DNA polymerases ν and θ are required for efficient immunoglobulin V gene diversification in chicken

Kohzaki, Masaoki; Nishihara, Kana; Hirota, Kouji; Sonoda, Eiichiro; Yoshimura, Masataka; Ekino, Shigeo; Butler, John E.; Watanabe, Masami; Halazonetis, Thanos D.; Takeda, Shunichi

doi:10.1083/jcb.200912012

Cited by 44 publications

(43 citation statements)

References 64 publications

(121 reference statements)

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“…Knockdown of POLQ is also reported to inhibit the viability of BRCA1 mutant cells [29]. A Polq mutant in chicken DT40 cells, was reported to have greatly reduced levels of homologous recombination repair of I-Sce -I-mediated DSBs [30]. However, such a role is not compatible with the other results that we summarize here.…”

Section: Functions Of Pol θcontrasting

confidence: 59%

DNA polymerase θ (POLQ), double-strand break repair, and cancer

2016

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DNA polymerase theta (pol θ) is encoded in the genomes of many eukaryotes, though not in fungi. Pol θ is encoded by the POLQ gene in mammalian cells. The C-terminal third of the protein is a family A DNA polymerase with additional insertion elements relative to prokaryotic homologs. The N-terminal third is a helicase-like domain with DNA-dependent ATPase activity. Pol θ is important in the repair of genomic double-strand breaks (DSBs) from many sources. These include breaks formed by ionizing radiation and topoisomerase inhibitors, breaks arising at stalled DNA replication forks, breaks introduced during diversification steps of the mammalian immune system, and DSB induced by CRISPR-Cas9. Pol θ participates in a route of DSB repair termed “alternative end-joining” (altEJ). AltEJ is independent of the DNA binding Ku protein complex and requires DNA end resection. Pol θ is able to mediate joining of two resected 3’ ends harboring DNA sequence microhomology. “Signatures” of Pol θ action during altEJ are the frequent utilization of longer microhomologies, and the insertion of additional sequences at joining sites. The mechanism of end-joining employs the ability of Pol θ to tightly grasp a 3’ terminus through unique contacts in the active site, allowing extension from minimally paired primers. Pol θ is involved in controlling the frequency of chromosome translocations and preserves genome integrity by limiting large deletions. It may also play a backup role in DNA base excision repair. POLQ is a member of a cluster of similarly upregulated genes that are strongly correlated with poor clinical outcome for breast cancer, ovarian cancer and other cancer types. Inhibition of pol θ is a compelling approach for combination therapy of radiosensitization.

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Section: Functions Of Pol θcontrasting

confidence: 59%

DNA polymerase θ (POLQ), double-strand break repair, and cancer

2016

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“…48 It is also plausible that gene conversion (GCV) could be implicated in the non-WRCH/DGYW mutations found in the zebrafish IgL. Given that diversification of immunoglobulin by gene conversion has only been shown to exist in chickens 49,50 and rabbits, 51 a comparative and evolutionary approach may prove necessary to elucidate additional currently unresolved aspects of SHM, CSR and GCV in vertebrates.…”

Section: Discussionmentioning

confidence: 99%

Targets of somatic hypermutation within immunoglobulin light chain genes in zebrafish

Marianes

Zimmerman

2010

Immunology

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Summary In mammals, somatic hypermutation (SHM) of immunoglobulin (Ig) genes is critical for the generation of high‐affinity antibodies and effective immune responses. Knowledge of sequence‐specific biases in the targeting of somatic mutations can be useful for studies aimed at understanding antibody repertoires produced in response to infections, B‐cell neoplasms, or autoimmune disease. To evaluate potential nucleotide targets of somatic mutation in zebrafish (Danio rerio), an enriched IgL cDNA library was constructed and > 250 randomly selected clones were sequenced and analysed. In total, 55 unique VJ‐C sequences were identified encoding a total of 125 mutations. Mutations were most prevalent in VL with a bias towards single base transitions and increased mutation in the complementarity‐determining regions (CDRs). Overall, mutations were overrepresented at WRCH/DGYW motifs suggestive of activation‐induced cytidine deaminase (AID) targeting which is common in mice and humans. In contrast to mammalian models, N and P addition was not observed and mutations at AID hotspots were largely restricted to palindromic WRCH/DGYW motifs. Mutability indexes for di‐ and trinucleotide combinations confirmed C/G targets within WRCH/DGYW motifs to be statistically significant mutational hotspots and showed trinucleotides ATC and ATG to be mutation coldspots. Additive mutations in VJ‐C sequences revealed patterns of clonal expansion consistent with affinity maturation responses seen in higher vertebrates. Taken together, the data reveal specific nucleotide targets of SHM in zebrafish and suggest that AID and affinity maturation contribute to antibody diversification in this emerging immunological model.

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“…Studies in Caenorhabditis elegans have also identified a role for POLQ-1 (a POLθ homolog) in ICL repair (Muzzini et al 2008). In addition to a role in ICL repair, POLθ also promotes base excision repair of oxidative damage (Yoshimura et al 2006) and somatic hypermutation (Masuda et al 2005; Seki et al 2005; Masuda et al 2007; Martomo et al 2008; Kohzaki et al 2010). …”

Section: Do Rev1 and Polζ Act Alone During Icl Repair?mentioning

confidence: 99%

REV1 and DNA polymerase zeta in DNA interstrand crosslink repair

Sharma

Canman

2012

Environ and Mol Mutagen

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DNA interstrand crosslinks (ICLs) are covalent linkages between two strands of DNA and their presence interfere with essential metabolic processes such as transcription and replication. These lesions are extremely toxic and their repair is essential for genome stability and cell survival. In this review, we will discuss how the removal of ICLs requires interplay between multiple genome maintenance pathways and can occur in the absence of replication (replication-independent ICL repair) or during S phase (replication-coupled ICL repair), the latter being the predominant pathway used in mammalian cells. It is now well recognized that translesion DNA synthesis (TLS), especially through the activities of REV1 and DNA polymerase zeta (Polζ), is necessary for both ICL repair pathways operating throughout the cell cycle. Recent studies suggest that the convergence of two replication forks upon an ICL initiates a cascade of events including unhooking of the lesion through the actions of structure-specific endonucleases thereby creating a DNA double stranded break (DSB). TLS across the unhooked lesion is necessary for restoring the sister chromatid prior to homologous recombination (HR) repair. Biochemical and genetic studies implicate REV1 and Polζ as being essential for performing lesion bypass across the unhooked crosslink and this step appears to be important for subsequent events to repair the intermediate DSB. The potential role of Fanconi anemia pathway in the regulation of REV1 and Polζ-dependent TLS and the involvement of additional polymerases, including DNA polymerases kappa, nu, and theta, in the repair of ICLs is also discussed in this review.

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DNA polymerases ν and θ are required for efficient immunoglobulin V gene diversification in chicken

Abstract: Polν and Polθ have specialized functions in immunoglobulin gene rearrangements and only contribute to DNA repair when other homologous recombination–related DNA polymerases are absent.

Cited by 44 publications

References 64 publications

DNA polymerase θ (POLQ), double-strand break repair, and cancer

DNA polymerase θ (POLQ), double-strand break repair, and cancer

Targets of somatic hypermutation within immunoglobulin light chain genes in zebrafish

REV1 and DNA polymerase zeta in DNA interstrand crosslink repair

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