Abstract
A downshift in temperature or exposure of cells to certain inhibitors of translation has been shown to induce the synthesis of cold shock proteins in Escherichia coli. We characterized the induction of the major cold shock protein (CS7.4, the product of the cspA gene) of E. coli in response to a shift from 37 to 15 degrees C and in response to the addition of chloramphenicol at 15 degrees C. A pulse-labeling assay and primer extension experiments indicated that the cold shock treatment resulted in a transient increase in the level of the cspA transcript and a transient induction of CS7.4, while the addition of chloramphenicol resulted in a constitutive increase in the level of cspA transcript and constitutive production of CS7.4. The addition of rifamycin immediately following the temperature downshift or along with the addition of chloramphenicol repressed the transcription of cspA as well as the induced production of CS7.4. Furthermore, changes in the cspA mRNA level were coincident with changes in CS7.4 synthesis. These results indicate that the expression of cspA induced by cold shock and chloramphenicol is at the level of transcription but not at the level of translation. Measurement of the half-life revealed that the cspA mRNA induced by chloramphenicol was more stable than that induced by cold shock.