Role of Saccharomyces Single-Stranded DNA-Binding Protein RPA in the Strand Invasion Step of Double-Strand Break Repair (original) (raw)
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Recruitment of the Recombinational Repair Machinery to a DNA Double-Strand Break in Yeast
Molecular Cell, 2003
viewed in Pâ ques and Haber, 1999; Sung et al., 2000). In the mouse, a homozygous null allele of RAD51 leads to embryonic lethality (Tsuzuki et al., 1996), and muta-Program in Molecular Medicine tions in RAD genes are associated with a spectrum of University of Massachusetts Medical School diseases, including cancer (reviewed in Ivanov and Ha-Worcester, Massachusetts 01605 ber, 1997; Jasin, 2000; Michelson and Weinert, 2000). 2 Institute of Biotechnology and Studies in yeast have suggested a sequence of molec-Department of Molecular Medicine ular events that occur following formation of a DSB (re-. First, the 5Ј ends of DNA that flank San Antonio, Texas 78245 the break are resected by an exonuclease. Rad51p, a functional homolog of the E. coli RecA recombinase, then binds the exposed single-stranded tails forming a right-Summary handed helical nucleoprotein filament. In vitro, Rad52p (Sung, 1997a) and a Rad55p/Rad57p heterodimer (Sung, Repair of DNA double-strand breaks (DSBs) by homol-1997b) can promote this early step by overcoming the ogous recombination requires members of the RAD52 inhibitory effects of the heterotrimeric single-stranded epistasis group. Here we use chromatin immunopre-DNA binding protein, RPA. The Rad51p nucleoprotein cipitation (ChIP) to examine the temporal order of filament is then believed to function in cooperation with recruitment of Rad51p, Rad52p, Rad54p, Rad55p, Rad54p to search the genome for a homologous pairing and RPA to a single, induced DSB in yeast. Our results partner and to form a heteroduplex "joint molecule" (Petsuggest a sequential, interdependent assembly of ukhova et al., 1998, 2000). Joint molecule formation is Rad proteins adjacent to the DSB initiated by binding followed by extension of the incoming strand by DNA of Rad51p. ChIP time courses from various mutant polymerases and branch migration, ultimately leading strains and additional biochemical studies suggest to restoration of the genetic information spanning the that Rad52p, Rad55p, and Rad54p each help promote break (reviewed in Pâ ques and Haber, 1999). the formation and/or stabilization of the Rad51p nu-Much less is known about how Rad proteins functioncleoprotein filament. We also find that all four Rad ally cooperate during DSB repair in vivo. Immunofluoresproteins associate with homologous donor sequences cence studies have shown that Rad51p, Rad52p, and during strand invasion. These studies provide a near Rad54p colocalize to "foci" in response to DNA damage comprehensive view of the molecular events required in vivo (Haaf et al., 1995; Tan et al., 1999), suggesting for the in vivo assembly of a functional Rad51p presynthat Rad proteins might function together within a larger, aptic filament. multiprotein complex. Consistent with this view, coimmunoprecipitation and yeast two-hybrid assays have Introduction shown that many members of the RAD52 group can interact with each other (Golub et al., 1997; Hays et al., DNA double-strand breaks (DSBs) arise in DNA due to 1995; Johnson and Symington, 1995; Krejci et al., 2001). environmental insults such as ionizing radiation or In contrast, recent studies indicate that the composition chemical exposure. DSBs also play an important role as of the damage-induced foci are dynamic, and photointermediates in DNA replication, immunoglobulin V(D)J bleaching studies indicate that several Rad proteins recombination, meiotic and mitotic crossing-over, and have very different diffusion coefficients, suggesting that yeast mating-type switching. Failure to correctly prothey may not exist together in a preassembled protein cess these DSBs can result in deletion or insertion of complex (Essers et al., 2002). genetic information, chromosomal fragmentation, trans-We wished to dissect how Rad proteins are recruited location, and chromosome loss. and function at a DSB in vivo. Here we use chromatin Homologous recombination (HR) is a major pathway immunoprecipitation (ChIP) analyses to examine the of DSB repair in all eukaryotes and has a distinct advantemporal order of Rad protein recruitment to a single, tage over other mechanisms in that it is mostly error induced DSB in yeast. Our results suggest a sequential free. Repair of DSBs by HR requires the RAD52 epistasis pathway, where Rad51p binds first, followed by Rad52p, group, defined by the yeast RAD50, RAD51, RAD52, Rad55p, and finally Rad54p. Each of these Rad proteins RAD54, RAD55, RAD57, RAD59, MRE11, and XRS2 genes. also associates with the homologous donor sequences These genes are highly conserved among all eukaryotes during strand invasion. We further examined the func-(Cromie et al., 2001; Pâ ques and Haber, 1999; Sung et tional interdependencies among these proteins by peral., 2000), highlighting the importance of these proteins
Aberrant Double-Strand Break Repair in rad51 Mutants of Saccharomyces cerevisiae
Molecular and Cellular Biology, 2000
A number of studies of Saccharomyces cerevisiae have revealed RAD51 -independent recombination events. These include spontaneous and double-strand break-induced recombination between repeated sequences, and capture of a chromosome arm by break-induced replication. Although recombination between inverted repeats is considered to be a conservative intramolecular event, the lack of requirement for RAD51 suggests that repair can also occur by a nonconservative mechanism. We propose a model for RAD51 -independent recombination by one-ended strand invasion coupled to DNA synthesis, followed by single-strand annealing. The Rad1/Rad10 endonuclease is required to trim intermediates formed during single-strand annealing and thus was expected to be required for RAD51 -independent events by this model. Double-strand break repair between plasmid-borne inverted repeats was less efficient in rad1 rad51 double mutants than in rad1 and rad51 strains. In addition, repair events were delayed and frequ...
Molecular and Cellular Biology, 2004
Mitotic double-strand break (DSB)-induced gene conversion involves new DNA synthesis. We have analyzed the requirement of several essential replication components, the Mcm proteins, Cdc45p, and DNA ligase I, in the DNA synthesis of Saccharomyces cerevisiae MAT switching. In an mcm7-td (temperature-inducible degron) mutant, MAT switching occurred normally when Mcm7p was degraded below the level of detection, suggesting the lack of the Mcm2-7 proteins during gene conversion. A cdc45-td mutant was also able to complete recombination. Surprisingly, even after eliminating both of the identified DNA ligases in yeast, a cdc9-1 dnl4⌬ strain was able to complete DSB repair. Previous studies of asynchronous cultures carrying temperaturesensitive alleles of PCNA, DNA polymerase ␣ (Pol␣), or primase showed that these mutations inhibited MAT switching (A. M. Holmes and J. E. Haber, Cell 96:415-424, 1999). We have reevaluated the roles of these proteins in G 2 -arrested cells. Whereas PCNA was still essential for MAT switching, neither Pol␣ nor primase was required. These results suggest that arresting cells in S phase using ts alleles of Pol␣-primase, prior to inducing the DSB, sequesters some other component that is required for repair. We conclude that DNA synthesis during gene conversion is different from S-phase replication, involving only leading-strand polymerization.
2013
Saccharomyces cerevisiae RAD50, MRE11, and XRS2 genes are essential for telomere length maintenance, cell cycle checkpoint signaling, meiotic recombination, and DNA double stranded break (DSB) repair via nonhomologous end joining and homologous recombination. The DSB repair pathways that draw upon Mre11-Rad50-Xrs2 subunits are complex, so their mechanistic features remain poorly understood. Moreover, the molecular basis of DSB end resection in yeast mre11-nuclease deficient mutants and Mre11 nuclease-independent activation of ATM in mammals remains unknown and adds a new dimension to many unanswered questions about the mechanism of DSB repair. Here, we demonstrate that S. cerevisiae Mre11 (ScMre11) exhibits higher binding affinity for single- over double- stranded DNA and intermediates of recombination and repair and catalyzes robust unwinding of substrates possessing a 3 single-stranded DNA overhang but not of 5 overhangs or blunt-ended DNA fragments. Additional evidence disclosed that ScMre11 nuclease activity is dispensable for its DNA binding and unwinding activity, thus uncovering the molecular basis underlying DSB end processing in mre11 nuclease deficient mutants. Significantly, Rad50, Xrs2, and Sae2 potentiate the DNA unwinding activity of Mre11, thus underscoring functional interaction among the components of DSB end repair machinery. Our results also show that ScMre11 by itself binds to DSB ends, then promotes end bridging of duplex DNA, and directly interacts with Sae2. We discuss the implications of these results in the context of an alternative mechanism for DSB end processing and the generation of single-stranded DNA for DNA repair and homologous recombination.
Molecular and cellular biology, 1995
HO endonuclease-induced double-strand breaks (DSBs) in the yeast Saccharomyces cerevisiae can be repaired by the process of gap repair or, alternatively, by single-strand annealing if the site of the break is flanked by directly repeated homologous sequences. We have shown previously (J. Fishman-Lobell and J. E. Haber, Science 258:480-484, 1992) that during the repair of an HO-induced DSB, the excision repair gene RAD1 is needed to remove regions of nonhomology from the DSB ends. In this report, we present evidence that among nine genes involved in nucleotide excision repair, only RAD1 and RAD10 are required for removal of nonhomologous sequences from the DSB ends. rad1 delta and rad10 delta mutants displayed a 20-fold reduction in the ability to execute both gap repair and single-strand annealing pathways of HO-induced recombination. Mutations in RAD2, RAD3, and RAD14 reduced HO-induced recombination by about twofold. We also show that RAD7 and RAD16, which are required to remove U...
Suppression of the Double-Strand-Break-Repair Defect of the Saccharomyces cerevisiae rad57 Mutant
Genetics, 2009
The Rad51 paralogs Rad55 and Rad57 form a heterodimer required to mediate the formation and/or stabilization of the Rad51 filament. To further characterize the function of Rad55-Rad57, we used a combination of rad57 partial suppressors to determine whether the DNA repair and recombination defects of the rad57 mutant could be completely suppressed. The combination of all suppressors, elevated temperature, srs2, rad51-I345T, and mating-type (MAT) heterozygosity resulted in almost complete suppression of the rad57 mutant defect in the recruitment of Rad51 to DNA-damaged sites, as well as survival in response to ionizing radiation and camptothecin. In a physical assay to monitor the kinetics of double-strand-break (DSB)-induced gene conversion, the rad57 mutant defect was effectively suppressed by srs2 and MAT heterozygosity, but these same suppressors failed to suppress the spontaneous recombination defect. Thus the Rad55-Rad57 heterodimer appears to have a unique function in spontaneo...
Molecular and cellular biology, 1997
During repair of a double-strand break (DSB) by gene conversion, one or both 3' ends of the DSB invade a homologous donor sequence and initiate new DNA synthesis. The use of the invading DNA strand as a primer for new DNA synthesis requires that any nonhomologous bases at the 3' end be removed. We have previously shown that removal of a 3' nonhomologous tail in Saccharomyces cerevisiae depends on the nucleotide excision repair endonuclease Rad1/Rad10, and also on the mismatch repair proteins Msh2 and Msh3. We now report that these four proteins are needed only when the nonhomologous ends of recombining DNA are 30 nucleotides (nt) long or longer. An additional protein, the helicase Srs2, is required for the RAD1-dependent removal of long 3' tails. We suggest that Srs2 acts to extend and stabilize the initial nascent joint between the invading single strand and its homolog. 3' tails shorter than 30 nt are removed by another mechanism that depends at least in part o...
Inaugural Article: Real-time analysis of double-strand DNA break repair by homologous recombination
Proceedings of The National Academy of Sciences, 2011
The ability to induce synchronously a single site-specific doublestrand break (DSB) in a budding yeast chromosome has made it possible to monitor the kinetics and genetic requirements of many molecular steps during DSB repair. Special attention has been paid to the switching of mating-type genes in Saccharomyces cerevisiae, a process initiated by the HO endonuclease by cleaving the MAT locus. A DSB in MATa is repaired by homologous recombinationspecifically, by gene conversion-using a heterochromatic donor, HMLα. Repair results in the replacement of the a-specific sequences (Ya) by Yα and switching from MATa to MATα. We report that MAT switching requires the DNA replication factor Dpb11, although it does not require the Cdc7-Dbf4 kinase or the Mcm and Cdc45 helicase components. Using Southern blot, PCR, and ChIP analysis of samples collected every 10 min, we extend previous studies of this process to identify the times for the loading of Rad51 recombinase protein onto the DSB ends at MAT, the subsequent strand invasion by the Rad51 nucleoprotein filament into the donor sequences, the initiation of new DNA synthesis, and the removal of the nonhomologous Y sequences. In addition we report evidence for the transient displacement of well-positioned nucleosomes in the HML donor locus during strand invasion.
… and cellular biology, 1994
In haploid rad52 Saccharomyces cerevisiae strains unable to undergo homologous recombination, a chromosomal double-strand break (DSB) can be repaired by imprecise rejoining of the broken chromosome ends. We have used two different strategies to generate broken chromosomes: (i) a site-specific DSB generated at the AMT locus by HO endonuclease cutting or (ii) a random DSB generated by mechanical rupture during mitotic segregation of a conditionally dicentric chromosome. Broken chromosomes were repaired by deletions that were highly variable in size, all of which removed more sequences than was required either to prevent subsequent HO cleavage or to eliminate a functional centromere, respectively. The junction of the deletions frequently occurred where complementary strands from the flanking DNA could anneal to form 1 to 5 bp, although 12% (4 of 34) of the events appear to have occurred by blunt-end ligation. These types of deletions are very similar to the junctions observed in the repair of DSBs by mammalian cells (D. B. Roth and J. H. Wilson, Mol. Cell. Biol. 6:4295-4304, 1986). When a high level of HO endonuclease, expressed in all phases of the cell cycle, was used to create DSBs, we also recovered a large class of very small (2or 3-bp) insertions in the HO cleavage site. These insertions appear to represent still another mechanism of DSB repair, apparently by annealing and ifiling in the overhanging 3' ends of the cleavage site. These types of events have also been well documented for vertebrate cells.