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Role of RecA in DNA replication

Role of RecA in DNA replication. Yadi Zhou 2013.12.05. RecA protein. 38 kiloDalton Essential for the repair and maintenance of DNA A RecA structural and functional homolog has been found in every species Homologous protein in Homo sapiens is RAD51

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Role of RecA in DNA replication

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  1. Role of RecA in DNA replication Yadi Zhou 2013.12.05

  2. RecA protein • 38 kiloDalton • Essential for the repair and maintenance of DNA • A RecA structural and functional homolog has been found in every species • Homologous protein in Homo sapiensis RAD51 • Important enzyme in homologous recombination • Induce SOS response

  3. Structure

  4. RecA filament RecA-dsDNA

  5. Homologous recombination

  6. Homologous recombination

  7. SOS response

  8. E. coli strains deficient in RecA are useful • Potential drug target

  9. References • http://www.callutheran.edu/BioDev/omm/reca/recamast.htm • http://en.wikipedia.org/wiki/RecA • Nature Reviews Molecular Cell Biology 8, 127-138 (February 2007) • http://www.callutheran.edu/BioDev/omm/reca/recamast.htm • Nature 453, 463-466(22 May 2008)

  10. Thank you!

  11. Mechanisms of RecA DNA Repair Vivian Lesende December 5, 2013 BIOS 7200

  12. DNA Damage • Can arrest replication --- deletions/genomic rearrangements, point mutations, lethality • Many types of lesions can inhibit normal progression of replication forks -UV radiation – cis, syn-cyclobutane pyrimidine dimer (CPD) & pyrimidine-6-4-pyrimidone photoproduct (6-4 PP)

  13. RecA Functions • RecA functions to recover replication forks in several different ways -acts as transactivator for upregulating over 40 genes (SOS response) -protects single stranded DNA from degradation while replication is arrested -promotes recombination repair

  14. SOS Response • LexA-- repressor binds to a 20 bp consensus sequence in operator region in DNA-damage inducible genes • RecA bound to damaged single stranded DNA causes autocatalytic cleavage • Increases transcription of genes involved in SOS Response

  15. Genes Involved in SOS Response • Genes that function to remove lesions and restore replication • uvrA&uvrB-- recognize UV-induced lesions • ydjQ(cho) -- incision step for excision repair • polB, dinB, umuC&umuD– DNA polymerases Pol II, PolI V, Pol V

  16. SOS Response Courcelle & Hanawalt. Annu. Rev. Genet. 2003. 37:611-46

  17. Prevention of Degradation of Single-Stranded DNA of Replication Forks • RecA maintains structure of replication forks until replication resumes • Allows for nucleotide excision repair to occur • recA mutants have high sensitivity to UV-light – “rec-less” degradation

  18. Prevention of Degradation of Single-Stranded DNA of Replication Forks Courcelle & Hanawalt. Annu. Rev. Genet. 2003. 37:611-46

  19. Recombination Recovery • “postreplication repair” or “daughter-strand gap repair” • RecA promotes recombination as an alternative to excision repair – does not remove lesions from DNA • Typically only occurs if previous mechanisms have failed

  20. Recombination Recovery Courcelle & Hanawalt. Annu. Rev. Genet. 2003. 37:611-46

  21. References • J. Courcelle & P. C. Hanawalt. RecA-Dependent Recovery of Arrested DNA Replication Forks. Annu. Rev. Genet. 2003. 37:611-46

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