Complementation of T4 phage am mutations by hybrid phages λ-T4

Abstract

EcoRI fragments of the T4 cytosine-containing DNA (dC-DNA) were cloned in the lambda XIII vector phage carrying the only restriction site for EcoRI in the repressor gene of lambda. 38 genes of T4 were identified in the cloned fragments by means of marker rescue technique. All cloned early genes and some late genes of T4 were able to complement a corresponding am mutations of T4 phage when nonpermissive cells of E.coli were simultaneously infected with hybrid phages lambda-T4 and am mutants of T4. An average burst size for am mutants from su- cells (when complemented by corresponding hybrid phage) was 20-70 pfu for early genes and 1-3 to 20 pfu for late ones. When the extract of cells infected with hybrid phage lambda-T4-22 containing T4 genes 57, 1, 2, 64 was mixed with the extract of cells infected with T4N51 mutant, the complementation in vitro was observed. So, it was shown that normal product of late gene 2 is synthesized in the cells infected with hybrid phage lambda-T4-22 in the absence of positive regulators of transcription coded by early T4 genes.

Expression of T4 Early Genes 62, 44, 45 and 46 in the -T4 Recombinant Phage 806-17

“…By means of genetic complementation experiments, expression of the cloned gene group 46, 45, 44 and 62 has also been observed by two other groups (Vorozheikinia et al, 1980;Velten & Abelson, 1980). Since the complementation efficiencies of these genes are unaffected by the orientations of the T4 DNA fragment within the vector, Vorozheikinia et al (1980) further suggested that transcription of these genes may be initiated from the included T4 promoters.…”

“…Since the complementation efficiencies of these genes are unaffected by the orientations of the T4 DNA fragment within the vector, Vorozheikinia et al (1980) further suggested that transcription of these genes may be initiated from the included T4 promoters. Unfortunately, their experiments were conducted with non-lysogenic bacteria (for gene 45) and thus their experimental conditions do not completely rule out the possibility of expression of the cloned T4 genes from 2 promoters (Wilson & Murray, 1979;Murray et al, 1979).…”

“…Because T4 interferes with the development of phage 2 (Pearson & Snyder, 1980), a modification of the usual in vivo complementation test (Revel, 1981 ;Vorozheikinia et al, 1980) was used to check whether 2-T4 can synthesize functional T4 gene products (with their own promoter). Suppressor-free E. coli W3350 (~2~) cells were pre-infected with L-T4 recombinants at 37 °C to allow some expression prior to infection with T4 mutant phage.…”