Interference of DNA sequence divergence with precise recombinational DNA repair in mammalian cells.

Belmaaza, Abdellah; Milot, Eric; Villemure, Josée-France; Chartrand, Pascal

doi:10.1002/j.1460-2075.1994.tb06870.x

Cited by 15 publications

(13 citation statements)

References 34 publications

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“…The steps are invasion of the L1 donor sequence by only one side of the double-strand break, followed by DNA synthesis and then release of the invading end, and end-to-end joining with the other side of the DSB. This had also been observed in earlier studies on homologous recombination between extrachromosomal and endogenous chromosomal L1 elements in mouse cells (4,6).…”

Section: Vol 20 2000 Repair Of Dsb In a Chromosomal Line Element 55supporting

confidence: 81%

“…In this regard, it is interesting that the selection of partners was not based primarily on the degree of homology, since partners with higher (L1Md-A2 subfamily) and lower (T F family) homology appeared to have participated equally in the process. A lack of preference for highly homologous partners had also been seen for homologous recombination between extrachromosomal and chromosomal L1 elements (6,33). This could explain the genesis of mosaic lineages in L1 elements (40).…”

Section: Discussionmentioning

confidence: 98%

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A Double-Strand Break in a Chromosomal LINE Element Can Be Repaired by Gene Conversion with Various Endogenous LINE Elements in Mouse Cells

Tremblay

Jasin

Chartrand

2000

Molecular and Cellular Biology

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A double-strand break (DSB) in the mammalian genome has been shown to be a very potent signal for the cell to activate repair processes. Two different types of repair have been identified in mammalian cells. Broken ends can be rejoined with or without loss or addition of DNA or, alternatively, a homologous template can be used to repair the break. For most genomic sequences the latter event would involve allelic sequences present on the sister chromatid or homologous chromosome. However, since more than 30% of our genome consists of repetitive sequences, these would have the option of using nonallelic sequences for homologous repair. This could have an impact on the evolution of these sequences and of the genome itself. We have designed an assay to look at the repair of DSBs in LINE-1 (L1) elements which number 10 5 copies distributed throughout the genome of all mammals. We introduced into the genome of mouse epithelial cells an L1 element with an I-SceI endonuclease site. We induced DSBs at the I-SceI site and determined their mechanism of repair. We found that in over 95% of cases, the DSBs were repaired by an end-joining process. However, in almost 1% of cases, we found strong evidence for repair involving gene conversion with various endogenous L1 elements, with some being used preferentially. In particular, the T F family and the L1Md-A2 subfamily, which are the most active in retrotransposition, appeared to be contributing the most in this process. The degree of homology did not seem to be a determining factor in the selection of the endogenous elements used for repair but may be based instead on accessibility. Considering their abundance and dispersion, gene conversion between repetitive elements may be occurring frequently enough to be playing a role in their evolution.DNA double-strand breaks (DSBs) represent a threat to genomic integrity that have to be repaired efficiently or they will lead to serious consequences, such as programmed cell death (45). In mammalian cells, a single DSB can cause a cell cycle arrest (17). Mammalian DSB repair is a complex process that involves multiple proteins that vary depending on the cell cycle phase (16). Two main repair pathways are utilized (22). The first one involves the rejoining of the broken ends with or without the loss and/or addition of DNA. The second one involves homologous recombination with an intact copy of the broken DNA segment acting as a template. In most cases the homologous template could be the allelic copy present on the sister chromatid or homologous chromosome. However, since 30% of the genome is made of highly repetitive sequences, this raises the possibility that nonallelic homologous templates could be used for the repair of a DSB. Indeed, several groups have shown that a DSB occurring in a chromosomal construct containing tandemly repeated sequences could be repaired by homologous recombination at a frequency of as high as 30% (7,12,21,22,39,44). Also, it was shown that homologous sequences located at a nonallelic position on a distinct ...

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Section: Vol 20 2000 Repair Of Dsb In a Chromosomal Line Element 55supporting

confidence: 81%

Section: Discussionmentioning

confidence: 98%

A Double-Strand Break in a Chromosomal LINE Element Can Be Repaired by Gene Conversion with Various Endogenous LINE Elements in Mouse Cells

Tremblay

Jasin

Chartrand

2000

Molecular and Cellular Biology

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“…Thus, BLMdeficient cells may also accumulate chromosomal rearrangements during DSB repair through the coupling of gene conversion and NHEJ, a phenomenon that occurs with high frequency in cells with defects in the accurate termination of homologous recombination, such as BLM-, WRN-, XRCC3-, and MSH2-deficient cells (13,20,25,38 RAD51C, MSH2, or XRCC3, our results indicate that BRCA2 does not affect the processing of recombination intermediates towards gene conversion or against crossover, nor is it required for accurate termination of gene conversion. All gene conversion products in CAPAN-1 cells were flanked on both sides by homologous junctions; inaccurate termination of gene conversion is characterized by rearrangements at one homologous junction (25,39). In addition, unlike BLM-deficient cells, BRCA1/2-, ATM-, and FANC-deficient cells exhibit normal or decreased SCEs but increased frequency of spontaneous deletion and gene conversion events (refs.…”

Section: Discussionmentioning

confidence: 99%

BRCA2 Regulates Homologous Recombination in Response to DNA Damage: Implications for Genome Stability and Carcinogenesis

2005

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BRCA2 has been implicated in the maintenance of genome stability and RAD51-mediated homologous recombination repair of chromosomal double-strand breaks (DSBs), but its role in these processes is unclear. To gain more insight into its role in homologous recombination, we expressed wild-type BRCA2 in the well-characterized BRCA2-deficient human cell line CAPAN-1 containing, as homologous recombination substrates, either direct or inverted repeats of two inactive marker genes. Whereas direct repeats monitor a mixture of RAD51-dependent and RAD51-independent homologous recombination events, inverted repeats distinguish between these events by reporting RAD51-dependent homologous recombination, gene conversion, and crossover events only. At either repeats, BRCA2 decreases the rate and frequency of spontaneous homologous recombination, but following chromosomal DSBs, BRCA2 increases the frequency of homologous recombination. At direct repeats, BRCA2 suppresses both spontaneous gene conversion and deletions, which can arise either from crossover or RAD51-independent sister chromatid replication slippage (SCRS), but following chromosomal DSBs, BRCA2 highly promotes gene conversion with little effect on deletions. At inverted repeats, spontaneous or DSB-induced crossover events were scarce and BRCA2 does not suppress their formation. From these results, we conclude that (i) BRCA2 regulates RAD51 recombination in response to the type of DNA damage and (ii) BRCA2 suppresses SCRS, suggesting a role for BRCA2 in sister chromatids cohesion and/or alignment. Loss of such control in response to estrogeninduced DNA damage after BRCA2 inactivation may be a key initial event triggering genome instability and carcinogenesis. (Cancer Res 2005; 65(10): 4117-25)

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“…Homeologous recombination events have been recovered in several organisms, including yeast (2,12,15,16,18,31,32,34,35,40,43), bacteria (28, 36-39, 44, 45), and mammalian cells (3,53). When homeologous recombination is detected, it is typically much less frequent than is recombination between highly homologous sequences.…”

Section: ؊8mentioning

confidence: 99%

Fine-Resolution Analysis of Products of Intrachromosomal Homeologous Recombination in Mammalian Cells

Yang

Waldman

1997

Molecular and Cellular Biology

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Mouse Ltk؊ cell lines that contained a herpes simplex virus type 1 (HSV-1) thymidine kinase (tk) gene with a 16-bp insertion mutation linked to either a defective HSV-2 tk gene or a hybrid tk sequence comprised of HSV-1 and HSV-2 tk sequences were constructed. HSV-1 and HSV-2 tk genes have 81% nucleotide identity and hence are homeologous. Correction of the insertion mutant HSV-1 tk gene via recombination with the hybrid tk sequence required an exchange between homeologous tk sequences, although recombination could initiate within a region of significant sequence identity. Seven cell lines containing linked HSV-1 and HSV-1-HSV-2 hybrid tk sequences gave rise to tk ؉ segregants at an average rate of 10 ؊8 events per cell division. DNA sequencing revealed that each recombinant from these lines displayed an apparent gene conversion which involved an accurate transfer of an uninterrupted block of information between homeologous tk sequences. Conversion tract lengths ranged from 35 to >330 bp. In contrast, cell lines containing linked HSV-1 and HSV-2 tk sequences with no significant stretches of sequence identity had an overall rate of homeologous recombination of <10 ؊9. One such cell line produced homeologous recombinants at a rate of 10 ؊8. Strikingly, all homeologous recombinants from this latter cell line were due to crossovers between the HSV-1 and HSV-2 tk genes. Our results, which provide the first detailed analysis of homeologous recombination within a mammalian genome, suggest that rearrangements in mammalian genomes are regulated by the degree of sequence divergence located at the site of recombination initiation.Recombination between similar but imperfectly matched sequences is referred to as homeologous recombination. Homeologous recombination events have been recovered in several organisms, including yeast (2,12,15,16,18,31,32,34,35,40,43), bacteria (28, 36-39, 44, 45), and mammalian cells (3,53). When homeologous recombination is detected, it is typically much less frequent than is recombination between highly homologous sequences. Low rates for homeologous recombination may help to conserve genomic integrity by preventing undesirable rearrangements. On the other hand, when homeologous recombination does occur, it can potentially lead to novel genes and chromosomes and may play an important role in the evolution of genomes. For these reasons, it is of considerable interest to gain knowledge about such events as they occur in a variety of organisms. We previously investigated intrachromosomal homeologous recombination between a defective herpes simplex virus type 1 (HSV-1) thymidine kinase (tk) sequence and a closely linked HSV-2 tk sequence in the genome of mouse fibroblasts (52). HSV-1 and HSV-2 tk sequences have 81% sequence identity, with a 35-bp stretch of sequence identity being the longest (19, 49). The rate of intrachromosomal homeologous recombination between HSV-1 and HSV-2 tk sequences was reduced more than 1,000-fold compared with that of intrachromosomal recombination between nearly perfect...

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Interference of DNA sequence divergence with precise recombinational DNA repair in mammalian cells.

Cited by 15 publications

References 34 publications

A Double-Strand Break in a Chromosomal LINE Element Can Be Repaired by Gene Conversion with Various Endogenous LINE Elements in Mouse Cells

A Double-Strand Break in a Chromosomal LINE Element Can Be Repaired by Gene Conversion with Various Endogenous LINE Elements in Mouse Cells

BRCA2 Regulates Homologous Recombination in Response to DNA Damage: Implications for Genome Stability and Carcinogenesis

Fine-Resolution Analysis of Products of Intrachromosomal Homeologous Recombination in Mammalian Cells

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