TETHERING OF THE LARGE SUBUNITS OF ESCHERICHIA-COLI RNA-POLYMERASE

The rpoB and rpoC genes of eubacteria and archaea, coding, respectivel y, for the beta and beta'-like subunits of DNA-dependent RNA polymeras e, are organized in an operon with rpoB always preceding rpoC, Here, w e show that in Escherichia coil the two genes can be fused and that th e resulting 2751-amino acid beta::beta' fusion polypeptide assembles i nto functional RNA polymerase in vivo and in vitro, The results establ ish that the C terminus of the beta subunit and the N terminus of the beta' subunit are in close proximity to each other on the surface of t he assembled RNA polymerase during all phases of the transcription cyc le and also suggest that RNA polymerase assembly in vivo may occur co- translationally.