Dual Roles for DNA Polymerase η in Homologous DNA Recombination and Translesion DNA Synthesis

Kawamoto, Takuo; Araki, Koji; Sonoda, Eiichiro; Yamashita, Yukiko; Harada, Kouji H.; Kikuchi, Koji; Masutani, Chikahide; Hanaoka, Fumio; Nozaki, Kazuhiko; Hashimoto, Nobuo; Takeda, Shunichi

doi:10.1016/j.molcel.2005.10.016

Cited by 220 publications

(203 citation statements)

References 30 publications

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“…Only when this process creates sequence changes that eliminate the MluI recognition site do we identify them in our screen. Thus, the simple substitutions that we recover are probably generated during gene conversion by error-prone DNA synthesis, perhaps by DNA polymerase (42,43). We also found substitutions associated with some deletion products, particularly in lig-4 worms, so error-prone synthesis may be characteristic of the alternative end joining pathway as well (44).…”

Section: Products From Wtmentioning

confidence: 56%

Induction and repair of zinc-finger nuclease-targeted double-strand breaks in Caenorhabditis elegans somatic cells

Morton

Davis

Jørgensen

et al. 2006

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

169

124

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Zinc-finger nucleases are chimeric proteins consisting of engineered zinc-finger DNA-binding motifs attached to an endonuclease domain. These proteins can induce site-specific DNA double-strand breaks in genomic DNA, which are then substrates for cellular repair mechanisms. Here, we demonstrate that engineered zinc-finger nucleases function effectively in somatic cells of the nematode Caenorhabditis elegans. Although gene-conversion events were indistinguishable from uncut DNA in our assay, nonhomologous end joining resulted in mutations at the target site. A synthetic target on an extrachromosomal array was targeted with a previously characterized nuclease, and an endogenous genomic sequence was targeted with a pair of specifically designed nucleases. In both cases, Ϸ20% of the target sites were mutated after induction of the corresponding nucleases. Alterations in the extrachromosomal targets were largely products of end-filling and blunt ligation. By contrast, alterations in the chromosomal target were mostly deletions. We interpret these differences to reflect the abundance of homologous templates present in the extrachromosomal arrays versus the paucity of such templates for repair of chromosomal breaks. In addition, we find evidence for the involvement of error-prone DNA synthesis in both homologous and nonhomologous pathways of repair. DNA ligase IV is required for efficient end joining, particularly of blunt ends. In its absence, a secondary end-joining pathway relies more heavily on microhomologies in producing deletions.DNA repair ͉ gene targeting ͉ nematodes ͉ nonhomologous end joining T he ability to make targeted double-strand breaks in chromosomal DNA has several important uses. It allows the detailed study of DNA repair mechanisms; it leads to localized mutagenesis at the break site; and it enhances the efficiency of targeted gene replacement through homologous recombination. We have been exploring the capabilities of one class of targetable cleavage reagents, the zinc-finger nucleases (ZFNs).ZFNs are chimeric proteins composed of DNA-binding Cys 2 His 2 zinc fingers fused to the nonspecific nuclease domain of the restriction enzyme FokI (1). Each finger makes contact primarily with a separate DNA triplet (2, 3). Natural and artificial zinc fingers have been characterized that bind to all 5Ј-GNN-3Ј, many ANN and CNN, and some TNN triplets (4-7). Furthermore, the modular nature of the zinc fingers allows them to be joined in essentially arbitrary combinations. Typically, three zinc fingers are combined to bind to a specific 9-bp DNA sequence with the nanomolar affinity required to be biologically useful, but additional fingers can be incorporated to confer increased specificity (8-11). Zinc-finger fusions to various functional domains have been used to create artificial transcription factors and DNA-modifying proteins (12,13).When attached to the FokI nuclease domain, zinc fingers can direct cleavage to specific DNA sequences. The nuclease domain must dimerize to cleave DNA (14), and because the di...

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Section: Products From Wtmentioning

confidence: 56%

Induction and repair of zinc-finger nuclease-targeted double-strand breaks in Caenorhabditis elegans somatic cells

Morton

Davis

Jørgensen

et al. 2006

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

169

124

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“…In particular, they have also been implicated in the regulation of translesion polymerases in postreplication repair (16,17), but the function of these polymerases in other genetic processes in eukaryotes may also be regulated by different means, i.e., independently of the Rad6 pathway (18)(19)(20). In the present study, we show that the crucial initiator factor of the Rad6 pathway, Rad18, plays a role during somatic hypermutation in the DT40 B cell line.…”

mentioning

confidence: 48%

Involvement of Rad18 in somatic hypermutation

Brinckmann¹,

Ertongur²,

Jungnickel³

2006

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

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Somatic hypermutation of Ig genes is initiated by transcriptioncoupled cytidine deamination in Ig loci. Error-prone processing of the resultant DNA lesions is thought to cause extensive mutagenesis, but it is presently an enigma how and why error-prone rather than error-free repair pathways are recruited. During DNA replication, recruitment of error-prone translesion polymerases may be mediated by Rad6͞Rad18-mediated ubiquitination of proliferating cell nuclear antigen, a major switchboard controlling the fidelity of DNA lesion bypass in eukaryotes. By inactivation of Rad18 in the DT40 B cell line, we show that the Rad6 pathway is involved in somatic hypermutation in these cells. Our findings imply that targeted recruitment of mutagenic polymerases by the Rad6 pathway contributes to the complex process of somatic hypermutation and provide a framework for more detailed mechanistic studies of the mutagenesis phase of secondary Ig diversification.proliferating cell nuclear antigen ͉ ubiquitination ͉ Rad6 pathway G iven the many challenges that damage cellular DNA daily, the faithful maintenance of genetic information requires the interplay of multiple DNA repair pathways. In most cases, these mechanisms ensure restoration of the original DNA sequence, preventing mutations or aberrations that may lead to impairment of cellular function. In some instances, though, a certain imprecision may be tolerated or even favored by the cell to allow for survival in critical situations. DNA repair mechanisms that are inherently imprecise are the basis of the spontaneous mutability of all genomes and may be recruited and adapted for situations where high genetic variability is mandatory for survival.The adaptive immune system of vertebrates has been shaped in coevolution with pathogenic organisms of high genetic diversity and variability. The high diversity of the primary immune repertoire established during V(D)J recombination in B and T cells generates sufficient potential for recognition of any pathogen, but the affinity of binding is often not sufficient for effective neutralization. Therefore, a second wave of diversification during acute infections ensures that the binding affinity of the antibodies produced by B lymphocytes is fine-tuned to the task at hand. The underlying mechanism in humans is somatic hypermutation, which modifies the antigen binding region by targeted mutagenesis in the variable region of the Ig genes (1). An alternative diversification mechanism prevalent in chicken and some mammals, Ig gene conversion alters the same region by targeted homologous recombination with upstream Ig pseudogenes (2).Somatic hypermutation and Ig gene conversion are related processes (3) originating from the same initial DNA lesion. The transcription-coupled deamination of cytosines by activationinduced cytidine deaminase (AID) leads to uracil that may be processed to abasic sites or strand breaks by the excision repair pathway, i.e., uracil-N-glycosylase (4, 5). The resultant DNA lesions may be repaired by mutagenesis or reco...

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“…Recently, it has been proposed that, following DSB formation by a blocked replication fork at an ICL, TLS occurs as a necessary prelude for homologous recombination [45], and pol η could be the TLS polymerase involved in this model. In addition, pol η has also been reported to be involved in homologous recombination with a polymerase activity independent of its TLS functions [46,47] and could function in recombinational repair of DSB resulting from ICL.…”

Section: Discussionmentioning

confidence: 99%

DNA polymerase η reduces the γ-H2AX response to psoralen interstrand crosslinks in human cells

Mogi

Butcher

2008

Experimental Cell Research

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DNA interstrand crosslinks are processed by multiple mechanisms whose relationships to each other are unclear. Xeroderma pigmentosum-variant (XP-V) cells lacking DNA polymerase η are sensitive to psoralen photoadducts created under conditions favoring crosslink formation, suggesting a role for translesion synthesis in crosslink repair. Because crosslinks can lead to double strand breaks, we monitored phosphorylated H2AX (γ-H2AX), which is typically generated near double-strand breaks but also in response to single-stranded DNA, following psoralen photoadduct formation in XP-V fibroblasts to assess whether polymerase η is involved in processing crosslinks. In contrast to conditions favoring monoadducts, conditions favoring psoralen crosslinks induced γ-H2AX levels in both XP-V and nucleotide excision repair-deficient XP-A cells relative to control repair-proficient cells; ectopic expression of polymerase η in XP-V cells normalized the γ-H2AX response. In response to psoralen crosslinking, γ-H2AX as well as 53BP1 formed co-incident foci that were more numerous and intense in XP-V and XP-A cells than in controls. Psoralen photoadducts induced γ-H2AX throughout the cell cycle in XP-V cells. These results indicate that polymerase η is important in responding to psoralen crosslinks, and are consistent with a model in which nucleotide excision repair and polymerase η are involved in processing crosslinks and avoiding γ-H2AX associated with double strand breaks and single-stranded DNA in human cells.

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Dual Roles for DNA Polymerase η in Homologous DNA Recombination and Translesion DNA Synthesis

Cited by 220 publications

References 30 publications

Induction and repair of zinc-finger nuclease-targeted double-strand breaks in Caenorhabditis elegans somatic cells

Induction and repair of zinc-finger nuclease-targeted double-strand breaks in Caenorhabditis elegans somatic cells

Involvement of Rad18 in somatic hypermutation

DNA polymerase η reduces the γ-H2AX response to psoralen interstrand crosslinks in human cells

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