Following induction with IPTG, all strains showed increased hybridization above the 23S RNA band compared to the uninduced control with all three probes. The so-called 0 construct was described in reference (25) , and contains a slippery sequence and the UAA stop codon but no pseudoknot-like structure. In all strains, except the one with the 0 construct, there were a distinct band (Fl) representing the expected full-length transcript. The full-length transcript reached from transcription start to the stem-loop structure downstream of the 3 0 -end of the lacZ open reading frame ('hp' in Figure 4A ). This mRNA stem-loop structure has been shown to stabilize the lacZ transcript by reducing 3 0 -end exonucleolytic attacks (37) . The core plasmid contained no distinct transcription termination signal after the lacZ gene, and accordingly we found transcripts that exceeded far beyond the full-length Fl band ( Figure 4B-D) .