Physics Department, Emory University, Atlanta, GA, USA.
Department of Molecular and Biomedical Science, University of Adelaide, Australia.
FEBS Lett. 2022 Aug;596(16):1994-2006. doi: 10.1002/1873-3468.14447. Epub 2022 Jul 22.
DNA can act as a scaffold for the cooperative binding of protein oligomers. For example, the phage 186 CI repressor forms a wheel of seven dimers wrapped in DNA with specific binding sites, while phage λ CI repressor dimers bind to two well-separated sets of operators, forming a DNA loop. Atomic force microscopy was used to measure transcription elongation by Escherichia coli RNA polymerase (RNAP) through these protein complexes. 186 CI, or λ CI, bound along unlooped DNA negligibly interfered with transcription by RNAP. Wrapped and looped topologies induced by these scaffolded, cooperatively bound repressor oligomers did not form significantly better roadblocks to transcription. Thus, despite binding with high affinity, these repressors are not effective roadblocks to transcription.
DNA 可以作为蛋白质寡聚体协同结合的支架。例如，噬菌体 186CI 阻遏物形成一个由七个二聚体组成的轮状结构，包裹在具有特定结合位点的 DNA 上，而噬菌体 λ CI 阻遏物二聚体结合到两个相隔较远的操纵子上，形成 DNA 环。原子力显微镜被用于测量大肠杆菌 RNA 聚合酶（RNAP）通过这些蛋白质复合物的转录延伸。186CI 或 λ CI 结合在非环化 DNA 上时，对 RNAP 的转录几乎没有干扰。由这些支架协同结合的阻遏物寡聚体诱导的包裹和环化拓扑结构并没有形成对转录更好的显著阻碍。因此，尽管这些阻遏物具有高亲和力结合，但它们并不是有效的转录阻碍物。
