Repeat expansion by homologous recombination in the mouse germ line at palindromic sequences

Zhou, Zhi-Hong; Akgün, Ercan; Jasin, Maria

doi:10.1073/pnas.151008498

Cited by 49 publications

(31 citation statements)

References 39 publications

(39 reference statements)

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“…Indeed, amplification of sequences that initiate as palindromes has been documented (Zhou et al 2001;Lobachev et al 2002;Tanaka et al 2002). We suggest that it is the modulation of the MRX/N nuclease activity by a factor like Sae2p that drives amplification.…”

Section: Mechanism Of Palindrome Formation Genes and Development 1395mentioning

confidence: 79%

A mechanism of palindromic gene amplification in Saccharomyces cerevisiae

Rattray¹,

Shafer²,

Neelam³

et al. 2005

Genes Dev.

113

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Selective gene amplification is associated with normal development, neoplasia, and drug resistance. One class of amplification events results in large arrays of inverted repeats that are often complex in structure, thus providing little information about their genesis. We made a recombination substrate in Saccharomyces cerevisiae that frequently generates palindromic duplications to repair a site-specific double-strand break in strains deleted for the SAE2 gene. The resulting palindromes are stable in sae2⌬ cells, but unstable in wild-type cells. We previously proposed that the palindromes are formed by invasion and break-induced replication, followed by an unknown end joining mechanism. Here we demonstrate that palindrome formation can occur in the absence of RAD50, YKU70, and LIG4, indicating that palindrome formation defines a new class of nonhomologous end joining events. Sequence data from 24 independent palindromic duplication junctions suggest that the duplication mechanism utilizes extremely short (4-6 bp), closely spaced (2-9 bp), inverted repeats to prime DNA synthesis via an intramolecular foldback of a 3 end. In view of our data, we present a foldback priming model for how a single copy sequence is duplicated to generate a palindrome.[Keywords: DNA palindrome; gene amplification; MR complex; SAE2; Saccharomyces cerevisiae; BFB] Supplemental material is available at http://www.genesdev.org.

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Section: Mechanism Of Palindrome Formation Genes and Development 1395mentioning

confidence: 79%

A mechanism of palindromic gene amplification in Saccharomyces cerevisiae

Rattray¹,

Shafer²,

Neelam³

et al. 2005

Genes Dev.

113

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“…However, such studies are hampered by the fact that the locus of integration and the arrangement of the integrated DNA drastically influence the rate of recombination (42,(53)(54)(55). To overcome these problems, researchers have targeted homologous recombination substrates to specific loci (e.g., refs.…”

Section: Discussionmentioning

confidence: 99%

Spontaneous mitotic homologous recombination at an enhanced yellow fluorescent protein (EYFP) cDNA direct repeat in transgenic mice

Hendricks

Almeida²,

Stitt³

et al. 2003

Proc. Natl. Acad. Sci. U.S.A.

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A transgenic mouse has been created that provides a powerful tool for revealing genetic and environmental factors that modulate mitotic homologous recombination. The fluorescent yellow directrepeat (FYDR) mice described here carry two different copies of expression cassettes for truncated coding sequences of the enhanced yellow fluorescent protein (EYFP), arranged in tandem. Homologous recombination between these repeated elements can restore full-length EYFP coding sequence to yield a fluorescent phenotype, and the resulting fluorescent recombinant cells are rapidly quantifiable by flow cytometry. Analysis of genomic DNA from recombined FYDR cells shows that this mouse model detects gene conversions, and based on the arrangement of the integrated recombination substrate, unequal sister-chromatid exchanges and repair of collapsed replication forks are also expected to reconstitute EYFP coding sequence. The rate of spontaneous recombination in primary fibroblasts derived from adult ear tissue is 1.3 ؎ 0.1 per 10 6 cell divisions. Interestingly, the rate is Ϸ10-fold greater in fibroblasts derived from embryonic tissue. We observe an Ϸ15-fold increase in the frequency of recombinant cells in cultures of ear fibroblasts when exposed to mitomycin C, which is consistent with the ability of interstrand crosslinks to induce homologous recombination. In addition to studies of recombination in cultured primary cells, the frequency of recombinant cells present in skin was also measured by direct analysis of disaggregated cells. Thus, the FYDR mouse model can be used for studies of mitotic homologous recombination both in vitro and in vivo.H uman cells incur Ϸ10 6 base lesions per day (1), many of which inhibit DNA replication and͞or induce DNA strand breaks. Homology-directed repair provides an important strategy for preventing toxicity caused by such DNA lesions. More specifically, when the replication machinery stalls, recombination between sister chromatids can replace the damaged template with an undamaged copy (2). In addition, should a replication fork collapse to form a double-strand break (e.g., because of an encounter with a single-strand break in the template DNA), the fork can be repaired by homology-directed reinsertion of the broken end (3-5). Thus, the frequency of recombination reflects the levels of certain types of DNA damage.Repair and lesion-avoidance pathways that involve homology searching are integral to DNA replication (3-7). It is estimated that Ϸ10 double-strand breaks are formed each time the mammalian genome is replicated (3), and proteins that are essential for homologous recombination (e.g., Rad51) are also essential for life (8-10). Most of the time, sequences are aligned perfectly, and flanking sequences are not exchanged. However, misalignments may result in deletions, and exchanges between homologous chromosomes may lead to loss of heterozygosity, events that are known to promote cancer (11)(12)(13)(14).A useful approach to studying recombination is to engineer two mutant expression cassett...

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“…As reported by several groups, once this type of alteration occurs, very little further rearrangement is observed (1,4,10,22,39). However, for all of the transgenic studies, it was unknown whether or not the germ line-introduced palindromes were in fact truly palindromic.…”

mentioning

confidence: 90%

“…On the one hand, key processes can be positively affected by lineform-to-cruciform transitions, as studies of nearly palindromic inverted repeats contained in replication origins or transcriptional control regions have begun to demonstrate (11,14,16,38). On the other hand, palindromes have been implicated in various kinds of illegitimate genome rearrangements in mammalian cells, including gene amplification (12,32), repeat expansion (39), chromosomal translocations (7,17), and gross chromosomal deletions (9,28).…”

mentioning

confidence: 99%

Rapid, Stabilizing Palindrome Rearrangements in Somatic Cells by the Center-Break Mechanism

Cunningham

Coté

Cam-Ozdemir

et al. 2003

Molecular and Cellular Biology

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DNA palindromes are associated with rearrangement in a variety of organisms. A unique opportunity to examine the impact of a long palindrome in mammals is afforded by the Line 78 strain of mice. Previously it was found that the transgene in Line 78 is likely to be palindromic and that the symmetry of the transgene was responsible for a high level of germ line instability. Here we prove that Line 78 mice harbor a true 15.4-kb palindrome, and through the establishment of cell lines from Line 78 mice we have shown that the palindrome rearranges at the impressive rate of about 0.5% per population doubling. The rearrangements observed to arise from rapid palindrome modification are consistent with a center-break mechanism where double-strand breaks, created through hairpin nicking of an extruded cruciform, are imprecisely rejoined, thus introducing deletions at the palindrome center. Significantly, palindrome rearrangements in somatic tissue culture cells almost completely mirrored the structures generated in vivo in the mouse germ line. The close correspondence between germ line and somatic events indicates the possibility that center-break modification of palindromes is an important mechanism for preventing mutation in both contexts. Permanent cell lines carrying a verified palindrome provide an essential tool for future mechanistic analyses into the consequences of palindromy in the mammalian genome.

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Repeat expansion by homologous recombination in the mouse germ line at palindromic sequences

Cited by 49 publications

References 39 publications

A mechanism of palindromic gene amplification in Saccharomyces cerevisiae

A mechanism of palindromic gene amplification in Saccharomyces cerevisiae

Spontaneous mitotic homologous recombination at an enhanced yellow fluorescent protein (EYFP) cDNA direct repeat in transgenic mice

Rapid, Stabilizing Palindrome Rearrangements in Somatic Cells by the Center-Break Mechanism

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