Biomaterial Database

DNA-dependent RNA polymerase from Pseudomonas BAL-31. II. Transcription of the allomorphic forms of bacteriophage PM2 DNA. 1975

S G Zimmer, and R L Millette

Transcription of the supercoiled form (I) and the relaxed circular form (II) of bacteriophage PM2 DNA was studied utilizing the DNA-dependent RNA polymerase from its host, Pseudomonas BAL-31. Transcription of both templates is continuous for up to 2 hr, but proceeds at a two-fold higher rate on I than on II. This difference is mainly due to a 2.2-fold higher rate of chain initiation on I. When rifampicin (Rif) is added ater 10 min of synthesis, (1) transcription of II ceases by 30 min with a maximum product length of 7000 nucleotides (number average) being produced; (2) transcription of I continues with little rate reduction and with the product reaching 16,000 nucleotides (number average) by 2 hr. Sucrose gradient analysis shows that the product of II achieves maximum size 20 min after Rif addition and sediments in three peaks of 24, 33, and 39 S (approximately one-third, two-thirds, and one genome lengths). The product of I has a heterogeneous distribution and grows continuously with a large fraction reacting greater than 3 genome lengths by 90 min. The same differences in synthesis kinetics, Rif inhibition, and product size distribution are observed when I and II are transcribed by Escherichia coli RNA polymerase. These experiments show that (i) PM2 form I DNA is transcribed mainly by a process of continuous chain elongation, with little chain termination occurring; (ii) PM2 form II is transcribed by a process of continuous chain initiation, elongation, and termination of yield discrete products. Thus, the tertiary structure of circular DNA influences chain termination by RNA polymerase.

UI	MeSH Term	Description	Entries
D007700	Kinetics	The rate dynamics in chemical or physical systems.
D011549	Pseudomonas	A genus of gram-negative, aerobic, rod-shaped bacteria widely distributed in nature. Some species are pathogenic for humans, animals, and plants.	Chryseomonas,Pseudomona,Flavimonas
D002499	Centrifugation, Density Gradient	Separation of particles according to density by employing a gradient of varying densities. At equilibrium each particle settles in the gradient at a point equal to its density. (McGraw-Hill Dictionary of Scientific and Technical Terms, 4th ed)	Centrifugations, Density Gradient,Density Gradient Centrifugation,Density Gradient Centrifugations,Gradient Centrifugation, Density,Gradient Centrifugations, Density
D004267	DNA Viruses	Viruses whose nucleic acid is DNA.	DNA Virus,Virus, DNA,Viruses, DNA
D004279	DNA, Viral	Deoxyribonucleic acid that makes up the genetic material of viruses.	Viral DNA
D001435	Bacteriophages	Viruses whose hosts are bacterial cells.	Phages,Bacteriophage,Phage
D012293	Rifampin	A semisynthetic antibiotic produced from Streptomyces mediterranei. It has a broad antibacterial spectrum, including activity against several forms of Mycobacterium. In susceptible organisms it inhibits DNA-dependent RNA polymerase activity by forming a stable complex with the enzyme. It thus suppresses the initiation of RNA synthesis. Rifampin is bactericidal, and acts on both intracellular and extracellular organisms. (From Gilman et al., Goodman and Gilman's The Pharmacological Basis of Therapeutics, 9th ed, p1160)	Rifampicin,Benemycin,Rifadin,Rimactan,Rimactane,Tubocin
D012321	DNA-Directed RNA Polymerases	Enzymes that catalyze DNA template-directed extension of the 3'-end of an RNA strand one nucleotide at a time. They can initiate a chain de novo. In eukaryotes, three forms of the enzyme have been distinguished on the basis of sensitivity to alpha-amanitin, and the type of RNA synthesized. (From Enzyme Nomenclature, 1992).	DNA-Dependent RNA Polymerases,RNA Polymerases,Transcriptases,DNA-Directed RNA Polymerase,RNA Polymerase,Transcriptase,DNA Dependent RNA Polymerases,DNA Directed RNA Polymerase,DNA Directed RNA Polymerases,Polymerase, DNA-Directed RNA,Polymerase, RNA,Polymerases, DNA-Dependent RNA,Polymerases, DNA-Directed RNA,Polymerases, RNA,RNA Polymerase, DNA-Directed,RNA Polymerases, DNA-Dependent,RNA Polymerases, DNA-Directed
D014158	Transcription, Genetic	The biosynthesis of RNA carried out on a template of DNA. The biosynthesis of DNA from an RNA template is called REVERSE TRANSCRIPTION.	Genetic Transcription