Transcription of the Filamentous Phage Genome

The F-specific filamentous coliphages, which include M13, f1, fd, ZJ/2, Ec9, AE2, HR, and δ A (for reviews, see Marvin and Hohn 1969; Denhardt 1975; Ray 1977), are composed of a single-stranded DNA molecule (m.w. ca. 2 × 10 6 ) in a capsid of about 2000 molecules of a protein (m.w. 5200) encoded by gene VIII, 2–3 molecules of a protein (m.w. ca. 52,000) specified by gene III, and a few molecules of a small protein, designated C protein (m.w. ca. 3000), the genetic origin of which is still unknown (Henry and Pratt 1969; Pratt et al. 1969; G. Simons et al., unpubl.; R. Webster and W. Konigsberg, pers. comm.). The DNA of the filamentous coliphages codes for at least nine polypeptides, and their corresponding genes have been ordered into a genetic map (Lyons and Zinder 1972; Seeburg and Schaller 1975; van den Hondel et al. 1975a,b; Vovis et al. 1975). Escherichia coli cells infected with these phages are neither lysed nor killed, but continue to grow and divide exponentially, although at a slower rate than uninfected cells, while extruding a few hundred new phage particles per cell generation. During this infection cycle, some polypeptides, such as the DNA-binding protein encoded by gene V and the major capsid protein encoded by gene VIII, are synthesized in much larger quantities than the other phage-encoded polypeptides (Henry and Pratt 1969; Lica and Ray 1976; Smits et al. 1978). These observations prompted us to initiate a study of the mechanisms which may be responsible...