lecture7

Lecture7 - DNA Repair single step photo lyases base excision repair nucleotide excision repair mismatch repair double stranded break repair 701

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701 DNA Repair single step: photo lyases base excision repair nucleotide excision repair mismatch repair double stranded break repair
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702 Double stranded breaks (DSBs) - caused by ionizing radiation/free radicals - repaired by non homologous end-joining (NHEJ) - ends are aligned by Ku70 and Ku80
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703 Endjoining (error prone)
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704 Xeroderma Pigmentosa (XP): - mutation in NER enzymes > 2000fold increase in probability of skin cancer Cockayne Syndrome (CS) - mutation in CSA and CSB - defect in transcription-coupled repair - extreme UV sensitivity Human Diseases due to defects in DNA Repair systems
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705
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706 E.coli SOS response LexA and RecA DNA binding proteins regulate the SOS response upon DNA damage cells stop dividing normally LexA represses SOS response genes damaged DNA, single stranded binds to RecA, inactivating LexA allowing for gene expression new DNA does not contain RecA, and so LexA can repress SOS genes SOS response: activates expression of 43 genes e.g. recA, lexA, uvrR, uvrB, DNA polymerase IV and V (error prone)
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707 Human DNA Repair and the Cell cycle DNA repair - before S - before M p53 - the guardian of the genome controls DNA repair and cell cycle arrest at G1 and G2
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708 Mutations in p53 found in human cancers human cancer cells reveal which proteins are important for DNA damage response > 50% of human cancers show mutations in p53 Bob Weinberg, Whitehead Institute, MIT p53 - the guardian of the genome
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709 DNA Recombination
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710 General Recombination Robin Holliday 1964 two ways of resolving Holliday junctions
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711 Holliday junctions
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712 RecA protein 352 aa promotes recombination polymerizes on ss and ds DNA 6.2 monomers per turn turn is 18.6 nt or bp partially unwinds DNA promotes strand exchange by stabilizing 3-stranded intermediate
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713 Two proposed Models for RecA-mediated pairing and strand exchange ssDNA and dsDNA dsDNA and dsDNA base rotation
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714 ssDNA and dsDNA dsDNA and dsDNA RecA mediated strand exchange
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715 Preparing for recombination generating a 3’ overhand by RecBCD
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716 RuvA binds holiday junction RuvB is ATPase RuvC is nuclease, cuts apart recombinant duplexes (j) RuvABC mediate branch migration
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This note was uploaded on 10/30/2010 for the course CHEM 114C taught by Professor Alexanderhoffmann during the Spring '08 term at UCSD.

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Lecture7 - DNA Repair single step photo lyases base excision repair nucleotide excision repair mismatch repair double stranded break repair 701

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