MCB 7200

Group 1Ashley PattonYanyang CuoSamantha Shaw

Biological Relevance◦ Repairs double-stranded breaks◦ Chromosome segregation during meiosis I◦ Genetic diversity in gametes

Mediated by two important enzymes◦ Rad51 and Dmc1

Occurs during late-S phase, G2, M

Filippo et al. 2008. Mechanism of Eukaryotic Homologous Recombination

Double Strand Break Repair

Synthesis-dependent strand annealing ◦ Migrating D loop◦ No Holiday Junction formation◦ Mitosis/Meiosis

Single strand annealing◦ Repair of double strand break by deletion of repeated DNA

sequences ◦ No Holiday Junction formation

Break-induced repair◦ Telomeres ◦ Replication forks

Filippo et al. 2008. Mechanism of Eukaryotic Homologous Recombination

RecBCD◦ Helicase activity unwinds

DNA◦ Exonuclease activity

degrades both single strands◦ At CHI site

3′ - 5′ Exonuclease activity is inhibited

5′ -3′ activity enhanced yielding a single-stranded 3′ end. This end becomes coated

with multiple RecA proteins, which catalyze strand invasion and formation of a Holliday structure

Lodish et al., Molecular Cell Biology, 4 th Fig 12-32

RecA◦ RecA binds ssDNA in the presence of ATP◦ RecA aligns the ssDNA with its

homologous dsDNA region◦ RecA inserts the ssDNA into target DNA

sequence forming a heteroduplex Holiday-type structure

Branch Migration and Resolution by RuvA,B,C

Lodish et al., Molecular Cell Biology, 4 th Fig 12-35

http://www.qiagen.com/products/genes%20and%20pathways/pathway%20details.aspx?pwid=143

http://www.qiagen.com/products/genes%20and%20pathways/pathway%20details.aspx?pwid=143

Filippo et al. 2008. Mechanism of Eukaryotic Homologous Recombination

Used for double strand break repair and genetic diversity in meiosis.

Different mechanisms within the Eukaryotic and Prokaryotic cells.

Proteins are different with each system by have similar functions.

C. Wyman et al. /DNA Repair 3 (2004) 827–833

Fillipo et al. Mechanism of Eukaryotic Homologous Recombination. 2008. Annual Rev. Biochem. 77:229-57.

Lodish et al. Molecular Cell Biology. 1999. W. H. Freeman. 4th edition. Oldenburg et al. Recombination-mediated PCR directed plasmid construction in

vivo in yeast. 1997. Nucleic Acids Research. Vol. 25, No. 2. Wyman et al. Homologous recombination-mediated double-strand break repair.

(2004) DNA Repair. 3:827–833.