli.

An Escherichia coli mutant dependent on exogenous transfer ribonucleic acid (RNA) for bulk RNA formation at 42 C has been isolated, starting from a parental strain permeable to RNA. In the absence of added transfer RNA at the high temperature, protein synthesis stopped, and the strain formed little if any ribosomal RNA.

3',5'-cyclic adenosine monophosphate-requiring mutants of Escherichia coli.

Mutants that require exogenous 3',5'-cyclic adenosine monophosphate (cAMP) for exponential growth were isolated from strains deficient in adenyl cyclase. Studies of one strain showed that cAMP is not incorporated into macromolecules; instead, it seems to have a regulatory function, i.e.