A pH responsive RNA regulator

My talk will focus on the regulatory mechanism that induces expression of the alx locus. This locus, which encodes a putative transporter, was discovered in a screen for genes induced under extreme alkaline conditions in E. coli. The RNA region preceding the Alx ORF acts as a pH responsive RNA element (PRE), which upon exposure to high pH leads to an increase in Alx expression. Under normal growth conditions PRE forms a translationally inactive structure, but when exposed to high pH, a translationally active structure is formed, to produce Alx. Formation of the active structure occurs while transcription is in progress under alkaline conditions and involves pausing of RNA polymerase at two distinct sites. The characteristics of mutations affecting these pause sites will be discussed.