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. Author manuscript; available in PMC: 2013 Dec 1.
Published in final edited form as: Mol Microbiol. 2012 Oct 12;86(5):1167–1182. doi: 10.1111/mmi.12050

Figure 9. Proposed mechanism for the protection of espADB mRNA from degradation by RNase E.

Figure 9

The precursor sepL-espADB mRNA is processed near the end of sepL to generate espADB mRNA with a monophosphorylated 5' end. A translatable six-codon mini-ORF (black diamond) is located in the leader region upstream of the Shine-Dalgarno element for espA (SDA). A strong SD element (SD2) (striped square) enables mini-ORF translation (A). RNase E can degrade the transcript through a 5' end-dependent mechanism (grey solid arrow) or by direct interaction with AU-rich sequences in the leader region (grey dashed arrow) (B left and C). However, ribosome binding to SD2 acts as a barrier to RNase E by reducing the access of RNase E either to the monophosphorylated 5' end or to downstream cleavage sites (B right). RNase E cleavage is represented by scissors.