THE EXPRESSION OF RECOMBINANT GENES FROM BACTERIOPHAGE-LAMBDA STRONG PROMOTERS TRIGGERS THE SOS RESPONSE IN ESCHERICHIA-COLI

The production of several non-related heterologous proteins in recombi nant Escherichia coli cells promotes a significant transcription of re cA and sfiA SOS DNA repair genes. The activation of the SOS system occ urs when the expression of plasmid-encoded genes is directed by the st rong lambda lytic promoters, but not by IPTG-controlled promoters eith er at 37 or at 42 degrees C, and it is linked to an extensive degradat ion of the proteins after their synthesis. The triggering signal for t he SOS response could be an important arrest of cell DNA replication o bserved within the first hour after the induction of recombinant gene expression. The stimulation of this DNA repair system can partially ac count for the toxicity exhibited by recombinant proteins on actively p roducing E. coli cells. (C) 1998 John Wiley & Sons, Inc.