Antisense RNA in Gene Regulation

All the regulators of gene expression that we have considered so far have been proteins. Several examples of RNA regulators have also been discovered. These small RNA molecules are complementary to particular sequences on mRNAs and are called antisense RNA. They control gene expression by binding to sequences on mRNA and inhibiting translation.

Translational control by antisense RNA is seen in the regulation of the ompF gene of E. coli (< Figure 16.17a). Two E. coli genes, ompF and ompC, produce outer-membrane proteins that function as diffusion pores, allowing bacteria to adapt to external osmolarities (the tendency of water to move across a membrane owing to different ion concentrations). Under most conditions, both the ompF and the ompC genes are transcribed and translated. When the osmolarity of the medium increases, a regulator gene named micF—for

Low osmolarity mRNA

When extracellular osmolarity is low,.

ompFgene

High osmolarity micF gene

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