Characterization of DNA end-binding activities in higher plants

DNA double-strand-breaks (DSB) are the most severe lesion in cells exposing to ionizing radiation and many other stress environments. Repair of DNA DSB is therefore critical to cellular survival. In this work, we observed the double-stranded DNA end-binding (DEB) like activities in rice (Oryza sativa L. cv. TN5) suspension cells and hypocotyls from etiolated mung bean (Vigna radiata L. TN5) seedlings. Higher plant DEB-like protein binds primarily to linearized double-stranded DNA ends. Competition of unlabeled probe was examined in double-stranded DEB assay of cell extracts from rice and mung bean. DEB-like activities of higher plants did not depend on sequence and types of double-stranded DNA ends. Distinct electrophoretic mobility shift patterns and binding features further indicate that DEB-like factors from various sources might not share identical structure and function, and probably belong to different types of DEB proteins from higher plants. Our evidence suggests that DEB proteins are certainly ubiquitous in all organisms probably for repairing and processing double-stranded DNA breaks from formidable lethal lesion.