The relationships among RNA synthesis, RNA polymerase synthesis and guanosine tetraphosphate levels in Escherichia coli during nutritional shift-up

Abstract

The relationships among the rate of RNA synthesis, RNA polymerase synthesis and activity, and guanosine tetraphosphate levels were investigated following nutritional shift-up in Escherichia coli. RNA synthesis continues at the preshift rate for 1.5 min after which an increase is observed that reaches a new steady-state rate at between 2 and 2.5 min. RNA polymerase activity measured in crude extracts increases immediately and by 10 min has increased 50%. RNA polymerase synthesis as measured by the synthesis of the β and β′ subunits lags for 2.5 min and then increases 75% by 10 min. Guanosine tetraphosphate levels decrease 50% by 3 min to levels characteristic of steady-state post-shift-up cells. The significance of these data to the regulation of RNA synthesis during shift-up is discussed.