Expression of Bacteriophage M13 DNA <em>in vivo</em>.

Hybridization studies have indicated that on the M13 genome there are located regions which are transcribed in vivo with a high as well as with a low frequency. The region with the highest transcriptional activity coincides with the region coding for the polypeptides which during the infection cycle are needed most abundantly (gene V and gene VIII protein). The hybridization studies furthermore have indicated that at least a number of the promoters previously detected in vitro are operative in the infected cell. In addition the experimental data are consistent with the presence of three transcription termination signals on the M13 genome. With the aid of analytical and preparative hybridization studies we have been able to establish that during the infection cycle at least eleven M13-specific RNA species are made which range in size from 280 to 2000 nucleotides. The six major RNA species (i.e. an 8-S RNA with 370 nucleotides, a 9-S with 420, three 11-S species with 760, 810 and 860 nucleotides and a 14- species with 1140 nucleotides) are encoded by the region with the highest transcriptional activity (located between the N-terminal end of gene X and the C-terminal end of gene VIII). Characterization of these RNA species with respect to their genetic origin, codogenic properties and nucleotide sequences has indicated that their synthesis is terminated at the previously detected rho-independent transcription termination signal T_0.25, which is located immediately after gene VIII. From the data obtained it furthermore could be deduced that the 5ʹ termini of these RNA .species are located as follows: for the 8-S RNA immediately in front of gene IX (promoter G_0.18), the 9-S RNA within or immediately distal to the 5ʹ end of gene VII, the three 11-S RNAs within the C-terminal end of gene X and the 14-S RNA immediately in front of gene X. Analyses of the 5ʹ ends of the major RNA chains synthesized in vivo have indicated that four (i.e. the 9-S and three 11-S species) out of the six RNA species are the result of processing of precursor molecules. For this processing the RNA processing enzymes RNase III, RNase E, and RNase P are not required. The meaning of these results, in terms of the mechanisms by which the expression of the M13 genome is regulated, is discussed. [ABSTRACT FROM AUTHOR]