Wang J, Satoh M, Chou C H, Reeves W H
Department of Medicine, Thurston Arthritis Center, University of North Carolina, Chapel Hill 27599-7280.
FEBS Lett. 1994 Sep 5;351(2):219-24. doi: 10.1016/0014-5793(94)00863-9.
The Ku antigen consists of 70 and 80 kDa protein subunits (p70 and p80, respectively) that form the DNA binding component of a DNA-dependent protein kinase (DNA-PK). It is controversial whether the interaction of Ku with DNA is mediated by p70 alone or requires formation of p70/p80 dimers. In the present studies, the DNA binding properties of p70/p80 heterodimers and full-length human p70 expressed in the absence of p80 were investigated. The binding of free p70 and p70/p80 heterodimers to DNA showed similar sensitivity to high ionic strength buffers. Competitive DNA binding studies revealed that free p70, like the p70/p80 heterodimer, bound preferentially to linear double stranded DNA fragments, whereas tRNA and closed circular DNA molecules competed poorly with the radiolabeled linear DNA for binding to Ku. These studies suggest that free p70 and p70/p80 heterodimers have similar DNA binding properties, and that the interaction of Ku with DNA may depend primarily on the p70 subunit, possibly with implications for the assembly and function of DNA-PK.
Ku抗原由70 kDa和80 kDa的蛋白质亚基（分别为p70和p80）组成，它们构成了DNA依赖性蛋白激酶（DNA-PK）的DNA结合成分。Ku与DNA的相互作用是仅由p70介导还是需要形成p70/p80二聚体存在争议。在本研究中，对p70/p80异二聚体以及在无p80情况下表达的全长人p70的DNA结合特性进行了研究。游离的p70和p70/p80异二聚体与DNA的结合对高离子强度缓冲液表现出相似的敏感性。竞争性DNA结合研究表明，游离的p70与p70/p80异二聚体一样，优先结合线性双链DNA片段，而tRNA和闭环DNA分子与放射性标记的线性DNA竞争结合Ku的能力较差。这些研究表明，游离的p70和p70/p80异二聚体具有相似的DNA结合特性，并且Ku与DNA的相互作用可能主要取决于p70亚基，这可能对DNA-PK的组装和功能具有影响。
