Timing of molecular events in meiosis in Saccharomyces cerevisiae: stable heteroduplex DNA is formed late in meiotic prophase

1993 ◽  
Vol 13 (1) ◽  
pp. 373-382 ◽  
Author(s):  
C Goyon ◽  
M Lichten

To better understand the means by which chromosomes pair and recombine during meiosis, we have determined the time of appearance of heteroduplex DNA relative to the times of appearance of double-strand DNA breaks and of mature recombined molecules. Site-specific double-strand breaks appeared early in meiosis and were formed and repaired with a timing consistent with a role for breaks as initiators of recombination. Heteroduplex-containing molecules appeared about 1 h after double-strand breaks and were followed shortly by crossover products and the first meiotic nuclear division. We conclude that parental chromosomes are stably joined in heteroduplex-containing structures late in meiotic prophase and that these structures are rapidly resolved to yield mature crossover products. If the chromosome pairing and synapsis observed earlier in meiotic prophase is mediated by formation of biparental DNA structures, these structures most likely either contain regions of non-Watson-Crick base pairs or contain regions of heteroduplex DNA that either are very short or dissociate during DNA purification. Two loci were examined in this study: the normal ARG4 locus, and an artificial locus consisting of an arg4-containing plasmid inserted at MAT. Remarkably, sequences in the ARG4 promoter that suffered double-strand cleavage at the normal ARG4 locus were not cut at significant levels when present at MAT::arg4. These results indicate that the formation of double-strand breaks during meiosis does not simply involve the specific recognition and cleavage of a short nucleotide sequence.

1993 ◽  
Vol 13 (1) ◽  
pp. 373-382 ◽  
Author(s):  
C Goyon ◽  
M Lichten

To better understand the means by which chromosomes pair and recombine during meiosis, we have determined the time of appearance of heteroduplex DNA relative to the times of appearance of double-strand DNA breaks and of mature recombined molecules. Site-specific double-strand breaks appeared early in meiosis and were formed and repaired with a timing consistent with a role for breaks as initiators of recombination. Heteroduplex-containing molecules appeared about 1 h after double-strand breaks and were followed shortly by crossover products and the first meiotic nuclear division. We conclude that parental chromosomes are stably joined in heteroduplex-containing structures late in meiotic prophase and that these structures are rapidly resolved to yield mature crossover products. If the chromosome pairing and synapsis observed earlier in meiotic prophase is mediated by formation of biparental DNA structures, these structures most likely either contain regions of non-Watson-Crick base pairs or contain regions of heteroduplex DNA that either are very short or dissociate during DNA purification. Two loci were examined in this study: the normal ARG4 locus, and an artificial locus consisting of an arg4-containing plasmid inserted at MAT. Remarkably, sequences in the ARG4 promoter that suffered double-strand cleavage at the normal ARG4 locus were not cut at significant levels when present at MAT::arg4. These results indicate that the formation of double-strand breaks during meiosis does not simply involve the specific recognition and cleavage of a short nucleotide sequence.


2009 ◽  
Vol 106 (37) ◽  
pp. 15762-15767 ◽  
Author(s):  
Samantha G. Zeitlin ◽  
Norman M. Baker ◽  
Brian R. Chapados ◽  
Evi Soutoglou ◽  
Jean Y. J. Wang ◽  
...  

The histone H3 variant CENP-A is required for epigenetic specification of centromere identity through a loading mechanism independent of DNA sequence. Using multiphoton absorption and DNA cleavage at unique sites by I-SceI endonuclease, we demonstrate that CENP-A is rapidly recruited to double-strand breaks in DNA, along with three components (CENP-N, CENP-T, and CENP-U) associated with CENP-A at centromeres. The centromere-targeting domain of CENP-A is both necessary and sufficient for recruitment to double-strand breaks. CENP-A accumulation at DNA breaks is enhanced by active non-homologous end-joining but does not require DNA-PKcs or Ligase IV, and is independent of H2AX. Thus, induction of a double-strand break is sufficient to recruit CENP-A in human and mouse cells. Finally, since cell survival after radiation-induced DNA damage correlates with CENP-A expression level, we propose that CENP-A may have a function in DNA repair.


Genetics ◽  
1995 ◽  
Vol 140 (1) ◽  
pp. 55-66 ◽  
Author(s):  
T C Wu ◽  
M Lichten

Abstract Double-strand DNA breaks (DSBs) initiate meiotic recombination in Saccharomyces cerevisiae. DSBs occur at sites that are hypersensitive in nuclease digests of chromatin, suggesting a role for chromatin structure in determining DSB location. We show here that the frequency of DSBs at a site is not determined simply by DNA sequence or by features of chromatin structure. An arg4-containing plasmid was inserted at several different locations in the yeast genome. Meiosis-induced DSBs occurred at similar sites in pBR322-derived portions of the construct at all insert loci, and the frequency of these breaks varied in a manner that mirrored the frequency of meiotic recombination in the arg4 portion of the insert. However, DSBs did not occur in the insert-borne arg4 gene at a site that is frequently broken at the normal ARG4 locus, even though the insert-borne arg4 gene and the normal ARG4 locus displayed similar DNase I hypersensitivity patterns. Deletions that removed active DSB sites from an insert at HIS4 restored breaks to the insert-borne arg4 gene and to a DSB site in flanking chromosomal sequences. We conclude that the frequency of DSB at a site can be affected by sequences several thousand nucleotides away and suggest that this is because of competition between DSB sites for locally limited factors.


1984 ◽  
Vol 4 (3) ◽  
pp. 387-398
Author(s):  
C T Wake ◽  
T Gudewicz ◽  
T Porter ◽  
A White ◽  
J H Wilson

Relatively little is known about the damage suffered by transfected DNA molecules during their journey from outside the cell into the nucleus. To follow selectively the minor subpopulation that completes this journey, we devised a genetic approach using simian virus 40 DNA transfected with DEAE-dextran. We investigated this active subpopulation in three ways: (i) by assaying reciprocal pairs of mutant linear dimers which differed only in the arrangement of two mutant genomes; (ii) by assaying a series of wild-type oligomers which ranged from 1.1 to 2.0 simian virus 40 genomes in length; and (iii) by assaying linear monomers of simian virus 40 which were cleaved within a nonessential region to leave either sticky, blunt, or mismatched ends. We conclude from these studies that transfected DNA molecules in the active subpopulation are moderately damaged by fragmentation and modification of ends. As a whole, the active subpopulation suffers about one break per 5 to 15 kilobases, and about 15 to 20% of the molecules have one or both ends modified. Our analysis of fragmentation is consistent with the random introduction of double-strand breaks, whose cause and exact nature are unknown. Our analysis of end modification indicated that the most prevalent form of damage involved deletion or addition of less than 25 base pairs. In addition we demonstrated directly that the efficiencies of joining sticky, blunt, or mismatched ends are identical, verifying the apparent ability of cells to join nearly any two DNA ends and suggesting that the efficiency of joining approaches 100%. The design of these experiments ensured that the detected damage preceded viral replication and thus should be common to all DNAs transfected with DEAE-dextran and not specific for viral DNA. These measurements of damage within transfected DNA have important consequences for studies of homologous and nonhomologous recombination in somatic cells as is discussed.


2017 ◽  
Vol 37 (24) ◽  
Author(s):  
Sucheta Arora ◽  
Rajashree A. Deshpande ◽  
Martin Budd ◽  
Judy Campbell ◽  
America Revere ◽  
...  

ABSTRACT Sae2 promotes the repair of DNA double-strand breaks in Saccharomyces cerevisiae. The role of Sae2 is linked to the Mre11/Rad50/Xrs2 (MRX) complex, which is important for the processing of DNA ends into single-stranded substrates for homologous recombination. Sae2 has intrinsic endonuclease activity, but the role of this activity has not been assessed independently from its functions in promoting Mre11 nuclease activity. Here we identify and characterize separation-of-function mutants that lack intrinsic nuclease activity or the ability to promote Mre11 endonucleolytic activity. We find that the ability of Sae2 to promote MRX nuclease functions is important for DNA damage survival, particularly in the absence of Dna2 nuclease activity. In contrast, Sae2 nuclease activity is essential for DNA repair when the Mre11 nuclease is compromised. Resection of DNA breaks is impaired when either Sae2 activity is blocked, suggesting roles for both Mre11 and Sae2 nuclease activities in promoting the processing of DNA ends in vivo. Finally, both activities of Sae2 are important for sporulation, indicating that the processing of meiotic breaks requires both Mre11 and Sae2 nuclease activities.


2016 ◽  
Author(s):  
Neeman Mohibullah ◽  
Scott Keeney

AbstractThe Spo11-generated double-strand breaks (DSBs) that initiate meiotic recombination are dangerous lesions that can disrupt genome integrity, so meiotic cells regulate their number, timing, and distribution. Here, we use Spo11-oligonucleotide complexes, a byproduct of DSB formation, to examine the contribution of the DNA damage-responsive kinase Tel1 (ortholog of mammalian ATM) to this regulation in Saccharomyces cerevisiae. A tel1Δ mutant had globally increased amounts of Spo11-oligonucleotide complexes and altered Spo11-oligonucleotide lengths, consistent with conserved roles for Tel1 in control of DSB number and processing. A kinase-dead tell mutation also increased Spo11-oligonucleotide levels, but mutating known Tel1 phosphotargets on Hop1 and Rec114 did not. Deep sequencing of Spo11 oligonucleotides from tel1Δ mutants demonstrated that Tel1 shapes the nonrandom DSB distribution in ways that are distinct but partially overlapping with previously described contributions of the recombination regulator Zip3. Finally, we uncover a context-dependent role for Tel1 in hotspot competition, in which an artificial DSB hotspot inhibits nearby hotspots. Evidence for Tel1-dependent competition involving strong natural hotspots is also provided.


Author(s):  
Eva Janisiw ◽  
Marilina Raices ◽  
Fabiola Balmir ◽  
Luis Paulin Paz ◽  
Antoine Baudrimont ◽  
...  

SummaryPoly(ADP-ribosyl)ation is a reversible post-translational modification synthetized by ADP-ribose transferases and removed by poly(ADP-ribose) glycohydrolase (PARG), which plays important roles in DNA damage repair. While well-studied in somatic tissues, much less is known about poly(ADP-ribosyl)ation in the germline, where DNA double-strand breaks are introduced by a regulated program and repaired by crossover recombination to establish a tether between homologous chromosomes. The interaction between the parental chromosomes is facilitated by meiotic specific adaptation of the chromosome axes and cohesins, and reinforced by the synaptonemal complex. Here, we uncover an unexpected role for PARG in promoting the induction of meiotic DNA breaks and their homologous recombination-mediated repair in Caenorhabditis elegans. PARG-1/PARG interacts with both axial and central elements of the synaptonemal complex, REC-8/Rec8 and the MRN/X complex. PARG-1 shapes the recombination landscape and reinforces the tightly regulated control of crossover numbers without requiring its catalytic activity. We unravel roles in regulating meiosis, beyond its enzymatic activity in poly(ADP-ribose) catabolism.


1985 ◽  
Vol 5 (12) ◽  
pp. 3331-3336
Author(s):  
K Y Song ◽  
L Chekuri ◽  
S Rauth ◽  
S Ehrlich ◽  
R Kucherlapati

We examined the effect of double-strand breaks on homologous recombination between two plasmids in human cells and in nuclear extracts prepared from human and rodent cells. Two pSV2neo plasmids containing nonreverting, nonoverlapping deletions were cotransfected into cells or incubated with cell extracts. Generation of intact neo genes was monitored by the ability of the DNA to confer G418r to cells or Neor to bacteria. We show that double-strand breaks at the sites of the deletions enhanced recombination frequency, whereas breaks outside the neo gene had no effect. Examination of the plasmids obtained from experiments involving the cell extracts revealed that gene conversion events play an important role in the generation of plasmids containing intact neo genes. Studies with plasmids carrying multiple polymorphic genetic markers revealed that markers located within 1,000 base pairs could be readily coconverted. The frequency of coconversion decreased with increasing distance between the markers. The plasmids we constructed along with the in vitro system should permit a detailed analysis of homologous recombinational events mediated by mammalian enzymes.


2018 ◽  
Vol 217 (7) ◽  
pp. 2299-2307 ◽  
Author(s):  
Vincent Amarh ◽  
Martin A. White ◽  
David R.F. Leach

Chromosomal replication is the major source of spontaneous DNA double-strand breaks (DSBs) in living cells. Repair of these DSBs is essential for cell viability, and accuracy of repair is critical to avoid chromosomal rearrangements. Repair of replication-dependent DSBs occurs primarily by homologous recombination with a sister chromosome. However, this reaction has never been visualized at a defined chromosomal locus, so little is known about its spatial or temporal dynamics. Repair of a replication-independent DSB generated in Escherichia coli by a rare-cutting endonuclease leads to the formation of a bundle of RecA filaments. In this study, we show that in contrast, repair of a replication-dependent DSB involves a transient RecA focus localized in the central region of the cell in which the DNA is replicated. The recombining loci remain centrally located with restricted movement before segregating with little extension to the period of postreplicative sister-chromosome cohesion. The spatial and temporal efficiency of this reaction is remarkable.


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