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
第七章
细菌应激反应
Bacterial Stress Responses
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
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
anscriptional 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
Model for the mechanism of action of RssB in regulating S degradation by ClpXP.
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),
• 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.
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
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.