Enzymic synthesis of RNA from T7 DNA

Effect of actinomycin D on the transfer of ribonucleic acid from nucleus to cytoplasm in Lactobacillus acidophilus

After starvation for deoxyribosides, the deoxyribonucleic acid (DNA) of Lactobacillus acidophilus is restricted to a localized region of the cell. (3)H-uracil is first incorporated into such a restricted region but subsequently is found throughout the cell. This spread occurs despite the absence of protein synthesis and a major reduction in the rate of ribonucleic acid (RNA) synthesis. However, blocking RNA synthesis with actinomycin D restricts incorporation to a localized region of the cell. It is concluded that uracil is first incorporated into RNA in the bacterial nucleus from which it subsequently spreads through the cell. Actinomycin D could prevent this spread by preventing the completion of RNA molecules, which therefore do not dissociate from the DNA template.

Actinomycin Binding to DNA: Inability of a DNA Containing Guanine To Bind Actinomycin D

Polydeoxy (adenylyl-thymidylyl-cytidylyl)* polydeoxy(guanylyl-adenylyl-thymidylyl), a double-stranded DNA polmer of high molecular weight containing 33 percent guanine plus cytosine, binds little or no actinomycin D, as measured by five different techniques. In contrast, the sequence isomer of this DNA, polydeoxy (thymidylyl-adenylyl-cytidylyl)-polydeoxy(guanylyl-thymidylyl-adenylyl), does bind the antibiotic. Thus, the presence of guanine in a DNA is not a sufficient requisite for the binding of actinomycin D.