title: Bacteriophage P4 capsid-size determination and its relationship to P2 helper interference.
abstract: The sid (size determination) gene product of phage P4 is known to be involved in capsid-size determination. Moreover, the capsid-size determination function interferes with the lytic development of its helper P2, presumably because the helper genome is too large to be packaged into P4-size capsids. In order to study P4-specified helper interference, we cloned the sid gene for expression during phage infection. Even though gpSid restores the capsid-size determination function of a sid defective P4 mutant, we find that gpSid alone is not sufficient to establish full interference of helper P2 phage production. Complete helper interference requires some P4 function in addition to gpSid. Complementation tests show that none of the known P4 genes display this property. We propose that P4 encodes a yet-unidentified function that in concert with gpSid establishes full P2 helper interference at the level of capsid-size determination.
authors.affiliation: Laboratory of Microbial Gene Technology, NLVF, Norway. Oivindn@fagmed.uit.no
authors.forename: O
authors.initials: O
authors.lastname: Nilssen
authors.forename: C G
authors.initials: CG
authors.lastname: Fossdal
authors.forename: B V
authors.initials: BV
authors.lastname: Johansen
authors.forename: B H
authors.initials: BH
authors.lastname: Lindqvist
mesh_terms: D017901:Bacteriophage P2 / Q000235:genetics / Q000502:physiology*; D001483:Base Sequence; D002213:Capsid / Q000235:genetics / Q000502:physiology*; D036022:Capsid Proteins; D003090:Coliphages / Q000235:genetics / Q000502:physiology*; D017931:DNA Primers; D015870:Gene Expression; D006378:Helper Viruses / Q000235:genetics / Q000502:physiology*; D007700:Kinetics; D008969:Molecular Sequence Data; D010316:Particle Size; D012526:Satellite Viruses / Q000235:genetics / Q000502:physiology*; D014762:Viral Interference
chemical_list: D036022:Capsid Proteins; D017931:DNA Primers; C095129:Sid protein, Bacteriophage P4