ARTIFICIAL REGULATION OF GENE-EXPRESSION IN ESCHERICHIA-COLI BY RNASE-P

Plasmids encoding various external guide sequences (EGSs) were constru cted and inserted into Escherichia coli. In strains harboring the appr opriate plasmids, the expression of fully induced beta-galactosidase a nd alkaline phosphatase activity was reduced by more than 50%, while n o reduction in such activity was observed in strains with non-specific EgSs. The inhibition of gene expression was virtually abolished at re strictive temperatures in Strains that were temperature-sensitive for RNase P (EC 3.1.26.5). Northern blot analysis shelved that the steady- state copy number of EGS RNAs was several hundred per cell in vivo. A plasmid that contained a gene for M1 RNA covalently linked to a specif ic EGS reduced the level of expression of a suppressor tRNA that was e ncoded by a separate plasmid. Similar methods can be used to regulate gene expression in E. coil and to mimic the properties of cold-sensiti ve mutants.