6S RNA regulates E-coli RNA polymerase activity

The E. coli 6S RNA was discovered more than three decades ago, yet its func tion has remained elusive. Here, we demonstrate that 6S RNA associates with RNA polymerase in a highly specific and efficient manner. UV crosslinking experiments revealed that 6S RNA directly contacts the sigma(70) and beta/b eta' subunits of RNA polymerase. 6S RNA accumulates as cells reach the stat ionary phase of growth and mediates growth phase-specific changes in RNA po lymerase. Stable association between sigma(70) and core RNA polymerase in e xtracts is only observed in the presence of 6S RNA. We show 6S RNA represse s expression from a sigma(70)-dependent promoter during stationary phase. O ur results suggest that the interaction of 6S RNA with RNA polymerase modul ates sigma(70)-holoenzyme activity.