T4 mutants lacking
polynucleotide kinase (pnk-) or
RNA ligase (rli-) do not grow on E. coli CTr5x. During the abortive
infections there accumulate host
tRNA fragments that match into two species severed 3' to the
anticodon. The CTr5x-specific fragments appear only transiently with wt phage, implicating the affected
enzymes in phosphoryl group rearrangement and religation [David et al. (1982) Virol. 123, 480]. In a search for the vulnerable host tRNAs and putative religation products,
tRNA ensembles from uninfected E. coli CTr5x or cells infected with various phage strains were fractionated and compared. A
tRNA species absent from rli- infected cells but present in uninfected cells or late in wt
infection was thus detected.
RNase T1 finger prints of this species, isolated before or after wt
infection, were compared with that of an in vitro ligated pair of CTr5x-specific fragments. The results indicated that this
tRNA is cleaved upon
infection and later on restored to it's original or to a very similar form, by
polynucleotide kinase and
RNA ligase reactions. It is suggested that depletion of such vulnerable host
tRNA species underlies the restriction of pnk- or rli- phage on E. coli CTr5x.