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The Role of RecA in DNA Replication

The Role of RecA in DNA Replication. Hazem Dawoud. http://www.callutheran.edu/BioDev/omm/reca/recamast.htm. Outline. * introduction. * RecA binding sites. * RecA functions and activities. * SOS response. * TLS * RecA filament formation on DNA.

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The Role of RecA in DNA Replication

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  1. The Role of RecA in DNA Replication Hazem Dawoud http://www.callutheran.edu/BioDev/omm/reca/recamast.htm

  2. Outline * introduction. * RecA binding sites. * RecA functions and activities. * SOS response. * TLS * RecA filament formation on DNA. * Repair of a collapsed replication fork by RecA protein.

  3. DNA replication

  4. DNA Replication

  5. RecA protein : 38 kilodalton polypeptide. identified in E. coli by Clark and Margulies in 1965. DNA repair and maintenance. Class of homologous DNA repair protein. More than one DNA binding site. DNA dependent ATPase : allosteric enzyme.

  6. RecA Binding sites: DNA binding sites. ATP binding sites Nature Reviews Molecular Cell Biology 8, 127-138 (February 2007) |

  7. RecA protein functions: Repair of stalled replication fork double-strand break repair general recombination induction of the SOS response SOS mutagenesis Promotes mutagenic Trans-Lesion Synthesis by polV. Annu Rev Microbiol. 2003;57:551-77. Cox MM.

  8. Activities of Escherichia Coli RecA: a-Strand invasion reaction d-The replication fork regression reaction b- a three-strand-exchange reaction e- the RecA coprotease function. C-a four-strand-exchange reaction. f- stimulation of translesion -DNA-replication activity of DNA pol 5 Nature Reviews Molecular Cell Biology 8, 127-138 (February 2007) |

  9. The SOS Respose: In non-induced growth conditions, the LexA repressor binds to SOS-controlled promoters, limiting or preventing their action. RecA filaments formed at sites of damage activate the autocleavage of the LexA repressor, allowing SOS gene expression. SOS induction is reversed when damages are repaired. PLoS Biol. 2005 July; 3(7): e255. Bénédicte Michel

  10. TLS : Trans-Lesion SynthesisDNA damage tolerance process Involves switching out regular DNA pol with specialized trans-lesion pol. Low fidelity on the undamaged template. PCNA, proliferating cell nuclear antigen, provides a platform for TLS Pol.

  11. recombination repair

  12. Assembly of RecA filaments: Cox Nature Reviews Molecular Cell Biology8, 127–138 (February 2007) | doi:10.1038/nrm2099

  13. RecA protein Filament Formation on DNA. RecA protein filaments are generally formed in two distinct phases, nucleation and extension. Extension proceeds largely in the 5to 3direction, and cancontinue readily into any adjacent duplex DNA. Critical Reviews in Biochemistry and Molecular Biology, 42:41–63, 2007, Michael M. Cox

  14. Repair of a collapsed replication fork. RecA bind to ss DNA and catalyze hyperdization. RecA catalyze invasion of duplex DNA.

  15. Summary * RecA protein is DNA binding protein with multiple activiries. * RecA protein polymerize to form nucleoprotein filament. *RecA protein promotes mutagenic TLS by pol V. * RecA protein induces the SOS respose. * RecA promotes strand invasion to initiate recombination. * RecA protein repair of stalled replication fork.

  16. Thank You 謝謝 شكرا شکرید

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