Transcription of Isometric Single-stranded DNA Phage

Abstract

Although the mechanisms involved are complex and varied, transcription in prokaryotic systems is characterized by the synthesis of RNA molecules of unique size and sequence that are complementary to definite regions of the particular genome. This selectivity of transcription (Chamberlin 1974) is determined by the interactions of specific sequences on the DNA template with the various components of the transcriptional apparatus. Study of the transcriptional selectivity for a particular system can proceed along several different lines: (a) characterization of the size and sequence of individual transcription units; (b) mapping of transcription units with respect to the genome; (c) determination of the regions of the genome, such as promoters and terminators, which act as transcriptional signals; (d) identification and characterization of the elements of the transcriptional machinery required for selectivity; (e) elucidation of the nature of the interactions between the transcriptional machinery and the transcriptional template. This review summarizes progress made along these lines in characterizing transcription by the isometric single-stranded (SS) DNA phages (IP). Almost all work relevant to this area has been carried out with the two very closely related phages, ϕ X174 and S13. Although there are differences in the nucleotide sequences of these two phages, as shown by analysis with restriction enzymes (Hayashi and Hayashi 1974; Godson and Roberts 1976), stability of heteroduplexes (Godson 1973; Compton and Sinsheimer 1977), and differences in the gel mobilities of some of the gene products (Jeng et al. 1970; Godson 1973), the basic features of transcription of ϕ X and S13 are virtually...