Song Young Hun, Yoo Cheol Min, Hong An Pio, Kim Seong Hee, Jeong Hee Jeong, Shin Su Young, Kim Hye Jin, Yun Dae-Jin, Lim Chae Oh, Bahk Jeong Dong, Lee Sang Yeol, Nagao Ron T, Key Joe L, Hong Jong Chan
Division of Applied Life Science (BK21 Program), Plant Molecular Biology and Biotechnology Research Center, Environmental Biotechnology Research Center, National Core Research Center, Gyeongsang National University, Jinju 660-701, Korea.
Plant Physiol. 2008 Apr;146(4):1862-77. doi: 10.1104/pp.107.113217. Epub 2008 Feb 20.
LONG HYPOCOTYL5 (HY5) is a bZIP (basic leucine zipper) transcription factor that activates photomorphogenesis and root development in Arabidopsis (Arabidopsis thaliana). Previously, STF1 (soybean [Glycine max] TGACG-motif binding factor 1), a homologous legume protein with a RING-finger motif and a bZIP domain, was reported in soybean. To investigate the role of STF1, the phenotypes of transgenic Arabidopsis plants overexpressing STF1 and HY5 were compared. In addition, the DNA-binding properties of STF1 and HY5 were extensively studied using random binding site selection and electrophoretic mobility shift assay. Overexpression of STF1 in the hy5 mutant of Arabidopsis restored wild-type photomorphogenic and root development phenotypes of short hypocotyl, accumulation of chlorophyll, and root gravitropism with partial restoration of anthocyanin accumulation. This supports that STF1 is a homolog of HY5 with a role in light and hormone signaling. The DNA-binding properties of STF1 and HY5 are shown to be similar to each other in recognizing many ACGT-containing elements with a consensus sequence motif of 5'-(G/A)(G/A) TGACGT(C/G/A)(A/T/G)-3'. The motif represents a characteristically strong preference for flanking sequence to TGACGT and a larger sequence than the sequences recognized by the G-box binding factor and TGA protein families. The finding of C-box, hybrid C/G-, and C/A-boxes as high-affinity binding sites over the G-box and parameters associated with HY5 recognition define the criteria of HY5/STF1 protein-DNA interaction in the promoter regions. This study helps to predict the precise in vivo binding sites of the HY5 protein from the vast number of putative HY5 genomic binding sites analyzed by chromatin immunoprecipitation on chip.
长下胚轴5（HY5）是一种bZIP（碱性亮氨酸拉链）转录因子，可激活拟南芥（Arabidopsis thaliana）中的光形态建成和根系发育。此前，在大豆中报道了STF1（大豆[Glycine max] TGACG基序结合因子1），一种具有环指基序和bZIP结构域的豆科同源蛋白。为了研究STF1的作用，比较了过表达STF1和HY5的转基因拟南芥植株的表型。此外，利用随机结合位点筛选和电泳迁移率变动分析对STF1和HY5的DNA结合特性进行了广泛研究。在拟南芥的hy5突变体中过表达STF1恢复了野生型光形态建成和根系发育表型，即下胚轴短、叶绿素积累以及根向地性，同时花青素积累部分恢复。这支持了STF1是HY5的同源物，在光和激素信号传导中发挥作用。STF1和HY5的DNA结合特性在识别许多含ACGT的元件时彼此相似，共有序列基序为5'-(G/A)(G/A)TGACGT(C/G/A)(A/T/G)-3'。该基序对TGACGT侧翼序列表现出明显的强烈偏好，且序列比对G-box结合因子和TGA蛋白家族识别的序列更大。发现C-box、杂交C/G-和C/A-box作为比G-box具有更高亲和力的结合位点以及与HY5识别相关的参数定义了启动子区域中HY5/STF1蛋白-DNA相互作用的标准。这项研究有助于从通过芯片染色质免疫沉淀分析的大量假定HY5基因组结合位点中预测HY5蛋白在体内的精确结合位点。
