Functional dissection of the plant-specific SBP-domain: Overlap of the DNA-binding and nuclear localization domains
Functional dissection of the plant-specific SBP-domain: Overlap of the DNA-binding and nuclear localization domains
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DOI：
10.1016/j.jmb.2005.07.013
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发表时间：
2005-09-23
影响因子：
5.6
通讯作者：
Huijser, P
中科院分区：
文献类型：
--
作者：
Birkenbihl, RP;Jach, G;Huijser, P
SBP结构域蛋白是植物特异性转录因子。它们都含有高度保守的76个氨基酸残基的SBP-结构域，显示出特异性结合金鱼草SQUA启动子和拟南芥AP 1启动子中的相关基序。这种DNA序列特异性结合的结构基础是由保守的半胱氨酸和组氨酸残基与两个锌离子配位形成的两个锌指状结构。所涉及的半胱氨酸残基的氨基酸交换揭示了每个Zn 2+配位结构对于DNA结合是必需的。通过随机靶位点选择研究，表明回文GTAC核心基序对于不同SBP结构域蛋白与优选的额外核苷酸的有效DNA结合是必需的。尽管它们在不同进化距离的植物中具有不同的功能和起源，但从单细胞藻类莱茵衣藻到苔藓小立碗藓和高等植物，DNA结合的模式是保守的。在SBP结构域的C末端，定位了推定的二分核定位信号，其与DNA结合结构域重叠，特别是与第二Zn 2+结合结构重叠。通过SPL3的免疫定位和植物细胞中的SBP-绿色荧光蛋白融合蛋白的瞬时表达，表明这种核定位信号是功能性的。天冬氨酸，这可能模拟磷酸化的核定位信号旁边的一个高度保守的丝氨酸交换，导致减少核输入（SPL8），而DNA结合在体外被完全废除。与此相反，交换丙氨酸增加核输入和左DNA结合完整。这表明，SBP结构域蛋白的功能也受到核输入和DNA结合水平上的翻译后修饰的调节。(c)2005爱思唯尔有限公司保留所有权利。
SBP-domain proteins are plant-specific putative transcription factors. They all contain the highly conserved 76 amino acid residue SBP-domain, shown to bind specifically to related motifs in the Antirrhinum majus SQUA promoter and the orthologous Arabidopsis thaliana AP1 promoter. The structural basis for this sequence-specific binding of DNA are two Zn-finger like structures formed by the coordination of two zinc ions by conserved cysteine and histidine residues. Amino acid exchanges of the cysteine residues involved revealed that each of the Zn2+-coordinating structures is essential for DNA binding. By random target-site selection studies, it is shown that the palindromic GTAC core motif is essential for efficient DNA binding with additional nucleotides preferred by different SBP-domain proteins. Despite their different functions and origin from plants at different evolutionary distances, the mode of DNA binding is conserved from the single-cell algae Chlamydomonas reinhardtii to the moss Physcomitrella patens and higher plants. At the C-terminal end of the SBP-domain, a putative bipartite nuclear localization signal is located, which overlaps with the DNA-binding domain, in particular with the second Zn2+-binding structure. By immunolocalization of SPL3 and transient expression of SBP-green fluorescent protein fusion proteins in plant cells, it is shown that this nuclear localization signal is functional. Exchange of a highly conserved serine next to the nuclear localization signal by aspartate, which may mimic phosphorylation, resulted in a decreased nuclear import (SPL8), while DNA binding in vitro was abolished completely. In contrast, exchange by alanine increased nuclear import and left DNA binding intact. This suggests that the function of SBP-domain proteins is also regulated by post-translational modification on the levels of nuclear import and DNA binding. (c) 2005 Elsevier Ltd. All rights reserved.