Figure 8.

Comparison of RNAPII recruitment to middle promoters in N4 and LUZ7. (left) Current model of transcription activation by N4 (49). In N4 there is a need for initial unwinding of the promoter region, thought to be performed by gp1. The resulting ssDNA region can then be bound by gp2, which recruits the phage-encoded RNAPII and thus activates its transcription. (right) Proposed model of RNAPII recruitment in LUZ7. Drc can already bind ssDNA regions that become available by torsional stress. Therefore it might not require an additional DNA-unwinding cofactor. Due to its double binding surface it can either bind one strand on each surface, or it binds a single strand with both surfaces. Additional Drc proteins are recruited through cooperative binding. At this stage, Drc might also be destabilizing the duplex and allow additional Drc to be bound. Drc then recruits RNAPII through direct protein-protein interaction. Potentially, this will lead to transcription activation similar to how it occurs in N4.