Stringent control of RNA synthesis in the absence of guanosine 5‘-diphosphate-3‘-diphosphate.

C.C Pao,B.T Dyess

doi:10.1016/s0021-9258(19)69769-3

Abstract

Severe curtailment of RNA synthesis and widespread readjustment of cellular activities, together with an increase of guanosine 5'-diphosphate-3'-diphosphate (ppGpp) have been demonstrated in Escherichia coli cells starved for amino acid or energy. The rates of growth and RNA synthesis are reduced by shifting the growth temperature from 40 degrees C to 20 degrees C. The intracellular pool of ppGpp diminishes under such conditions. Furthermore, the accumulation of ppGpp normally attainable by either amino acid- or energy-limitation can be totally blocked by a downshift of temperature imposed prior to the starvation. However, the synthesis of stable RNA is still stringently restricted under these conditions. Two other nucleotides were also effected. The intracellular level of phantom spot (Gallant, J., Shell, L., and Bittner, R. (1976) Cell 7, 75-84) decreased upon temperature fall. Guanosine 5'-diphosphate-3'-monophosphate, whose concentrations have been linked to stringent response and stable RNA synthesis, did not change by the simple temperature downshift, but increased following amino acid limitation even when a downshift of temperature was imposed before the starvation. These results suggest that ppGpp is not always needed for inhibition of stable RNA synthesis during stringent response, and that a compound such as guanosine 5'-diphosphate-3-monophosphate may be involved in the stringent regulation of stable RNA synthesis, at least under the temperature downshift conditions.

Highlights

Increase of guanosine 5’-diphosphate-3‘-diphosphate Possible regulatory effects of ppGpp have in the pasbteen have been demonstrated in Escherichiacoli investigated by many laboratories
Gent response and stable RNA synthesis, did notchange during the past several years we and other by the simple temperature downshift, but increased laboratories have noticed that under a number of conditions following amino acid limitation even when a downshift the intracellularpool size of ppGpp does noatlways correlate of temperature was imposed before the starvation. with therate of RNA synthesis [31,32,33,34,35,36,37,38]
Intracellular synthesis of RNA and ppGpp was compared in a wild type stringent strainof E. coli starved for amino acid or energy, as well as in relaxed cells starved for energy only (Fig. 1).RNA accumulation was reduced by more than a factor of 10 in reZA' cells upon either isoleucine deprivation or an energy source downshiftfrom glucose to succinate

Summary

RESULTS

Intracellular synthesis of RNA and ppGpp was compared in a wild type stringent strain (reZA+)of E. coli starved for amino acid or energy, as well as in relaxed (reZA) cells starved for energy only (Fig. 1).RNA accumulation was reduced by more than a factor of 10 in reZA' cells upon either isoleucine deprivation or an energy source downshiftfrom glucose to succinate. ATP pools in both strains were substantially smaller in cells though consistent, difference in the kinetics and final level of that were subjected to the 40 to 20°C temperature shift than ppGpp between the reZA' and reZA cells. This difference may in the steady state20°C grown cells (Table I). Its level practically reached its new 20°C basal level of approximately 20 pm0l/A7~n~m unit background within minutes after lowering the culture temperof cells It took even longer in reZA cells. The intracellular of Fig, 1also suggest that a decrease of ppGpp in response to concentrations of another guanosine nucleotide, ppGp, were not significantly influenced by the temperature. ppGp, which

TABLEI has been linked to stringent controland stableRNA synthesis

SLICE NUMBER

DISCUSSION