Abstract
The Ku autoantigen is a complex composed of two subunits of Ku70 and Ku86. Ku protein is involved in DNA double-strand break repair and V(D)J recombination and is the DNA end-binding (DEB) component of the DNA-dependent protein kinase (DNA-PK). The kinase has been shown to phosphorylate proteins involved in repair, replication and transcription in vitro. Therefore, it is important to have a better understanding of the properties and functions of Ku. In this study, we investigated the transfer activity of Ku between two DNA molecules. By competitive EMSA assay and pulldown asssy, we found that Ku bound to one DNA molecule could transfer directly to another DNA molecule even these two DNA molecules do not have homologous ends under high salt, high magnesium condition (200 mM NaCl; 5 mM Mg2+). The preliminary result suggests that DNA ends can open easily to cause two fragments find matched bases and generate a complementary structure to help Ku transfer directly from one fragment to the others. Finally, we found the multimeric Ku on the DNA had different property in its transfer activity. In this situation, Ku could transfer to DNA without homologous ends under low or high salt conditions.