LaserLaB Amsterdam and Department of Physics, VU University Amsterdam, De Boelelaan 1081, 1081HV Amsterdam, The Netherlands.
Weatherall Institute of Molecular Medicine, University of Oxford, John Radcliffe Hospital, Oxford, OX3 9DS, U. K.
Mol Cell. 2013 Sep 12;51(5):691-701. doi: 10.1016/j.molcel.2013.07.016. Epub 2013 Aug 22.
The Plk1-interacting checkpoint helicase (PICH) protein localizes to ultrafine anaphase bridges (UFBs) in mitosis alongside a complex of DNA repair proteins, including the Bloom's syndrome protein (BLM). However, very little is known about the function of PICH or how it is recruited to UFBs. Using a combination of microfluidics, fluorescence microscopy, and optical tweezers, we have defined the properties of PICH in an in vitro model of an anaphase bridge. We show that PICH binds with a remarkably high affinity to duplex DNA, resulting in ATP-dependent protein translocation and extension of the DNA. Most strikingly, the affinity of PICH for binding DNA increases with tension-induced DNA stretching, which mimics the effect of the mitotic spindle on a UFB. PICH binding also appears to diminish force-induced DNA melting. We propose a model in which PICH recognizes and stabilizes DNA under tension during anaphase, thereby facilitating the resolution of entangled sister chromatids.
Plk1 相互作用的检查点解旋酶（PICH）蛋白与包括布卢姆综合征蛋白（BLM）在内的一组 DNA 修复蛋白一起定位于有丝分裂中的超细后期桥（UFB）。然而，人们对 PICH 的功能或它如何被招募到 UFB 知之甚少。我们使用微流控技术、荧光显微镜和光镊的组合，在有丝分裂桥的体外模型中定义了 PICH 的特性。我们表明，PICH 与双链 DNA 具有极高的亲和力，导致 ATP 依赖性蛋白质易位和 DNA 的延伸。最引人注目的是，PICH 与 DNA 结合的亲和力随着张力诱导的 DNA 拉伸而增加，这模拟了有丝分裂纺锤体对 UFB 的作用。PICH 结合似乎也减少了力诱导的 DNA 熔解。我们提出了一个模型，其中 PICH 在后期识别和稳定张力下的 DNA，从而促进纠缠的姐妹染色单体的分辨率。
