recombinational repair in bacteria

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Author:
chartreuse
ID:
287882
Filename:
recombinational repair in bacteria
Updated:
2014-11-02 17:43:44
Tags:
DNA repair
Folders:
Molecular Bio
Description:
recombinational DNA repair
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  1. main recombinase
    RecA
  2. initiator complexes
    • RecBCD
    • RecFOR
  3. RecBCD
    - what kind of enzyme?
    - what are its functions (2)?
    • helicase & nuclease - unwinds & degrades
    • 1. degrades 5' at DSB
    • -binds at free 5' & moves inward on the helix unwinding & degrading; coupled to ATP hydrolysis
    • 2. loads RecA onto ss-tail
  4. RecBCD component functions...
    • -helicase motors (B-moves 3'->5' on 1 strand & nuclease & loads RecA, D-moves 5'->3' on other)
    • - RecC binds chi on the 3' alters RecB degradation (stops on 3' & increases on 5')
  5. chi
    • -5'-GCTGGTGG-3' sequence on the 3'end at DSB
    • -binds RecC
    • -initiates 5' degradation = ss 3' tail
  6. SSB at 3'-ss tail
    ssDNA binding proteins block RecA etc.
  7. gap filling bacteria polymerase
    Pol I
  8. helicase at stalled replication fork promotes regression
    RecG
  9. RecA
    • -recombinase, loaded & nucleated by RecB of RecBCD complex facilitating strand invasion
    • - also must be loaded onto ssDNA gaps
    • - DNA-dependent ATPase, filament nucleoprotein causes extension of nucleated filament in 5'->3'
    • - align a ssDNA with homologous dsDNA & switching => strand invasion
    • -highly regulated
  10. loads RecA on ssDNA gaps
    • RecF of RecFOR
    • collectively activate & load RecA
  11. RecA regulation, 3 levels:
    • transcription
    • autoregulation
    • regulation by other proteins
  12. when does homologous recombination occur during meiosis?
    metaphase, meiosis I
  13. fork collapse repair mechanism
    • 1. RecBCD - 5' nuclease activity at break; recruitment of RecA
    • 2. RecA strand invasion (intact dsDNA seperates & aligns with 3' ss-tail)
    • 3. RuvAB branch migration (intact dsDNA continues to seperate & digested 5' aligns with other intact strand)
    • 4. RuvC & ligase cleavage at (3'->5' strand Y-cross) = Holliday intermediate resolution then ligation
  14. Ruv-complexes
    • RuvA tetramer - binds DNA Holliday intermediate 
    • RuvB - DNA translocase, coupled to ATP hydrolysis
    • RuvAB - & promotes branch migration
    • RuvC - resolvase
  15. what restarts replication?
    restart primosome complex loads replicative helicase DnaB onto DNA => rep. fork

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