Regulation of expression of heat-shock proteins in cyanobacteria and studies on multi-chaperone complexes

蓝藻热激蛋白表达调控及多伴侣复合物研究

• 批准号: 13640640
• 负责人: NAKAMOTO Hitoshi
• 金额: $ 2.24万
• 依托单位: SAITAMA UNIVERSITY
• 依托单位国家: 日本
• 项目类别: Grant-in-Aid for Scientific Research (C)
• 财政年份: 2001
• 资助国家: 日本
• 起止时间: 2001 至 2002
• 项目状态: 已结题
• 来源: https://kaken.nii.ac.jp/grant/KAKENHI-PROJECT-13640640/
• 关键词: Cyanobacteria; Heat-shock protein; Molecular chaperone; Gene expression; Sigma factor; HtpG; HtpG; 発現調節

1. Regulation of transcription of cyanobacterial heat-shock protein (Hsp) genes(1) A novel Hsp, Orf7.5, did not bind to 5'-upstream region of groEL operon from Synechococcus PCC 7942, but interacted with the major sigma factor, enabling it to bind to the region. We postulate that Orf7.5 together with the major sigma factor is involved in a positive regulation of the operon. (2) An hrcA disruptant of Synchocystis PCC 6803 was constructed. With the mutant, we showed that the groEL genes are regulated by a negative mechanism (CIRCE/HrcA system) and a positive one that is yet to be clarified. (3) We detected a protein in the unstressed cells of the thermophilic cyanobacteriurn Synechococcus that specifically binds to a 5'-untranslated region of the hspA gene that encodes a small Hsp homologue. The time course of the DNA binding by the protein and the hspA mRNA level were inversely correlated. (4) The heat shock response is generally characteirized by an immediate, intense and transient activation of gene expression. We found that light modulates these characteristics of the heat shock response in cyanobacteria.2. Post-transcriptional regulation of heat shock genes.A downstream box (DB) sequence was found to exist in the coding sequence of the hspA gene. We postulated that the interaction of DB with 16S rRNA results in the stabilization of the hspA mRNA and the increase of its translation.3. Cellular functions of HtpGPhenotypic analyzes of an htpG disruptant of Synechococcus PCC 7942 showed that HtpG plays roles in cold acclimation and protection from oxidative stress as well as in thermo-tolerance.4. Multi-chaperone complexA novel, high-molecular-weight complex containing GroEL, DnaK and an unknown 48-kDa protein accumulated at 16℃, but the accumulation was strongly inhibited in the htpG disruptant, indicating that HtpG is involved in the formation of the complex.

1. 蓝藻热休克蛋白（Hsp）基因转录的调控（1）一种新的Hsp Orf7.5不与聚球藻PCC 7942的groEL操纵子的5'上游区域结合，但与主要的sigma因子相互作用，使其能够与该区域结合，我们假设 Orf7.5 与主要 sigma 因子一起参与了该区域的正向调节。 (2) 构建了集胞藻 PCC 6803 的 hrcA 突变体，我们发现 groEL 基因受到负性机制（CIRCE/HrcA 系统）和尚待阐明的正性机制的调节。 ）我们在嗜热蓝细菌聚球藻的未受应激细胞中检测到一种蛋白质，该蛋白质特异性结合到该细菌的 5'-非翻译区。编码小Hsp同源物的hspA基因与hspA mRNA水平的DNA结合的时间进程呈负相关(4)热休克反应的特征通常是基因表达的立即、强烈和短暂的激活。我们发现光可以调节蓝藻热激反应的这些特征。2．热激基因的转录后调控。在hspA的编码序列中发现了下游box（DB）序列。我们推测DB与16S rRNA的相互作用导致hspA mRNA的稳定及其翻译的增加。3.聚球藻PCC 7942 htpG破坏株的HtpG表型巢的细胞功能表明HtpG在冷驯化中发挥作用。以及免受氧化应激和耐热性的保护。4。含有GroEL、DnaK和未知48-kDa蛋白的高分子量复合物在16℃下积累，但在htpG破坏子中积累受到抑制，表明HtpG参与了复合物的形成。