The primary immunity determinant in modulating the lysogenic immunity of the filamentous bacteriophage cf.
Bacteriophage cf is the first single-stranded DNA phage that has been shown to set up a stable lysogenic state with its genome integrated into the host chromosome. From the isolation and characterization of a virulent mutant, cf-tv2, we report the first investigation into the mechanisms of the immunity established by the filamentous bacteriophage. The mutation in cf-tv2 enables the phage to produce plaques on lawns of cf lysogenic cells. The mutation was defined as a 49-nucleotide deletion located in a 0.59 kb NcoI/KpnI fragment of cf replicative form DNA. Two messages, cM1 and cM2, transcribed from the immunity region of wild-type cf but in opposite directions, were detected. In cf-tv2, the 49-nucleotide deletion abolishes cM2 transcription. The primer extension assay suggests a possible RNA-RNA interaction directed by base-pairing of the cM1 and cM2 RNAs. A frameshift mutation of the open reading frame ORF 165, encoded by cM2, resulted in a 10(5) plating efficiency on the cf lysogen. These observations suggest that both RNA-RNA interaction and repressor protein inhibition are involved in the mechanism of cf immunity. A model is proposed for the regulation of cf immunity.
Cheng
C M
CM
Institute of Molecular Biology and Institute of Botany, Academia Sinica, 115 Nankang, Taipei, Taiwan, Republic of China.
Wang
H J
HJ
Bau
H J
HJ
Kuo
T T
TT
D000595:Amino Acid Sequence; D001435:Bacteriophages / Q000472:pathogenicity* / Q000502:physiology*; D001483:Base Sequence; D003001:Cloning, Molecular; D008242:Lysogeny / Q000276:immunology*; D008969:Molecular Sequence Data; D009154:Mutation; D016366:Open Reading Frames; D012367:RNA, Viral / Q000235:genetics / Q000378:metabolism; D012097:Repressor Proteins / Q000235:genetics / Q000378:metabolism; D014158:Transcription, Genetic; D014774:Virulence / Q000276:immunology
D012367:RNA, Viral; D012097:Repressor Proteins