Bacterial Stress Responses

Presentation on theme: "Bacterial Stress Responses"— Presentation transcript:

1 Bacterial Stress Responses
第七章 细菌应激反应 Bacterial Stress Responses

2 Main content 微生物的应激反应定义与分类 通用调节途径 热休克反应 氧压力 渗透压 蛋白质组学在细菌应激反应研究中的应用

3 Bacterial Stress Responses
General stress response Activation of RpoS (σ38) by cessation of growth Induction of Pol IV, error prone polymerase Heat-shock response Activation of RpoH (σ32), induction of GroE GroE protects Pol V from degradation Stringent response Amino acid deprivation, starvation Mediated by guanosine tetraphosphate, ppGpp Enhances RpoH and RpoS responses SOS response Triggered by damage to DNA LexA-RecA mediated

4 stress response systems
细菌多生于动态多变的环境中(温度,pH,压力,氧化,营养,以及各种化学物质刺激等),细菌存在一个整体调控网络可以快速调节大量基因表达来快速适应这种环境变化,这种调控网络被称为stress response系统. stress response systems在细菌中高度相似的,有一些在真核细胞和古菌中也是保守的(如热休克反应). 不同菌见,激活stress response 条件不一样

5 1975年O’Farrell2D研究E.coli heat-shock proteins,2003年Hatfield用microarray研究应激反应.
基因表达-转录,转录后调控,细菌中转录调控为主. DNA-dependent RNA polymerase, (five subunits a2bb’w) 和an additional subunit (σ). E. coli有7个sigma factors: σ 70 and the vegetative sigma factors, RpoD, RpoN, RpoS, RpoH, RpoF, RpoE, and FecI. 这些σ因子通过竞争和RNase核心酶结合,对转录调控起主要租用,另外转录抑制因子,激活因子, σ结合因子, 抗σ因子,以及一些小RNAs的调控起辅助作用.

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7 Regulation of RpoS Expression
RpoS is induced during the transition from exponential phase to stationary phase or in response to various stress conditions,引起细胞生理和形态的改变 RpoS的表达受严格控制at the transcriptional, translational, and posttranslational levels

8 nlpD Fis, a global transcriptional factor, inhibits rpoS transcription by directly binding to the rpoS promoter region. Fis levels are growth-phase dependent. At the onset of stationary phase, Fis disappears and the transcription of rpoS is induced

9 Model for the mechanism of action of RssB in regulating S degradation by ClpXP.

10 RpoS, a Master Regulator in Stress Response and Adaptation
More than 10% of the E. coli genome is controlled by RpoS, most of which is involved in stress response, such as nutrient limitation resistance to DNA damage, osmotic shock high hydrostatic pressure, oxidative stress, ethanol resistance, adaptive mutagenesis, acid stress, and biofilm formation. RpoS controls a more degenerate promoter sequence featuring a −10 region (TAYACT),

11 Heat-shock response In E. coli heat-shock induces pproximately 30 genes under control of another sigma factor, RpoH (32). The RpoH-regulon is also induced by unfolded proteins Levels of DNA Pol V are dependent on GroE because the chaperon interacts with the polymerase subunit of PolV and protects it from degradation The groEL/ES operon, which encodes the molecular chaperone GroE, is an important member of this regulon.

12 Heat-shock response in bacteria
heat-shock responsive genes have specific sequences in their promoters which replace the common -35 and -10 regions: these promoters are recognized byσ32 σ32 is encoded by the rpoH gene. The mRNA is stabilized by heat-shock leading to increased translation. In E. coli heat-shock induces approximately 30 genes under control of another sigma factor, RpoH.

13 Heat Shock Response in Eukaryotes
also have specific sequences, in this case upstream of heat-shock genes - HSE (Heat Shock Element) This is bound by (HSF) Heat Shock Factor, trimerizes using a leucine zipper. HSF is phosphorylated as a consequence of heat shock - this activates it and allows transcription to take place from the promoter

14 σ32(RpoH), the heat shock sigma factor, is rapidly degradedunder normal growth conditions by the AAA protease,FtsH, in a reaction modulated by the DnaJ/DnaK/GrpE chaperone system. During heat shock, 32 is transiently stabilized, and this stabilization results in the rapid increase in the synthesis of the heat shock proteins (Yura and Nakahigashi 1999).

15 大肠杆菌中的活性氧造成的损伤 RpoS OxyR SoxRS

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19 金黄葡萄球菌中的抗宿主氧化损伤机制

20 渗透压应激反应 ompF基因有ompR产物的高亲和位点 ompC基因有ompR产物的低亲和位点 。

21 SOS反应 When bacteria are subjected to DNA damage about 30 genes are coordinately induced, a reaction known as the “SOS response”. SOS genes may be induced to some degree under a variety of stressful conditions

22 针对不同环境信号，细菌通过调节多种细胞内酶的数量和活性来适应新环境，涉及蛋白种类多。细菌应激反应不仅仅是一两个蛋白的作用能够解释清楚的，需要从整体水平对细菌蛋白表达谱进行分析
细菌转录即翻译、mRNA半衰期短、，没有polyA尾巴 2D技术能直观显示细胞中每种蛋白的变化，是研究应激反应的利器

23 总结 1、 2、 3、 4、