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.蓝藻热休克蛋白基因转录调控(1)一种新的热休克蛋白Orf7.5不与聚球藻PCC7942的GroEL操纵子5‘-上游区域结合，但与主要的西格玛因子相互作用，使其能够与该区域结合。我们推测Orf7.5与主要的西格玛因子一起参与操纵子的正向调节。(2)构建了合胞藻PCC6803的hrcA干扰物。通过突变体，我们证明了GroEL基因受一种负的机制(Circe/HrcA系统)和一种尚不清楚的正机制的调控。(3)我们在嗜热蓝藻聚球藻的非应激细胞中检测到一种蛋白质，它特异性地结合到HSPA基因的5‘-非翻译区，编码一个小的HSP同源物。蛋白质与DNA结合的时间进程与HSPA mRNA水平呈负相关。(4)热休克反应一般表现为基因表达的即刻、强烈和瞬间激活。我们发现，光调制了蓝藻热休克反应的这些特征。热休克基因转录后调控：在HSPA基因的编码序列中发现了下游的盒(DB)序列。我们推测DB与16S rRNA的相互作用导致HSPA mRNA的稳定和翻译的增加。HtpG的细胞功能表型分析表明，HtpG在冷驯化、氧化应激保护和耐热性等方面具有重要作用。多分子伴侣复合体一种新型的高分子复合体，包含GroEL、DNAK和一个未知的48℃蛋白质，在16 kDa处积累，但这种积累在HTPG干扰物中被强烈抑制，表明HtpG参与了复合体的形成。

项目成果

K.Kojima: "Specific binding of a protein to a novel DNA element in the cyanobacterial small heat-shock protein gene"Biochemical and Biophysical Research Communications. 297・3. 616-624 (2002)

K. Kojima：“蓝藻小热休克蛋白基因中蛋白质与新型 DNA 元件的特异性结合”生物化学和生物物理研究通讯 297・3（2002）。

H.Nakamoto: "Heat shock response in cyanobacteria"CACS FORUM. 22. 20-26 (2002)

H.Nakamoto：“蓝藻细菌的热休克反应”CACS FORUM。

M.M.Hossain: "Role for the cyanobacterial HtpG in protection from oxidative stress"Current Microbiology. 46・1. 70-76 (2003)

M.M.Hossain：“蓝藻 HtpG 在防止氧化应激中的作用”当前微生物学 46・1（2003 年）。

M.M.Hossain: "HtpG plays a role in cold acclimation in cyarobacteria"Current Microbiology. 44. 291-296 (2002)

M.M.Hossain：“HtpG 在蓝细菌的冷驯化中发挥着作用”《当代微生物学》。

Md.Motarab Hossain: "HtpG plays a role in cold autimation in cyanobacteria"Current Microbiology. 44・4. 291-296 (2002)

Md.Motarab Hossain：“HtpG 在蓝细菌的冷自动化中发挥作用”《当代微生物学》44・4（2002）。