Chapter 5 General Recombination Repair of replication forks
Chapter 5 • General Recombination
Repair of replication forks Figure 5 -53 (part 1 of 2) Molecular Biology of the Cell (© Garland Science 2008)
Repair of replication forks Figure 5 -53 (part 2 of 2) Molecular Biology of the Cell (© Garland Science 2008)
General recombination transfers information from one DNA strand to another
DNA crossovers create heteroduplex DNA
General recombination in meiosis
ds break General recombination in meiosis synapse strand invasion heteroduplex formation branch migration resolution
Recombination is similar to DNA hybridization
Resolution of recombination depends on where breaks occur Patch Splice
Spo 11 Rec. BCD/MRN Rec. A DNA pol Ruv. A-Ruv. B Ruv. C
Rec. BCD Helicase/Nuclease Processes DS breaks to form ss. DNA ends Loads Rec. A onto the ss. DNA ends Destroys foreign DNA Binds ends and tracks along the DNA - ATP hydrolysis
The Rec. BCD complex prepares DNA ends for homologous recombination
Chi sites increase the rate of homologous recombination
The structure of the Rec. A/Rad 51 filament
Rec. A/Rad 51 filaments
Rec. A catalyzes synapse formation
How does a broken strand find a homologous donor? Triplex DNA formed by base “flipping”? Rapid Exchange of A: T Base Pairs Is Essential for Recognition of DNA Homology by Human Rad 51 Recombination Protein Ravindra C. Gupta, * Ewa Folta-Stogniew, † Shawn O’Malley, * Masayuki Takahashi, ‡ and Charles M. Radding*†§ Molecular Cell, Vol. 4, 705– 714, November, 1999, Rad 51
Rec. A contains two DNA binding sites
Rec. A catalyzes branch migration
Figure 5 -58 Molecular Biology of the Cell (© Garland Science 2008)
The Holliday junction
A EM micrograph of a Holliday junction
Ruv proteins catalyze double branch migration Ruv. A: Holiday junction binding protein (tetramer) Ruv. B: ATP dependent helicase (hexamer)
An alternate representation of Ruv. AB
Ruv. C resolves Holiday structures
Spo 11 Rec. BCD MRX complex Mre 11, Rad 50 Xrs 2 (Nbs 1) Rec. A DNA pol Ruv. A-Ruv. B Ruv. C Rad 51, Dmc 1 BRCA 1, BRCA 2
DS break repair Figure 5 -59 Molecular Biology of the Cell (© Garland Science 2008)
Gene conversion
Gene conversion Figure 5 -63 Molecular Biology of the Cell (© Garland Science 2008)
Heteroduplex formation at sites of gene conversion and crossover Figure 5 -65 Molecular Biology of the Cell (© Garland Science 2008)
Gene conversion by mismatch correction Figure 5 -66 Molecular Biology of the Cell (© Garland Science 2008)
Resolution of recombinant intermediates in meiotic and mitotic cells
Resolution of recombination depends on where breaks occur Patch Splice
Mismatch detection prevents recombination of similar sequences
Recombination controls yeast mating types
Chapter 5 • Site-Specific Recombination
The human genome contains many transposable elements
Table 5 -3 Molecular Biology of the Cell (© Garland Science 2008)
Bacterial transposable elements
Cut-and-paste transposition
The structure of a transposase bound to DNA
Replicative cut-and-paste transposition
Retrovirus lifecycle Figure 5 -71 Molecular Biology of the Cell (© Garland Science 2008)
Structure of reverse transcriptase Figure 5 -72 a Molecular Biology of the Cell (© Garland Science 2008)
Structure of reverse transcriptase Figure 5 -72 b Molecular Biology of the Cell (© Garland Science 2008)
Transposition of retroviral like transposable elements
Transposition of non-retroviral like transposable elements Figure 5 -74 (part 1 of 2) Molecular Biology of the Cell (© Garland Science 2008)
Transposition of non-retroviral like transposable elements Figure 5 -74 (part 2 of 2) Molecular Biology of the Cell (© Garland Science 2008)
Expansion of repetitive elements in mouse and human lineages Figure 5 -75 Molecular Biology of the Cell (© Garland Science 2008)
Transposable elements near the -globin gene cluster Alu - green L 1 - red Bl - blue L 1 - yellow
The human genome contains many transposable elements
Table 5 -3 Molecular Biology of the Cell (© Garland Science 2008)
Conservative site-specific recombination can rearrange DNA
Insertion of lambda DNA into a bacterial chromosome
Insertion of lambda DNA into a bacterial chromosome att. P att. B Integration Host Factor (IHF) att. L att. R
The lambda phage life cycle
Use of site-specific recombination to control gene expression
Inactivation of a marker gene by recombination
Inactivation of a marker gene by recombination Figure 5 -79 Molecular Biology of the Cell (© Garland Science 2008)
Inactivation of a marker gene by recombination Figure 5 -79 a Molecular Biology of the Cell (© Garland Science 2008)
Figure 5 -79 b Molecular Biology of the Cell (© Garland Science 2008)
Points to understand: The differences between site-specific and general recombination The consequences of each type of recombination The three types of transposable elements How the elements move How the TEs relate to viruses and phage Conservative site specific recombination and how it is used by cells and experimental biologists
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