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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.
* Repair of a collapsed replication fork by RecA protein.
DNA replication
DNA Replication
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.
RecA Binding sites:
DNA binding sites.
ATP binding sites
Nature Reviews Molecular Cell Biology 8, 127-138 (February 2007) |
RecA protein functions:
Repair of stalled replication fork
double-strand break repair
general recombination
induction of the SOS response
SOS mutagenesis
Promotes mutagenic TransLesion Synthesis by polV.
Annu Rev Microbiol. 2003;57:551-77. Cox MM.
Activities of Escherichia Coli RecA:
a-Strand invasion
reaction
b- a three-strandexchange reaction
C-a four-strandexchange reaction.
Nature Reviews Molecular Cell Biology 8, 127-138 (February 2007) |
d-The replication
fork regression
reaction
e- the RecA
coprotease function.
f- stimulation of
translesion -DNAreplication activity
of DNA pol 5
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
TLS :
Trans-Lesion SynthesisDNA damage tolerance
process
PCNA, proliferating cell nuclear antigen,
provides a platform for TLS Pol.
Involves switching out regular DNA pol with
specialized trans-lesion pol.
Low fidelity on the undamaged template.
recombination repair
Assembly of RecA filaments:
Cox Nature Reviews Molecular Cell Biology 8, 127–138 (February 2007) | doi:10.1038/nrm2099
01/09/12
RecA protein Filament Formation on DNA.
RecA protein filaments
are generally formed in two
distinct phases, nucleation
and extension.
Extension proceeds largely in
the 5 to 3 direction, and
cancontinue readily into any
adjacent duplex DNA.
Critical Reviews in Biochemistry and Molecular Biology, 42:41–63, 2007, Michael M. Cox
Repair of a collapsed
replication fork.
RecA bind to ss DNA and
catalyze hyperdization.
RecA catalyze invasion of
duplex DNA.
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.
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