Transcription in vitro of adenovirus-2 DNA by RNA polymerases class C purified from uninfected and adenovirus-infected HeLa cells

Specific termination of in vitro transcription by calf thymus RNA polymerase III

In vitro transcription of cleaved SV40 DNA with calf thymus RNA polymerase reveals a discrete transcript. The pattern of resistance to the inhibitor alpha-amanitin identifies the RNA as a product of RNA polymerase III transcription. The RNA is shown to initiate artificially near a DNA terminus created by cleavage and to terminate specifically near a cluster of 8 thymidine residues within the SV40 control region. Faithfully initiated transcripts cannot be detected using the calf thymus enzyme, supporting the idea that polymerase III termination can be accomplished by an initiation-deficient enzyme. Transcription of SV40 DNA in a HeLa cell lysate also leads to specific polymerase III transcription. When PvuII-cleaved DNA is the template, the same RNA is produced as with the calf thymus enzyme. At the lowered lysate concentration known to activate certain AluI-family transcripts, a collection of SV40 polymerase III transcripts is also produced. These do not depend on restriction cleavage of the DNA and thus arise from transcription of intact DNA.

Characteristics of the binding of RNA polymerase to template in mouse liver nuclei

In whole nuclei isolated from mouse liver, the reaction of free RNA polymerase with the artificial template, poly (dA-dT), is temperature dependent. At assay temperatures below 37 degrees C, the amount of free RNA polymerase (RNA polymerase not inhibited by actinomycin D) which can be measured is substantially reduced. However, if the nuclei are preincubated at 37 degrees C in the presence of template and then assayed at lower temperatures, substantial amounts of enzyme activity can be measured. The active complex (enzyme bound to template) is resistant to inactivation by heparin. This evidence is consistent with a two-stage model for binding of eukaryotic RNA polymerase to template similar to the binding of prokaryotic RNA polymerase to template.

In vitro transcription by wheat germ ribonucleic acid polymerase II: effects of heparin and role of template integrity

Double-stranded deoxyribonucleic acid (DNA) from bacteriophage lambda is a good template for wheat germ DNA-dependent ribonucleic acid (RNA) polymerase II. We delineated conditions for obtaining maximum polymerase activity using as template both the relatively intact DNA extracted from the the lambda phage and DNA into which single-strand nicks have been introduced by deoxyribonuclease (DNase) I digestion. The deliberate introduction of nicks produces a modest increase in transcription. The NaCl and MgCl2 optima are broader with the nicked template, so that higher concentrations of these salts are needed before polymerase activity begins to decline. Heparin inhibits initiation but not elongation by wheat germ polymerase. Polymerase can be protected against heparin inhibition by forming binary complexes with the template. The formation of these complexes is reduced at low temperature. The complexes, once formed, decay in the presence of heparin with a half-life of 10--20 min. The number of complexes is highly dependent on the degree of nicking of the template, suggesting that single-strand nicks are the predominant type of site where these heparin-resistant complexes are formed. Our data do not allow us to decide whether or not the presence of nicks plays as decisive a role in the absence of heparin.