NusA interaction with the α subunit of E. coli RNA polymerase is via the UP element site and releases autoinhibition.

Elongating Escherichia coli RNAP is modulated by NusA protein. The C-terminal domain (CTD) of the RNAP α subunit (αCTD) interacts with the acidic CTD 2 (AR2) of NusA, releasing the autoinhibitory blockade of the NusA S1-KH1-KH2 motif and allowing NusA to bind nascent nut spacer RNA. We determined the solution conformation of the AR2:αCTD complex.