水稻蔗糖合成酶催化蔗糖與 UDP 形成果糖與 UDPG 的可逆反應,水稻中有三種蔗糖合成酶 (簡稱 RSus) 基因 (RSus1, RSus2, RSus3),三種 RSus 基因在水稻不同組織中的表現不盡相同,其中發現 RSus1 與 RSus2 在不同組織普遍皆有表現,而 RSus3 的表現則有種子專一性。本研究以水稻懸浮培養細胞 (Oryza sativa L. cv. Tainung 67 ) 為材料,探討細胞以不同方式處理後所抽取得之核蛋白質,是否與 RSus1 基因 5’ 端的調控區域之間有交互作用。由電泳遲滯分析及 DNA 足跡實驗的結果得知,在 RSus1 轉錄起始點上游 -1117 bp ~ -750 bp 的序列中存有四個蛋白質結合區域。分析這些結合區域之序列後,發現含有四種不同的 elements。此外,水稻懸浮細胞經由蔗糖及 cycloheximide 培養後,將抽取得之核蛋白質進行電泳遲滯分析實驗發現,DNA-蛋白質複合體的色帶減少。此結果顯示,核蛋白質在 RSus1 調控區域上 cis-elements 的結合,可能需蔗糖存在。
Sucrose synthase catalyzes the reversible conversion of sucrose and UDP into fructose and UDPG. The enzyme is encoded by three differentially expressed genes, RSus1, RSus2 and RSus3, in rice. The gene products of RSus1 and RSus2 are ubiquitously present in various rice tissues, while the expression of RSus3 is seed-specific. In this study, we investigated whether the 5’ control region of RSus1 could interact with nuclear proteins from suspension-culture cells of rice (Oryza sativa L. cv. Tainung 67) under different treatments. The results of gel retardation and DNase I footprinting suggest that there are four protein-binding regions between -1117 bp and -750 bp upstream the transcription initiation site of RSus1. Sequence analysis of these four protein-binding regions revealed four distinct elements. When gel retardation experiments were performed with nuclear proteins extracted from cells cultured in the presence of sucrose and cycloheximide, the formation of DNA-protein complexes diminished. The results indicate that binding of proteins to the cis-elements in the gene control region of RSus1 may be sucrose-dependent.