Release of nascent trp mRNA from the operon DNA in chloramphenicol-treated cells of Escherichia coli.

When transcription of the E. coli trp operon is blocked as a result of inhibition of ribosomal activities by chloramphenicol, nascent trp mRNA but not RNA polymerase molecules seem to detach from the template DNA. The continued association of RNA polymerase with DNA is inferred because RNA synthesis resumes at or near the sites of transcription blockage after removal of the antibiotic. When E. coli cells infected with lambdatrp phage are incubated with chloramphenicol under the "Ptrp-promoted" conditions (Imamoto and Tani, 1972; Segawa and Imamoto, 1974), the trp mRNA molecules synthesized after removal of the antibiotic contain only promoter-distal information. They are usually small in size, in spite of the fact that chloramphenicol inhibition does not lead to the degradation of trp mRNA. On the other hand, PL-promoted trp transcription, which is non-polar and insensitive to chloramphenicol action, does not show such a premature release of nascent trp mRNA in chloramphenicol-treated cells.