Identification of related genes in phages phi 80 and P22 whose products are inhibitory for phage growth in Escherichia coli IHF mutants.
Bacteriophage lambda grows in both IHF+ and IHF- host strains, but the lambdoid phage phi 80 and hybrid phage lambda (QSRrha+)80 fail to grow in IHF- host strains. We have identified a gene, rha, in the phi80 region of the lambda(QSRrha+)80 genome whose product, Rha, inhibits phage growth in an IHF- host. A search of the GenBank database identified a homolog of rha, ORF201, a previously identified gene in phage P22, which similarly inhibits phage growth in IHF- hosts. Both rha and ORF201 contain two possible translation start sites and two IHF binding site consensus sequences flanking the translation start sites. Mutations allowing lambda (QSRrha+)80 and P22 to grow in IHF- hosts map in rha and ORF201, respectively. We present evidence suggesting that, in an IHF+ host, lambda(QSRrha+)80 expresses Rha only late in infection but in an IHF- host the phage expresses Rha at low levels early in infection and at levels higher than those in an IHF+ host late in infection. We suspect that the deregulation of rha expression and, by analogy, ORF201 expression, is responsible for the failure of phi80, lambda(QSRrha+)80, and P22 to grow in IHF mutants.
Henthorn
K S
KS
Department of Human Genetics, University of Michigan, Ann Arbor 48109, USA.
Friedman
D I
DI
D000595:Amino Acid Sequence; D001426:Bacterial Proteins / Q000502:physiology; D017100:Bacteriophage P22 / Q000235:genetics*; D001483:Base Sequence; D003090:Coliphages / Q000235:genetics*; D017931:DNA Primers / Q000737:chemistry; D004926:Escherichia coli / Q000235:genetics; D015967:Gene Expression Regulation, Viral; D005814:Genes, Viral; D034982:Integration Host Factors; D008969:Molecular Sequence Data; D016415:Sequence Alignment; D017384:Sequence Deletion; D017386:Sequence Homology, Amino Acid; D014764:Viral Proteins / Q000235:genetics*; D015678:Viral Structural Proteins / Q000235:genetics
D001426:Bacterial Proteins; D017931:DNA Primers; D034982:Integration Host Factors; D014764:Viral Proteins; D015678:Viral Structural Proteins; C093814:rha protein, Bacteriophage phi-80