Effect of ionic strength and temperature on the in vitro transcription of T 4 DNA

Cold-sensitive Pseudomonas RNA polymerase. II. Cold-promoted restriction of bacteriophage CB3 and the lack of host-dependent bacteriophage-specific RNA transcription

Cold-sensitive restriction of Pseudomonas phage CB3 by Pseudomonas aeruginosa strain PAT2 involves some aspect of CB3 specific RNA synthesis at 20 C. Experiments using chloramphenicol treatment and RNA-DNA hybridization establish that the amount of CB3 RNA present at 20 C is consistent with the known percentage of phage yielder cells at 20 C. Thus, it appears that nonyielder cells of PAT2 synthesize little or no phage-specific mRNA. Burgess technique extracted PAT2 RNA polymerase (RNAP) is cold sensitive when assayed in vitro with CB3 DNA at 20 C. However, it is not cold sensitive when either calf thymus or PAT2 DNA are the templates for transcription. Low ionic strength assay conditions eliminate the cold sensitivity of PAT2 RNAP. The effect of low ionic environments on transcription initiation along with the in vivo and in vitro suppression of cold sensitivity by host rifampin resistance suggests that the inability of CB3 to reproduce in PAT2 at 20 C is a cold-sensitive step in host RNAP initiation. Our modified RNAP extraction procedure for PAT2 and PAO1C also results in the recovery of cold-sensitive PAT2 RNAP with respect to CB3 DNA templates and points to basic enzymological differences between the two hosts. A model is presented for the unusual influence of temperature on the initiation process of both PAT2 and PAO1C on RNAP transcription.

DNA-directed synthesis in vitro of T4 phage-specific enzymes

The synthesis of deoxynucleotide kinase (EC 2.7.4.2) in vitro by a preparation consisting of T4 bacteriophage DNA and a cell-free extract of Escherichia coli has been reported. A study of the role of monovalent cations in the synthesis of this enzyme as well as alpha-glucosyl transferase (EC 2.4.1.2) shows that potassium ions are required for maximal enzyme production. Examination of the RNA-directed system indicates that potassium ions are more effective than ammonium ion in the translation of messenger RNA for the formation of the biologically active proteins studied. From a comparison of the magnitude of the effect of ions on both the DNA- and RNA-directed systems, we conclude that potassium ions may also have a marked stimulatory effect on transcription of the deoxynucleotide kinase gene of T4 DNA. The time required for messenger initiation and completion and the size distribution of messenger RNA formed in vitro were also examined.