Molucular cloning and Characterization of Ku-like proteins in higher plants

• Main Authors: Pei-Feng Liu, 劉佩芬
• Other Authors: Rong-Long Pan
• Format: Others
• Language: zh-TW
• Published: 2001
• Online Access: http://ndltd.ncl.edu.tw/handle/61593481861047026537

碩士 === 國立清華大學 === 生命科學系 === 89 === Ku protein which composes of ~70- and ~80-kDa subunits was discovered originally as an autoantigen in the sera of patients with autoimmune diseases. Ku protein binds primarily to double-stranded DNA ends, especially blunt ends and 5’ or 3’overhang DNA. After binding to the DNA ends, Ku recruits the ~470 kDa DNA—dependent protein kinase catalytic subunit (DNA-PKcs) and becomes the regulatory subunit of DNA-PK that phosphorylates many proteins. Thus, Ku is responsible for the DNA-dependent activation of this enzyme. Ku and DNA-PKcs play important roles in repairing DNA double-stranded breaks under ionizing radiation as well as V(D)J recombination in immunoglobulin, T cell receptor and many important cellular functions, such as DNA replication, transcription regulation, and regulation of maintaining structure of telomeric termini; thus, Ku is a multifunctional DNA-binding protein. Homologues of Ku proteins have been found in many species, for instance, human, monkey, Xenopus, Drosophila, yeast, and rodents; albeit, but Ku from plant has not been found yet. Recent reports have proved that Ku or Ku-like proteins may exist in higher plants. In this study, we attempt to clone and characterize Ku-like proteins in higher plants. We used expressed sequence tags (ESTs), which are similar to human Ku proteins in soybean database, as probes to isolate cDNA from mung bean cDNA library. Our results indicated that the amino acid sequences of mung bean Ku-like proteins show certain degree of homology to human Ku proteins and Arabidopsis thaliana Ku-like proteins. We also used many computer programs to scrutinize their characteristics of amino acid sequence. According to these results, we could be sure that Ku or Ku-like proteins exist in higher plants.