Centre for Bacterial Cell Biology, Institute for Cell and Molecular Biosciences, Newcastle University, Baddiley-Clark Building, Richardson Road, Newcastle upon Tyne NE2 4AX, UK.
Nucleic Acids Res. 2013 Apr;41(8):4565-72. doi: 10.1093/nar/gkt116. Epub 2013 Feb 20.
The mechanisms of abortive synthesis and promoter escape during initiation of transcription are poorly understood. Here, we show that, after initiation of RNA synthesis, non-specific interaction of σ(70) region 1.2, present in all σ(70) family factors, with the non-template strand around position -4 relative to the transcription start site facilitates unwinding of the DNA duplex downstream of the transcription start site. This leads to stabilization of short RNA products and allows their extension, i.e. promoter escape. We show that this activity of σ(70) region 1.2 is assisted by the β-lobe domain, but does not involve the β'-rudder or the β'-switch-2, earlier proposed to participate in promoter escape. DNA sequence independence of this function of σ(70) region 1.2 suggests that it may be conserved in all σ(70) family factors. Our results indicate that the abortive nature of initial synthesis is caused, at least in part, by failure to open the downstream DNA by the β-lobe and σ region 1.2.
转录起始过程中，转录物合成的夭折机制和启动子逃避机制还未被完全理解。在这里，我们发现，在 RNA 合成起始之后，所有 σ(70)家族因子中都存在的 σ(70)区 1.2 与转录起始位点前-4 位的非模板链的非特异性相互作用有助于解开转录起始位点下游的 DNA 双链。这导致短 RNA 产物的稳定，并允许其延伸，即启动子逃避。我们发现，σ(70)区 1.2 的这种活性由β-叶域辅助，但不涉及β'-舵或β'-开关-2，这两个结构域之前被提议参与启动子逃避。σ(70)区 1.2 的这种功能的 DNA 序列独立性表明，它可能在所有 σ(70)家族因子中都保守。我们的结果表明，初始合成的夭折性质至少部分是由于 β-叶和 σ 区 1.2 未能打开下游 DNA 造成的。
