title: Transcriptional regulation of three double-stranded RNA segments of bacteriophage phi 6 in vitro.
abstract: Three double-stranded RNA segments of bacteriophage phi 6 (L, M, and S) were transcribed in vitro by a virion-associated RNA polymerase. Regulation of L transcription was distinct from regulation of M and S transcription. Transcription of the L segment, which codes for early proteins, required manganous ion and high concentrations of all four ribonucleoside triphosphates and was inhibited by polyamines such as spermine. Transcription of the M and S segments, which code for late proteins, required manganous or magnesium ion and relatively low concentrations of all ribonucleoside triphosphates except GTP and was enhanced by polyamines. Optimal conditions for L transcription were more stringent than those for M and S transcription. These two apparently different patterns produced in in vitro transcription presumably reflect the two distinct in vivo transcription patterns; i.e., (i) similar amounts of three single-stranded RNA species were transcribed from the three corresponding segments of double-stranded RNA (early pattern) and (ii) a much larger amount of single-stranded RNA species was transcribed from M and S segments than from the L segment (late pattern). The early transcription pattern may be changed into the late pattern by a change of environment, such as substrate concentration. This suggests that the different enzymatic properties under the different environmental conditions of the virion-associated transcriptase are responsible for the transcriptional regulation throughout the infection cycle of bacteriophage phi 6.
mesh_terms: D002413:Cations, Divalent; D002414:Cations, Monovalent; D012321:DNA-Directed RNA Polymerases / Q000235:genetics; D011073:Polyamines / Q000494:pharmacology; D011549:Pseudomonas; D012317:RNA Phages / Q000235:genetics*; D012330:RNA, Double-Stranded / Q000032:analysis*; D012367:RNA, Viral / Q000032:analysis*; D012265:Ribonucleotides / Q000235:genetics; D014158:Transcription, Genetic / Q000187:drug effects
chemical_list: D002413:Cations, Divalent; D002414:Cations, Monovalent; D011073:Polyamines; D012330:RNA, Double-Stranded; D012367:RNA, Viral; D012265:Ribonucleotides; D012321:DNA-Directed RNA Polymerases