Systematic nomenclature for the RNA polymerase genes of prokaryotes

Abstract

THE DNA-dependent RNA polymerase of Escherichia coli (EC 2.7.7.6) consists of at least four distinct polypeptide subunits; α, β, β′ and σ (ref. 1). Other subunits have been reported (for example, ω (ref. 1) and σ′ (ref. 2)), but their importance in transcription remains uncertain. Many prokaryotes are known to contain RNA polymerases of closely similar subunit composition, including a wide range of bacteria³ and a blue-green alga⁴. Until recently, only the structural gene for β had been identified in E. coli⁵. It is located^6–10 at 88.5 minutes on the recalibrated genetic map¹¹, and is characterised principally by mutations conferring resistance to specific drugs. The β-gene has thus acquired several synonyms derived from the mutant phenotypes, including rif (for resistance to rifampicin)⁶, stv (for strep-tovaricin)⁹, and stl (for streptolydigin)^10,12. More recently the structural gene for the β′ subunit has been characterised in E. coli; it is adjacent to the β gene¹³, and in the same operon^14–16. Finally, the gene coding for α has been located at 72 minutes^11,17–19. We now propose a systematic nomenclature for the RNA polymerase genes of E. coli, which could equally be applied to other prokaryotic organisms. We have consulted other workers in the field, whose comments have been assimilated into our proposal. The scheme, which is in line with the recommendations of Demerec et al.²⁰, is as follows.