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. 2011 Jun;75(2):286–300. doi: 10.1128/MMBR.00032-10

Fig. 4.

Fig. 4.

Mechanisms of transcription termination by bacterial asRNAs. (A) Organization of the Vibrio anguillarum iron transport-biosynthesis operon. The asRNA RNAβ induces transcription termination at a predicted stem-loop after the fatABCD part of the mRNA (89). (B) Schematic representation of the virA-rnaG-icsA (virG) locus of the Shigella flexneri pVIN plasmid and visualization of the proposed transcription termination mechanism (28). The 5′ region of the newly transcribed icsA message forms the stem-loop structure AH1 (1), and, without binding to RnaG, another stem-loop (AH2) is formed. This 5′ structure resembles an antiterminator structure (2a), and the full-length mRNA could be transcribed (3a). When RnaG is present, it forms a heteroduplex with the growing icsA message. This inhibits the formation of the antiterminator structure, and a terminator hairpin is formed (2b). Subsequently, transcription is attenuated, and a ∼100-nt abortion RNA is released (3b).