| Summary: | 碩士 === 國立清華大學 === 生命科學系 === 87 === Ku protein was discovered in 1981 and identified as an autoantigen in the sera of certain patients with polymyositis scleroderma overlap syndrome. Ku is an abundant nuclear DNA-binding protein composed of two subunits of approximately 70 kDa and 8o kDa. Evidence showed that Ku interacts with free ends of double-stranded (ds) DNA without sequence specificity. Ku is presumably involved in pathways for DNA repair and recombination. We believe that all organisms may possess proteins to repair double strand breaks (dsbs) generated in their DNA by damaging agents. We attempted in this study to search possible existence of the Ku-like protein in the higher plant cells. We demonstrated activities of a Ku-like protein in rice suspension cells, a monocotyledon, and hypocotyls from etiolated mung bean, a dicotyledon. In addition, the exhibition of two DEB proteins, from rice and mung bean, which are unlike with respect to their response to Mg2+. Using the EMSA assay, Our results indicate that a new DNA-binding factor is a Ku-like protein that recognizes the ends of double-stranded DNA in the higher plant cells. Although these two DEB factors had a similar end-binding activity to Ku protein, but they are different from each other in some aspects.
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