Translational efficiency of phi X174 lysis gene E is unaffected by upstream translation of the overlapping gene D reading frame

The lysis gene E of bacteriophage phi X174 is entirely embedded in gene D. Expression studies of genes D and E in Escherichia coli minicells and lysis times obtained in the presence or absence of D translation showed that the simultaneous expression of gene D does not affect protein E production. Thus, unlike other overlapping gene pairs, gene E expression is independent from the upstream translation of gene D. lacZ fusion studies and primer extension inhibition analysis (toeprinting) revealed an intrinsically weak E ribosome-binding site, which seems to be the major factor determining the low expression rate of the gene and thus proper scheduling of cell lysis.