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lecture_23 - Lecture23 RegulatoryResponses: SOSandHeatShock

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Lecture 23 Regulatory Responses: SOS and Heat Shock Reading 19.1 19.3, 19.4
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SOS: Mechanism to read through damaged and/or modified DNA
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What happens when cells are exposed to DNA damaging agents DNA damage occurs and causes, nicks, gaps, breaks, etc.
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Key enzymes: RecA: DNA recombination, activator for the system LexA: Repressor of SOS genes SulA: inhibitor of FtsZ, substrate for Lon Protease SOS inducable Lon: Protease, degrades SulA UmuDC : inhibit PolII proofreading (error prone), SOS inducable PolII: repair polymerase SOS inducible UvrABD: UV induced excision repair SOS inducible RuvA,B, RecN: Double strand Gap/break repair SOS inducible
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Model: In response to ss DNA fragments, nicks etc. Causes the activation of RecA Activated RecA (RecA*), aids in the autocleavage of LexA Removal of LexA causes initiation of SOS genes Repair functions to “fix” damage no more damage, leads to inactivation of RecA* LexA accumulates and shuts down the system
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require time to “fix” the damage Cell’s arrest cell division. But how?
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lecture_23 - Lecture23 RegulatoryResponses: SOSandHeatShock

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