2010年7月9日，北京生命科學(xué)研究所郭巖實驗室在The Plant Cell雜志在線發(fā)表題為“Arabidopsis Cockayne Syndrome A-Like Proteins 1A and 1B Form a Complex with CULLIN4 and Damage DNA Binding Protein 1A and Regulate the Response to UV Irradiation”的文章,。該文報道了在擬南芥體內(nèi)發(fā)現(xiàn)兩個與哺乳動物CSA蛋白同源性較高的蛋白CSAat1A和CSAat1B,，在植物體內(nèi)形成CUL4-DDB1CSAat1A and B復(fù)合體，對UV造成的DNA損傷修復(fù)作出應(yīng)答,。
本研究通過正向遺傳學(xué)方法,，篩選到一個對UV-B敏感的突變體（csaat1a-3），克隆基因發(fā)現(xiàn)CSAat1A編碼一個與哺乳動物中Cockayne Syndrome （CSA）同源的蛋白,。擬南芥中還存在一個與CSAat1A高度同源的蛋白CSAat1B,，完全缺失CSAat1A或CSAat1B的突變體表現(xiàn)出對UV-B和MMS （Methyl Methanesulfonate）敏感的表型。研究發(fā)現(xiàn)CSAat1A和CSAat1B通過轉(zhuǎn)錄偶聯(lián)修復(fù)（TCR）方式對損傷的DNA進(jìn)行修復(fù),，它們均能與CUL4 (CULLIN4)-DDB1A 在細(xì)胞核內(nèi)形成復(fù)合物,，CSAat1A和CSAat1B兩個蛋白的WDxR motif對復(fù)合物的形成起著重要作用。另外,，CSAat1A和CSAat1B能在細(xì)胞核內(nèi)形成異源四聚體,。該復(fù)合物的形成對兩個蛋白行使功能至關(guān)重要。這些發(fā)現(xiàn)揭示CUL4-DDB1CSAat1A and B 代表一類新的通過促進(jìn)底物的泛素化來應(yīng)答DNA損傷修復(fù)的E3復(fù)合物,。
博士研究生張彩果為本文的第一作者,，論文作者還包括郭惠萍,、張軍、和蘭州大學(xué)的郭光沁教授,。郭巖博士為本文通訊作者,。此項研究由科技部863計劃資助。(生物谷Bioon.net)
生物谷推薦原文出處：
The Plant Cell doi：10.1105/tpc.110.073973
Arabidopsis Cockayne Syndrome A-Like Proteins 1A and 1B Form a Complex with CULLIN4 and Damage DNA Binding Protein 1A and Regulate the Response to UV Irradiation
Caiguo Zhanga,b, Huiping Guoc, Jun Zhangb, Guangqin Guoa, Karen S. Schumakerd and Yan Guob,c,1
a Institute of Cell Biology, School of Life Sciences, Lanzhou University, Lanzhou 730000, China
b National Institute of Biological Sciences, Beijing 102206, China
c State Key Laboratory of Plant Physiology and Biochemistry, College of Biological Sciences, China Agricultural University, Beijing 100094, China
d Department of Plant Sciences, University of Arizona, Tucson, Arizona 85721
In plants, as in animals, DNA is constantly subject to chemical modification. UV-B irradiation is a major genotoxic agent and has significant effects on plant growth and development. Through forward genetic screening, we identified a UV-B–sensitive mutant (csaat1a-3) in Arabidopsis thaliana, in which expression of CSAat1A, encoding a Cockayne Syndrome A-like protein, is reduced due to insertion of a T-DNA in the promoter region. Arabidopsis lacking CSAat1A or its homolog CSAat1B is more sensitive to UV-B and the genotoxic drug methyl methanesulfonate and exhibits reduced transcription-coupled repair activity. Yeast two-hybrid analysis indicated that both CSAat1A and B interact with DDB1A (UV-Damage DNA Binding Protein1). Coimmunoprecipitation assays demonstrated that CSAat1A and B associate with the CULLIN4 (CUL4)-DDB1A complex in Arabidopsis. A split-yellow fluorescent protein assay showed that this interaction occurs in the nucleus, consistent with the idea that the CUL4-DDB1A-CSA complex functions as a nuclear E3 ubiquitin ligase. CSAat1A and B formed heterotetramers in Arabidopsis. Taken together, our data suggest that the plant CUL4-DDB1ACSAat1A and B complex represents a unique mechanism to promote ubiquitination of substrates in response to DNA damage.
