Strategies to maintain the stability of the ribosomal RNA gene repeats  -Collaboration of recombination, cohesion, and condensation-

Kobayashi, Takehiko

doi:10.1266/ggs.81.155

Cited by 84 publications

(86 citation statements)

References 43 publications

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“…FAS/FAS, wild type; fas/ fas, mutant. Kobayashi, 2006;Labib and Hodgson, 2007;Tsang and Carr, 2008). Although the mechanism of rDNA copy number maintenance in plants has not been described so far, the replication fork barriers have been documented in plants (Hernandez et al, 1993;Lopez-Estrano et al, 1999), and the intergenic spacer of the 45S rDNA has been identified as a recombination hot spot (Urawa et al, 2001).…”

Section: Telomere Shortening and Chromosome-end Deprotectionmentioning

confidence: 99%

“…Although the mechanism of rDNA copy number maintenance in plants has not been described so far, the replication fork barriers have been documented in plants (Hernandez et al, 1993;Lopez-Estrano et al, 1999), and the intergenic spacer of the 45S rDNA has been identified as a recombination hot spot (Urawa et al, 2001). Whereas the yeast 5S rDNA is subjected to joint copy number regulation as a part of the 35S rDNA locus (Kobayashi, 2006), the separate localization and possibly different regulation of the 45S and the 5S rDNA loci in Arabidopsis may explain the selective loss of the 45S and not the 5S rDNA in the fas mutants (Figure 3; see Supplemental Figure 7 online). Since dysfunction of CAF1 in plants has been connected to increased numbers of DNA DSBs, increased level of HR, and upregulation of genes involved in HR (Endo et al, 2006;Kirik et al, 2006;Schonrock et al, 2006;Ramirez-Parra and Gutierrez, 2007), it is possible that disruption of a recombination-based maintenance equilibrium may lead to the 45S rDNA loss.…”

Section: Telomere Shortening and Chromosome-end Deprotectionmentioning

confidence: 99%

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Dysfunction of Chromatin Assembly Factor 1 Induces Shortening of Telomeres and Loss of 45S rDNA inArabidopsis thaliana

2010

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Chromatin Assembly Factor 1 (CAF1) is a three-subunit H3/H4 histone chaperone responsible for replication-dependent nucleosome assembly. It is composed of CAC 1-3 in yeast; p155, p60, and p48 in humans; and FASCIATA1 (FAS1), FAS2, and MULTICOPY SUPPRESSOR OF IRA1 in Arabidopsis thaliana. We report that disruption of CAF1 function by fas mutations in Arabidopsis results in telomere shortening and loss of 45S rDNA, while other repetitive sequences (5S rDNA, centromeric 180-bp repeat, CACTA, and Athila) are unaffected. Substantial telomere shortening occurs immediately after the loss of functional CAF1 and slows down at telomeres shortened to median lengths around 1 to 1.5 kb. The 45S rDNA loss is progressive, leaving 10 to 15% of the original number of repeats in the 5th generation of mutants affecting CAF1, but the level of the 45S rRNA transcripts is not altered in these mutants. Increasing severity of the fas phenotype is accompanied by accumulation of anaphase bridges, reduced viability, and plant sterility. Our results show that appropriate replicationdependent chromatin assembly is specifically required for stable maintenance of telomeres and 45S rDNA.

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Section: Telomere Shortening and Chromosome-end Deprotectionmentioning

confidence: 99%

Section: Telomere Shortening and Chromosome-end Deprotectionmentioning

confidence: 99%

Dysfunction of Chromatin Assembly Factor 1 Induces Shortening of Telomeres and Loss of 45S rDNA inArabidopsis thaliana

2010

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“…SSA is thought to be the predominant form of DSB repair within highly repetitive regions of the genome, such as the ribosomal DNA (Kobayashi 2006;Li et al 2008;George and Alani 2012), and limits unavoidable loss of genetic information to local deletions rather than large-scale rearrangements. It could also offset repeat expansions in these regions.…”

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confidence: 99%

A Delicate Balance Between Repair and Replication Factors Regulates Recombination Between Divergent DNA Sequences inSaccharomyces cerevisiae

Chakraborty¹,

George²,

Lyndaker

et al. 2015

Genetics

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Single-strand annealing (SSA) is an important homologous recombination mechanism that repairs DNA double strand breaks (DSBs) occurring between closely spaced repeat sequences. During SSA, the DSB is acted upon by exonucleases to reveal complementary sequences that anneal and are then repaired through tail clipping, DNA synthesis, and ligation steps. In baker's yeast, the Msh DNA mismatch recognition complex and the Sgs1 helicase act to suppress SSA between divergent sequences by binding to mismatches present in heteroduplex DNA intermediates and triggering a DNA unwinding mechanism known as heteroduplex rejection. Using baker's yeast as a model, we have identified new factors and regulatory steps in heteroduplex rejection during SSA. First we showed that Top3-Rmi1, a topoisomerase complex that interacts with Sgs1, is required for heteroduplex rejection. Second, we found that the replication processivity clamp proliferating cell nuclear antigen (PCNA) is dispensable for heteroduplex rejection, but is important for repairing mismatches formed during SSA. Third, we showed that modest overexpression of Msh6 results in a significant increase in heteroduplex rejection; this increase is due to a compromise in Msh2-Msh3 function required for the clipping of 39 tails. Thus 39 tail clipping during SSA is a critical regulatory step in the repair vs. rejection decision; rejection is favored before the 39 tails are clipped. Unexpectedly, Msh6 overexpression, through interactions with PCNA, disrupted heteroduplex rejection between divergent sequences in another recombination substrate. These observations illustrate the delicate balance that exists between repair and replication factors to optimize genome stability.

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“…However, the DNA sequence and structure itself also determines the fidelity of genome propagation, with each class of repeat DNA (i.e., ribosomal DNA, telomeres, trinucleotide repeats, and transposons) presenting unique challenges to the genome. There are pathways that predominate to ensure control of each repeat type [e.g., chromatin cohesion and transcriptional silencing are needed to stabilize ribosomal DNA repeat copy number whereas trinucleotide repeat array integrity depends on accurate DNA replication and mismatch repair (4,5)], but the precise interactions of repetitive DNA with the various DNA repair pathways remain unidentified.…”

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confidence: 99%

Retrotransposon overdose and genome integrity

Scheifele

Cost²,

Zupancic³

et al. 2009

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

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Yeast and mammalian genomes are replete with nearly identical copies of long dispersed repeats in the form of retrotransposons. Mechanisms clearly exist to maintain genome structure in the face of potential rearrangement between the dispersed repeats, but the nature of this machinery is poorly understood. Here we describe a series of distinct ''retrotransposon overdose'' (RO) lineages in which the number of Ty1 elements in the Saccharomyces cerevisiae genome has been increased by as much as 10 fold. Although these RO strains are remarkably normal in growth rate, they demonstrate an intrinsic supersensitivity to DNA-damaging agents. We describe the identification of mutants in the DNA replication pathway that enhance this RO-specific DNA damage supersensitivity by promoting ectopic recombination between Ty1 elements. Abrogation of normal DNA replication leads to rampant genome instability primarily in the form of chromosomal aberrations and confirms the central role of DNA replication accuracy in the stabilization of repetitive DNA.chromosome rearrangement ͉ genome instability ͉ Ty1 elements

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Strategies to maintain the stability of the ribosomal RNA gene repeats -Collaboration of recombination, cohesion, and condensation-

Cited by 84 publications

References 43 publications

Dysfunction of Chromatin Assembly Factor 1 Induces Shortening of Telomeres and Loss of 45S rDNA inArabidopsis thaliana

Dysfunction of Chromatin Assembly Factor 1 Induces Shortening of Telomeres and Loss of 45S rDNA inArabidopsis thaliana

A Delicate Balance Between Repair and Replication Factors Regulates Recombination Between Divergent DNA Sequences inSaccharomyces cerevisiae

Retrotransposon overdose and genome integrity

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