Editors' ChoiceMicrobiology

Spot 42 RNA Regulates Polycistronic Translation

Science's STKE  16 Jul 2002:
Vol. 2002, Issue 141, pp. tw257
DOI: 10.1126/stke.2002.141.tw257

The Escherichia coli galactose operon is regulated by the adenosine 3′,5′-monophosphate (cAMP) receptor protein (CRP) and is transcribed as a polycistronic message. However, the translation of the proteins encoded by the polycistronic message [UDP-galactose-4-epimerase (GalE), galactose-1-phosphate uridyl transferase (GalT), and galactokinase (GalK)] differs under different metabolic conditions, so-called "discoordinate expression." Decreased cAMP or glucose as a carbon source results in decreased amounts of GalK and GalT; whereas GalE is more abundant. Spot 42 RNA is transcribed from the spot forty-two (spf) gene, which is inhibited by cAMP through the CRP. Overexpression of spf inhibited synthesis of GalK, selectively, having little effect on the synthesis of other proteins from the galactose operon. In cells deficient for CRP, the expression of spf and GalK was reduced. This effect on GalK was abolished if the cells were also deficient for spf. Spot 42 RNA bound to the galK region of the polycistronic galactose operon message. Thus, Spot 42 RNA mediates the inhibition of GalK translation to produce discoordinate gene expression from a polycistronic RNA in response to changes in metabolic status in E. coli.

T. Møller, T. Franch, C. Udesen, K. Gerdes, P. Valentin-Hansen, Spot 42 RNA mediates discoordinate expression of the E. coli galactose operon. Genes Dev. 16, 1696-1706 (2002). [Abstract] [Full Text]

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