NusA-dependent Transcription Termination Prevents Global Misregulation of Gene Expression

Canonical bacterial intrinsic terminators do not require additional factors for efficient transcription termination, although the general transcription elongation factor NusA was known to increase the termination efficiency slightly in vitro. We found that the effect of NusA varies widely among different terminators and identified a subclass of weak non-canonical terminators that largely depend on NusA for recognition by RNA polymerase. Using genome-wide 3' end-mapping on an engineered Bacillus subtilis NusA depletion strain, we identified >2000 intrinsic terminators, hundreds of which are NusA-dependent. Our in vitro and in vivo characterization showed that terminators with weak RNA hairpins and distal U-tract interruptions tend to be NusA-dependent. Our observations indicate that the lethality associated with deletion of nusA is caused by global readthrough of NusA-dependent terminators, resulting in misregulation of physiologically important downstream genes. We also show that nusA expression is autoregulated by a transcription attenuation mechanism that is mediated by NusA-dependent termination. Overall design: 3' end-mapping and mRNA profiling of stationary phase B. subtilis NusA-depletion (PLBS802) strain in NusA expressing and depleted conditions, 6 replicates each.