Role of PCNA-dependent stimulation of 3'-phosphodiesterase and 3'-5' exonuclease activities of human Ape2 in repair of oxidative DNA damage

Burkovics, Peter; Hajdú, Ildikó; Szukacsov, Valéria; Unk, Ildikó; Haracska, Lajos

doi:10.1093/nar/gkp357

Cited by 70 publications

(94 citation statements)

References 49 publications

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“…PCNA monoubiquitinated at lysine 164 is known to recruit the translesional polymerases Pol η and Rev1 (23), and SHM analyses in mice expressing a knock-in PCNA K164R mutation show a reduction in A:T mutations (49,50). The 3′ to 5′ exonuclease processivity of APE2 is also stimulated by PCNA (25) and could contribute to mutations by excising a few nucleotides at a SSB, exposing a short singlestrand patch 5′ to the AP site that could be filled in by Pol η, also resulting in mutations at A:T bp. This activity could explain the fact that during SHM, there are some A:T mutations in the absence of Msh2-Msh6, although Msh2-Msh6 is required for the vast majority of mutations at A:T bp (7).…”

Section: Discussionmentioning

confidence: 99%

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Differential expression of APE1 and APE2 in germinal centers promotes error-prone repair and A:T mutations during somatic hypermutation

Stavnezer

Linehan

Thompson

et al. 2014

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

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Somatic hypermutation (SHM) of antibody variable region genes is initiated in germinal center B cells during an immune response by activation-induced cytidine deaminase (AID), which converts cytosines to uracils. During accurate repair in nonmutating cells, uracil is excised by uracil DNA glycosylase (UNG), leaving abasic sites that are incised by AP endonuclease (APE) to create single-strand breaks, and the correct nucleotide is reinserted by DNA polymerase β. During SHM, for unknown reasons, repair is error prone. There are two APE homologs in mammals and, surprisingly, APE1, in contrast to its high expression in both resting and in vitro-activated splenic B cells, is expressed at very low levels in mouse germinal center B cells where SHM occurs, and APE1 haploinsufficiency has very little effect on SHM. In contrast, the less efficient homolog, APE2, is highly expressed and contributes not only to the frequency of mutations, but also to the generation of mutations at A:T base pair (bp), insertions, and deletions. In the absence of both UNG and APE2, mutations at A:T bp are dramatically reduced. Single-strand breaks generated by APE2 could provide entry points for exonuclease recruited by the mismatch repair proteins Msh2-Msh6, and the known association of APE2 with proliferating cell nuclear antigen could recruit translesion polymerases to create mutations at AIDinduced lesions and also at A:T bp. Our data provide new insight into error-prone repair of AID-induced lesions, which we propose is facilitated by down-regulation of APE1 and up-regulation of APE2 expression in germinal center B cells. D uring humoral immune responses, the recombined antibody variable [V(D)J] region genes undergo somatic hypermutation (SHM), which, after selection, greatly increases the affinity of antibodies for the activating antigen. This process occurs in germinal centers (GCs) in the spleen, lymph nodes, and Peyer's patches (PPs) and entirely depends on activation-induced cytidine deaminase (AID) (1, 2). AID initiates SHM by deamination of cytidine nucleotides in the variable region of antibody genes, converting the cytosine (dC) to uracil (dU) (1, 3, 4). Some AIDinduced dUs are excised by the ubiquitous enzyme uracil DNA glycosylase (UNG), resulting in abasic (AP) sites that can be recognized by apurinic/apyrimidinic endonuclease (APE) (4, 5). APE cleaves the DNA backbone at AP sites to form a singlestrand break (SSB) with a 3′ OH that can be extended by DNA polymerase (Pol) to replace the excised nucleotide (6). In most cells, DNA Pol β performs this extension with high fidelity, reinserting dC across from the template dG. In contrast, GC B cells undergoing SHM are rapidly proliferating, and some of the dUs are replicated over before they can be excised and are read as dT by replicative polymerases, resulting in dC to dT transition mutations. Unrepaired AP sites encountering replication lead to the nontemplated addition of any base opposite the site, causing transition and transversion mutations. However, it is not clear why dU...

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Section: Discussionmentioning

confidence: 99%

“…cell nuclear antigen (PCNA) (22), which can recruit error-prone translesion polymerases (23,24), and PCNA also increases the processivity of APE2 exonuclease in vitro (25). Both APE1 and APE2 are expressed in splenic B cells activated in culture (26).…”

mentioning

confidence: 99%

Differential expression of APE1 and APE2 in germinal centers promotes error-prone repair and A:T mutations during somatic hypermutation

Stavnezer

Linehan

Thompson

et al. 2014

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

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“…Instead, there is a second protein with homology to exonuclease III, termed APE2 (also known as APEX2) (71,208). The AP endonuclease and 3¢-damage excision activities of the human APE2 protein are generally weak, and, thus, its function as a DNA repair enzyme remains in question (18,19,70). It is not our intent to describe the current picture of APE2 in detail, but we point out that, while APE2-null mice exhibit growth retardation and dyshematopoiesis, APE2-deficient mouse embryonic stem cells or immortalized fibroblasts do not display increased sensitivity to several genotoxic agents, including hydrogen peroxide, bleomycin, or x-ray irradiation (86).…”

Section: And Wilsonmentioning

confidence: 99%

Human Apurinic/Apyrimidinic Endonuclease 1

2014

Antioxidants & Redox Signaling

224

221

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Significance: Human apurinic/apyrimidinic endonuclease 1 (APE1, also known as REF-1) was isolated based on its ability to cleave at AP sites in DNA or activate the DNA binding activity of certain transcription factors. We review herein topics related to this multi-functional DNA repair and stress-response protein. Recent Advances: APE1 displays homology to Escherichia coli exonuclease III and is a member of the divalent metal-dependent a/b fold-containing phosphoesterase superfamily of enzymes. APE1 has acquired distinct active site and loop elements that dictate substrate selectivity, and a unique N-terminus which at minimum imparts nuclear targeting and interaction specificity. Additional activities ascribed to APE1 include 3¢-5¢ exonuclease, 3¢-repair diesterase, nucleotide incision repair, damaged or site-specific RNA cleavage, and multiple transcription regulatory roles. Critical Issues: APE1 is essential for mouse embryogenesis and contributes to cell viability in a genetic background-dependent manner. Haploinsufficient APE1 +/ -mice exhibit reduced survival, increased cancer formation, and cellular/tissue hyper-sensitivity to oxidative stress, supporting the notion that impaired APE1 function associates with disease susceptibility. Although abnormal APE1 expression/localization has been seen in cancer and neuropathologies, and impaired-function variants have been described, a causal link between an APE1 defect and human disease remains elusive. Future Directions: Ongoing efforts aim at delineating the biological role(s) of the different APE1 activities, as well as the regulatory mechanisms for its intra-cellular distribution and participation in diverse molecular pathways. The determination of whether APE1 defects contribute to human disease, particularly pathologies that involve oxidative stress, and whether APE1 small-molecule regulators have clinical utility, is central to future investigations. Antioxid. Redox Signal. 20,

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“…APE1 (AP endonuclease 1) and APE2 (AP endonuclease 2) are the two characterized AP endonucleases (23,24). APE2, which has weak AP endonuclease activity and strong 3′-phosphodiesterase and 3′-5′ exonuclease activities, is a key player in PCNA-dependent repair of hydrogen peroxide (H 2 O 2 )-induced oxidative DNA damage (25)(26)(27). However, the biological significance of APE2 in the DNA damage response has not been elucidated.…”

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confidence: 99%

APE2 is required for ATR-Chk1 checkpoint activation in response to oxidative stress

Willis

Patel

Lentz

et al. 2013

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

149

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The base excision repair pathway is largely responsible for the repair of oxidative stress-induced DNA damage. However, it remains unclear how the DNA damage checkpoint is activated by oxidative stress at the molecular level. Here, we provide evidence showing that hydrogen peroxide (H 2 O 2 ) triggers checkpoint kinase 1 (Chk1) phosphorylation in an ATR [ataxia-telangiectasia mutated (ATM) and Rad3-related]-dependent but ATM-independent manner in Xenopus egg extracts. A base excision repair protein, Apurinic/apyrimidinic (AP) endonuclease 2 (APE2, APN2, or APEX2), is required for the generation of replication protein A (RPA)-bound single-stranded DNA, the recruitment of a checkpoint protein complex [ATR, ATR-interacting protein (ATRIP), and Rad9] to damage sites, and H 2 O 2 -induced Chk1 phosphorylation. A conserved proliferating cell nuclear antigen interaction protein box of APE2 is important for the recruitment of APE2 to H 2 O 2 -damaged chromatin. APE2 3′-phosphodiesterase and 3′-5′ exonuclease activity is essential for single-stranded DNA generation in the 3′-5′ direction from single-stranded breaks, referred to as single-stranded break end resection. In addition, APE2 associates with Chk1, and a serine residue (S86) in the Chk1-binding motif of APE2 is essential for Chk1 phosphorylation, indicating a Claspin-like but distinct role for APE2 in ATR-Chk1 signaling. Our data indicate that APE2 plays a vital and previously unexpected role in ATR-Chk1 checkpoint signaling in response to oxidative stress. Thus, our findings shed light on a distinct mechanism of how an ATR-Chk1-dependent DNA damage checkpoint is mediated by APE2 in the oxidative stress response. C ells are constantly challenged by exogenous and endogenous insults that threaten genomic integrity. Excess accumulation of reactive oxygen species leads to oxidative DNA damage, such as DNA strand breaks with 3′-modified termini, which is often the underlying pathology in a variety of diseases including neurodegenerative diseases and cancer (1-6). Cellular responses to DNA damage are mainly coordinated by two distinct DNA damage checkpoint signaling cascades: ATM (ataxia-telangiectasia mutated)-checkpoint kinase 2 (Chk2) and ATR (ATM and Rad3-related)-checkpoint kinase 1 (Chk1) pathways (7-10). ATM is activated by intermolecular autophosphorylation and dimer dissociation in response to double-stranded beaks (DSBs) (11-13). ATR is activated by primed single-stranded DNA (ssDNA) in response to a variety of DNA damage or replication stresses (14,15). Oxidative stress has been demonstrated to activate an ATMdependent DNA damage checkpoint (16-18). However, in previous studies, hyperoxic conditions resulted in the phosphorylation of Chk1 and p53 in an ATR-dependent but ATM-independent fashion (19). Furthermore, it remains unclear which specific DNA structures trigger checkpoint signaling during oxidative stress.To eliminate oxidative DNA damage, base excision repair (BER) has evolved as a major DNA damage repair mechanism (20). In the initial step of BER, o...

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Role of PCNA-dependent stimulation of 3'-phosphodiesterase and 3'-5' exonuclease activities of human Ape2 in repair of oxidative DNA damage

Cited by 70 publications

References 49 publications

Differential expression of APE1 and APE2 in germinal centers promotes error-prone repair and A:T mutations during somatic hypermutation

Differential expression of APE1 and APE2 in germinal centers promotes error-prone repair and A:T mutations during somatic hypermutation

Human Apurinic/Apyrimidinic Endonuclease 1

APE2 is required for ATR-Chk1 checkpoint activation in response to oxidative stress

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