How does synthesis-dependent strand annealing work?
Synthesis-dependent strand-annealing (SDSA)-mediated homologous recombination replaces the sequence around a DNA double-strand break (DSB) with a copy of a homologous DNA template, while maintaining the original configuration of the flanking regions.
What is Sdsa in biology?
Synthesis-dependent strand annealing (SDSA) is a major mechanism of homology-directed repair of DNA double-strand breaks (DSBs). The resulting single Holliday junction then slides down the DNA duplex in the same direction in a process called branch migration, displacing the extended strand from the template strand.
What is a double Holliday junction?
Double Holliday junctions (dHJS) are important intermediates of homologous recombination. The separate junctions can each be cleaved by DNA structure-selective endonucleases known as Holliday junction resolvases.
What is SDSA DNA repair?
Definition: SDSA is a major mechanism of double-strand break repair in mitosis which allows for the error-free repair of a double-strand break without the exchange of adjacent sequences. The broken DNA searches for and base pairs with a homologous region in an intact chromosome.
What is DSBR pathway?
Two primary models for how homologous recombination repairs double-strand breaks in DNA are the double-strand break repair (DSBR) pathway (sometimes called the double Holliday junction model) and the synthesis-dependent strand annealing (SDSA) pathway. The two pathways are similar in their first several steps.
What does Nhej stand for?
Non-homologous end joining (NHEJ) is a pathway that repairs double-strand breaks in DNA. NHEJ is referred to as “non-homologous” because the break ends are directly ligated without the need for a homologous template, in contrast to homology directed repair, which requires a homologous sequence to guide repair.
What is strand invasion in homologous recombination?
Upon finding such a sequence, the single-stranded nucleoprotein filament moves into the homologous recipient DNA duplex in a process called strand invasion. The invading 3′ overhang causes one of the strands of the recipient DNA duplex to be displaced, to form a D-loop.
How do you induce a double strand break?
DNA double-strand breaks (DSBs) are one of many types of DNA damage that occur spontaneously in all living organisms. DSBs can be induced by ionizing radiation, radiomimetic chemicals or reactive oxygen species, but also during DNA replication when a polymerase encounters a single-strand lesion at a replication fork1.
What is synthesis dependent strand annealing (SDSA)?
In addition to the model for DNA double strand break repair described in the Introduction, there is another class of models which we refer to here as Synthesis Dependent Strand Annealing or SDSA. In SDSA one strand invades and initiates DNA synthesis. One version is illustrated below. As synthesis proceeds the DNA also unwinds from the template.
What is SDSA model of DNA synthesis?
Strand Annealing In addition to the model for DNA double strand break repair described in the Introduction, there is another class of models which we refer to here as Synthesis Dependent Strand Annealing or SDSA. In SDSA one strand invades and initiates DNA synthesis. One version is illustrated below.
What is the SDSA model of repair of double stranded breaks?
In the SDSA model, repair of double-stranded breaks occurs without the formation of a double Holliday junction, so that the two processes of homologous recombination are identical until just after D-loop formation.
What causes double strand breaks in DNA?
Double-strand breaks (DSBs) are considered to be the most deleterious form of DNA damage. DSBs can be induced by exogenous agents such as ionizing radiation (IR), methyl methane sulfonate (MMS), camptothecin, hydroxyurea (HU), and endogenous metabolic products such as reactive oxygen species and stalled replication forks.