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The pyrrol[1,4]benzodiazepine antibiotics anthramycin, tomaymycin, sibiromycin, and neothramycins A and B are potent antitumor agents that bind to DNA in a unique manner, resulting in some unusual biological consequences. This paper describes results on which the points of covalent linkage between the drugs (carbinolamine carbon atom) and DNA (N-2 of guanine) are deduced, as well as Corey-Pauling-Koltun (CPK) models for the various drug-DNA adducts. Predictions based upon these CPK models have been tested, and the results are reported in this paper. These tested experimental predictions include (1) instability of the drug-DNA adducts to denaturation of DNA, (2) saturation binding limits, (3) effect of drug binding on the structure of DNA, (4) lack of unwinding and in vitro strand breakage of closed-circular supercoiled simian virus 40 (SV-40) DNA, (5) sensitivity of the secondary structure of DNA to drug binding, (6) hydrodynamic properties of the drug-DNA adducts, (7) hydrogen bonding of the 9-phenolic proton in anthramycin to DNA, (8) structure-activity relationships, and (9) biological consequences of DNA damage, including cumulative damage and slow excision repair, double-strain breaks in DNA in repair-proficient cells, and the selective inhibition of H-strand DNA synthesis in mitochondria. The results are completely in accord with our postulated space-filling models.

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A protein fraction from B. subtilis infected with phage SP01 (fraction LGG) stimulates the activity of RNA polymerase (EC 2.7.7.6; nucleosidetriphosphate:RNA nucleotidyltransferase) core from uninfected bacteria. Fraction LGG contains a protein (P-28, molecular weight 28,000) that is labeled after phage infection and binds tightly to RNA polymerase core at a relatively high ionic strength. B. subtilis RNA polymerase core with bound P-28 has the transcription specificity of the previously purified, phage-modified B-P RNA polymerase; the latter contains two subunits, v-28 and v-13 (molecular weights 28,000 and 13,000, respectively) that are synthesized after phage infection. Both enzymes transcribe SP01 DNA preferentially and direct the asymmetric synthesis of viral middle RNA. P-28, like v-28, binds more tightly to B. subtilis RNA polymerase core than the B. subtilis initiation factor, sigma, at higher ionic strength. We propose that P-28 and v-28 are the same protein. P-28 and, by implication, v-28 suffice to endow the bacterial RNA polymerase core with a novel transcription specificity.

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