2010年7月9日，北京生命科学研究所郭岩实验室在The Plant Cell杂志在线发表题为“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。该文报道了在拟南芥体内发现两个与哺乳动物CSA蛋白同源性较高的蛋白CSAat1A和CSAat1B，在植物体内形成CUL4-DDB1CSAat1A and B复合体，对UV造成的DNA损伤修复作出应答。
本研究通过正向遗传学方法，筛选到一个对UV-B敏感的突变体（csaat1a-3），克隆基因发现CSAat1A编码一个与哺乳动物中Cockayne Syndrome （CSA）同源的蛋白。拟南芥中还存在一个与CSAat1A高度同源的蛋白CSAat1B，完全缺失CSAat1A或CSAat1B的突变体表现出对UV-B和MMS （Methyl Methanesulfonate）敏感的表型。研究发现CSAat1A和CSAat1B通过转录偶联修复（TCR）方式对损伤的DNA进行修复，它们均能与CUL4 (CULLIN4)-DDB1A 在细胞核内形成复合物，CSAat1A和CSAat1B两个蛋白的WDxR motif对复合物的形成起着重要作用。另外，CSAat1A和CSAat1B能在细胞核内形成异源四聚体。该复合物的形成对两个蛋白行使功能至关重要。这些发现揭示CUL4-DDB1CSAat1A and B 代表一类新的通过促进底物的泛素化来应答DNA损伤修复的E3复合物。
博士研究生张彩果为本文的第一作者，论文作者还包括郭惠萍、张军、和兰州大学的郭光沁教授。郭岩博士为本文通讯作者。此项研究由科技部863计划资助。(生物谷Bioon.net)
生物谷推荐原文出处：
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.
