{"doi":"10.1074/jbc.m708345200","title":"Bcl2 Inhibits Abasic Site Repair by Down-regulating APE1 Endonuclease Activity","abstract":null,"journal":"Journal of Biological Chemistry","year":2008,"id":588570,"datarank":1.3701852828080843,"base_score":3.332204510175204,"endowment":3.332204510175204,"self_citation_contribution":0.49983067652628066,"citation_network_contribution":0.8703546062818035,"self_endowment_contribution":0.49983067652628066,"citer_contribution":0.8703546062818035,"corpus_percentile":null,"corpus_rank":null,"citation_count":27,"citer_count":23,"citers_with_citation_signal":20,"citers_with_endowment":20,"datacite_reuse_total":0,"is_dataset":false,"is_dataset_confidence":null,"is_data_producer":false,"deposit_databanks":null,"is_oa":false,"file_count":0,"downloads":0,"has_version_chain":false,"published_date":null,"fair_score":null,"fair_percentile":null,"algorithm_id":"datarank_citation_only_1hop_v6","ranking_scope":"data_only","authors":[{"id":544743,"name":"Fengqin Gao","orcid":null,"position":1,"is_corresponding":false},{"id":1505766,"name":"Yangde Zhang","orcid":null,"position":2,"is_corresponding":false},{"id":274498,"name":"Kun Wei","orcid":"0009-0007-1583-0196","position":3,"is_corresponding":false},{"id":1505767,"name":"Yunhai Liu","orcid":null,"position":4,"is_corresponding":false},{"id":315131,"name":"Xingming Deng","orcid":"0000-0003-0319-1511","position":5,"is_corresponding":false},{"id":1180985,"name":"Jinfeng Zhao","orcid":"0000-0003-3965-7125","position":0,"is_corresponding":false}],"reference_count":0,"raw_metadata":{"has_enrichment":true,"resolved":true,"title":"Bcl2 Inhibits Abasic Site Repair by Down-regulating APE1 Endonuclease Activity","abstract":"Bcl2 not only prolongs cell survival but also suppresses the repair of abasic (AP) sites of DNA lesions. Apurinic/apyrimidinic endonuclease 1 (APE1) plays a central role in the repair of AP sites via the base excision repair pathway. Here we found that Bcl2 down-regulates APE1 endonuclease activity in association with inhibition of AP site repair. Exposure of cells to nitrosamine 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone results in accumulation of Bcl2 in the nucleus and interaction with APE1, which requires all of the BH domains of Bcl2. Deletion of any of the BH domains from Bcl2 abrogates the ability of Bcl2 to interact with APE1 as well as the inhibitory effects of Bcl2 on APE1 activity and AP site repair. Overexpression of Bcl2 in cells reduces formation of the APE1·XRCC1 complex, and purified Bcl2 protein directly disrupts the APE1·XRCC1 complex with suppression of APE1 endonuclease activity in vitro. Importantly, specific knockdown of endogenous Bcl2 by RNA interference enhances APE1 endonuclease activity with accelerated AP site repair. Thus, Bcl2 inhibition of AP site repair may occur in a novel mechanism by down-regulating APE1 endonuclease activity, which may promote genetic instability and tumorigenesis. Bcl2 not only prolongs cell survival but also suppresses the repair of abasic (AP) sites of DNA lesions. Apurinic/apyrimidinic endonuclease 1 (APE1) plays a central role in the repair of AP sites via the base excision repair pathway. Here we found that Bcl2 down-regulates APE1 endonuclease activity in association with inhibition of AP site repair. Exposure of cells to nitrosamine 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone results in accumulation of Bcl2 in the nucleus and interaction with APE1, which requires all of the BH domains of Bcl2. Deletion of any of the BH domains from Bcl2 abrogates the ability of Bcl2 to interact with APE1 as well as the inhibitory effects of Bcl2 on APE1 activity and AP site repair. Overexpression of Bcl2 in cells reduces formation of the APE1·XRCC1 complex, and purified Bcl2 protein directly disrupts the APE1·XRCC1 complex with suppression of APE1 endonuclease activity in vitro. Importantly, specific knockdown of endogenous Bcl2 by RNA interference enhances APE1 endonuclease activity with accelerated AP site repair. Thus, Bcl2 inhibition of AP site repair may occur in a novel mechanism by down-regulating APE1 endonuclease activity, which may promote genetic instability and tumorigenesis. Apurinic/apyrimidinic (AP) 2The abbreviations used are:AP siteapurinic/apyrimidinic or abasic siteAPE1apurinic/apyrimidinic endonuclease 1NNKnitrosamine 4-(methylnitrosamino)-1-(3-pyridyl)-1y-butanoneBERbase excision repairBHBcl2 homologysiRNAsmall interfering RNAWTwild typePBSphosphate-buffered salineCHAPS3-[(3-cholamidopropyl)dimethylammonio]-1-propanesulfonic acidARPaldehyde reactive probe. or abasic sites are the most common form of DNA damage with about 20,000–50,000 sites produced in each cell/day (1Kelley M. Parsons S. Antioxid. Redox Signal. 2001; 3: 671-683Crossref PubMed Scopus (91) Google Scholar, 2Lau J. Weatherdon K. Skalski V. Hedley D. Br. J. Cancer. 2004; 91: 1166-1173Crossref PubMed Scopus (64) Google Scholar). AP sites can result from spontaneous and chemically initiated hydrolysis through various conditions, including ionizing radiation, UV irradiation, oxidative stress, and exposure to cigarette smoking (1Kelley M. Parsons S. Antioxid. Redox Signal. 2001; 3: 671-683Crossref PubMed Scopus (91) Google Scholar, 2Lau J. Weatherdon K. Skalski V. Hedley D. Br. J. Cancer. 2004; 91: 1166-1173Crossref PubMed Scopus (64) Google Scholar, 3Tell G. Damante G. Caldwell D. Kelley M. Antioxid. Redox Signal. 2005; 7: 367-384Crossref PubMed Scopus (327) Google Scholar, 4Jin Z. May W.S. Gao F. Flagg T. Deng X. J. Biol. Chem. 2006; 281: 14446-14456Abstract Full Text Full Text PDF PubMed Scopus (57) Google Scholar). Human apurinic/apyrimidinic endonuclease 1 (APE1) is a major constituent of the base excision repair (BER) pathway of AP sites of DNA lesions (3Tell G. Damante G. Caldwell D. Kelley M. Antioxid. Redox Signal. 2005; 7: 367-384Crossref PubMed Scopus (327) Google Scholar). Additionally, APE1 is also named as redox effector factor-1 (1Kelley M. Parsons S. Antioxid. Redox Signal. 2001; 3: 671-683Crossref PubMed Scopus (91) Google Scholar) because of its redox abilities on different redox-regulated transcription factors (3Tell G. Damante G. Caldwell D. Kelley M. Antioxid. Redox Signal. 2005; 7: 367-384Crossref PubMed Scopus (327) Google Scholar, 5Xanthoudakis S. Miao G. Curran T. Proc. Natl. Acad. Sci. U. S. A. 1994; 91: 23-27Crossref PubMed Scopus (320) Google Scholar). Two activities of this molecule are split into two functionally independent domains of the protein itself: the N terminus is principally devoted to the redox activity, whereas the C terminus exerts enzymatic activity on the repair of AP sites of DNA lesions (3Tell G. Damante G. Caldwell D. Kelley M. Antioxid. Redox Signal. 2005; 7: 367-384Crossref PubMed Scopus (327) Google Scholar, 5Xanthoudakis S. Miao G. Curran T. Proc. Natl. Acad. Sci. U. S. A. 1994; 91: 23-27Crossref PubMed Scopus (320) Google Scholar). APE1 specifically binds to abasic sites and cuts the 5′ phosphodiester bond with its endonuclease activity to produce a DNA primer with 3′ hydroxyl end, which is a required step in the BER repair pathway (3Tell G. Damante G. Caldwell D. Kelley M. Antioxid. Redox Signal. 2005; 7: 367-384Crossref PubMed Scopus (327) Google Scholar). Therefore, APE1 is an essential endonuclease and plays a central role in the repair of AP sites of DNA lesions. apurinic/apyrimidinic or abasic site apurinic/apyrimidinic endonuclease 1 nitrosamine 4-(methylnitrosamino)-1-(3-pyridyl)-1y-butanone base excision repair Bcl2 homology small interfering RNA wild type phosphate-buffered saline 3-[(3-cholamidopropyl)dimethylammonio]-1-propanesulfonic acid aldehyde reactive probe. Bcl2, a major cellular oncogenic protein, plays pivotal roles in enhancing cell survival, retarding G1/S cell cycle transition, and attenuating DNA repair (4Jin Z. May W.S. Gao F. Flagg T. Deng X. J. Biol. Chem. 2006; 281: 14446-14456Abstract Full Text Full Text PDF PubMed Scopus (57) Google Scholar, 6Deng X. Gao F. Flagg T. Anderson J. May W.S. Mol. Cell. Biol. 2006; 26: 4421-4434Crossref PubMed Scopus (116) Google Scholar, 7Deng X. Gao F. Flagg T. May W.S. Proc. Natl. Acad. Sci. U. S. A. 2004; 101: 153-158Crossref PubMed Scopus (133) Google Scholar). Because overexpression of Bcl2 results in lymphomagenesis in transgenic mice, this suggests that Bcl2, in addition to its survival activity, may also potentially have an oncogenic property (8Linette G.P. Hess J.L. Sentman C.L. Korsmeyer S.J. Blood. 1995; 86: 1255-1260Crossref PubMed Google Scholar). However, the mechanism(s) by which Bcl2 facilitates oncogenesis is not fully understood. The oncogenic effect of Bcl2 may result from its multiple cellular properties. Bcl2 was originally discovered as a gene product at the chromosomal breakpoint of t(14;18) (9Tsujimoto Y. Cossman J. Jaffe E. Croce C.M. Science. 1985; 229: 1390-1393Crossref PubMed Scopus (837) Google Scholar), which may play a role in genetic instability and tumor development by impeding DNA repair. It has been reported that Bcl2 can enhance benzene metabolite-induced DNA damage and mutagenesis in human promyelocytic HL60 cells (10Kuo M. Shiah S. Wang C. Chuang S. Mol. Pharmacol. 1999; 55: 894-901PubMed Google Scholar). Overexpression of Bcl2 not only attenuates the nucleotide excision repair capacity and DNA replication in UV-irradiated HL60 cells (11Liu Y. Naumovski L. Hanawalt P. Cancer Res. 1997; 57: 1650-1653PubMed Google Scholar) but also inhibits γ-ray-induced homologous recombination repair pathways (12Saintigny Y. Dumay A. Lambert S. Lopez B. EMBO J. 2001; 20: 2596-2607Crossref PubMed Scopus (82) Google Scholar). Bcl2 can also suppress DNA mismatch repair by inhibiting E2F transcriptional activity (13Youn C.K. Cho H. Kim S. Kim H. Kim M. Chang I. Lee J. Chung M. Hahm K. You H. Nat. Cell Biol. 2005; 7: 137-147Crossref PubMed Scopus (67) Google Scholar). Intriguingly, our recent findings reveal that Bcl2 suppression of DNA mismatch repair occur in a mechanism by directly regulating the heterodimeric hMSH2·hMSH6 complex, which leads to enhanced mutagenesis (14Hou Y. Gao F. Wang Q. Zhao J. Flagg T. Zhang Y. Deng X. J. Biol. Chem. 2007; 282: 9279-9287Abstract Full Text Full Text PDF PubMed Scopus (42) Google Scholar). Thus, the oncogenic activity of Bcl2 may result from its inhibitory effects on multiple DNA repair pathways. Nitrosamine 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK) is the most potent carcinogen contained in cigarette smoke that can induce cellular DNA damage including AP sites of DNA lesions (4Jin Z. May W.S. Gao F. Flagg T. Deng X. J. Biol. Chem. 2006; 281: 14446-14456Abstract Full Text Full Text PDF PubMed Scopus (57) Google Scholar, 15Jorquera R. Castonguay A. Schuller H. Carcinogenesis. 1994; 15: 389-394Crossref PubMed Scopus (29) Google Scholar, 16Mijal R. Thomson N. Fleischer N. Pauly G. Moschel R. Kanugula S. Fang Q. Pegg A. Peterson L. Chem. Res. Toxicol. 2004; 17: 424-434Crossref PubMed Scopus (58) Google Scholar). NNK-induced AP sites of DNA lesions, if unrepaired or repaired incorrectly, could be mutagenic, which may lead to mutations and chromosomal breaks with malignant transformation. We previously discovered that Bcl2 potently suppresses the repair of NNK-induced abasic sites of DNA lesions (4Jin Z. May W.S. Gao F. Flagg T. Deng X. J. Biol. Chem. 2006; 281: 14446-14456Abstract Full Text Full Text PDF PubMed Scopus (57) Google Scholar). However, the mechanism(s) is not fully understood. Here we found that Bcl2 not only directly interacts with APE1 but also inhibits its endonuclease activity, which leads to suppression of AP site repair. Materials—Bcl2, APE1, XRCC1, and tubulin antibodies were purchased from Santa Cruz Biotechnology (Santa Cruz, CA). NNK was purchased from Toronto Research Chemicals (Toronto, Canada). Purified recombinant WT, ΔBH1, ΔBH2, ΔBH3, and ΔBH4 Bcl2 mutant proteins were obtained from ProteinX Lab (San Diego, CA). Purified recombinant APE1 protein was purchased from Abnova Corporation (Taipei, Taiwan). Synthetic human Bcl2 siRNA (sense strand sequence, GGAUCCAGGAUAACGGAGGTT) was obtained from Santa Cruz Biotechnology. All of the reagents used were obtained from commercial sources unless otherwise stated. Generation of Various Bcl2 Deletion Mutants—To create ΔBH1, ΔBH2, ΔBH3, and ΔBH4 Bcl2 deletion mutants, the 5′ phosphorylated mutagenic primers for various precise deletion mutants were synthesized as follow: ΔBH1, 5′-GGA CGC TTT GCC ACG GTG GTG GAG GTG GAG AGC GTC AAC AGG GAG ATG-3′; ΔBH2, 5′-GAG TAC CTG AAC CGG CAT CTG CAC CGA CCT CTG TTT GAT TTC TCC TGG-3′; ΔBH3, 5′-GCG CTC AGC CCT GTG CCA CCT GTG GAC TTC GCA GAG ATG TCC AGT CAG-3′; ΔBH4, 5′-GGA AGG ATG GCG CAA GCC GGG AGA GCT GGA GAT GCG GAC GCG GCG CCC CTG-3′. The WT-Bcl2/pUC19 construct was used as the target plasmid that  a    site for   the   The   primer  5′-GAG   ATG   GTG  Various Bcl2 BH deletion mutants were  by  a mutagenesis    to the   and  by  of the  The  and various Bcl2 deletion mutants were   into the      Cell   and  human   cells were  as previously  (4Jin Z. May W.S. Gao F. Flagg T. Deng X. J. Biol. Chem. 2006; 281: 14446-14456Abstract Full Text Full Text PDF PubMed Scopus (57) Google Scholar). The  plasmid  each Bcl2 mutant  was  into  cells        or each of the Bcl2 deletion mutants were  in a      The   of  Bcl2 were  by       for each mutant    of  Bcl2 were  for    of Cell  were  with   and  in                1   1      and 1   with a  of    The cells were  by  and  at    for   at   The   was  as the  cell  and used for protein  or  as   X. Gao F. Flagg T. Anderson J. May W.S. Mol. Cell. Biol. 2006; 26: 4421-4434Crossref PubMed Scopus (116) Google Scholar).    was  as  previously (4Jin Z. May W.S. Gao F. Flagg T. Deng X. J. Biol. Chem. 2006; 281: 14446-14456Abstract Full Text Full Text PDF PubMed Scopus (57) Google Scholar).  the cells    were   with    and  in          1               The  cells were  with a    for   of   each at a  of  and   at    for   to  the  and   The  was  at   for   to   The  was  with    with       for   and   at    for   at   The    proteins was     the cells were  with   and  in   of                 with       The  were  on      of cells could be  by   The  were   at    at   for   The    was  with                      and   in   of  C                    and  at   for         at   the    was     from each  was  to  and  by    a Bcl2    cell were  with    with   and   for   and   with     for   at   The cells were  with a  Bcl2   for     the  were  with      antibodies for   The cells were  with   and   a     were  of each  AP   for APE1          a    at   was used as the APE1  as  (1Kelley M. Parsons S. Antioxid. Redox Signal. 2001; 3: 671-683Crossref PubMed Scopus (91) Google Scholar, 2Lau J. Weatherdon K. Skalski V. Hedley D. Br. J. Cancer. 2004; 91: 1166-1173Crossref PubMed Scopus (64) Google Scholar).    the  were purified  a   and   to a        from cells or purified APE1 protein were  in a       of     in             1          The  were  to  for   in a     and  by  an   of      and     of this   was  with a        APE1 endonuclease activity was  by  AP   in   DNA was purified  a DNA         The  of AP sites was   a DNA damage   site    to the        reactive     can  specifically with an aldehyde  that is the   form of the AP    DNA  AP sites with   AP sites are  with     an   of  all AP sites can be  to  AP    DNA and purified    DNA was  on a   with DNA    the  of AP sites in the  DNA was  by the   The  of the  was   a   with a     was    and the   the    of   Bcl2  is a  for down-regulating the  of a specific gene in  cells by  a  homologous    cells    of endogenous Bcl2 were  with Bcl2 siRNA        siRNA  to any  gene  was used as a   The  of Bcl2  were  by     of the  Bcl2 gene was  by at   independent   of  Bcl2   with  APE1   in Various Human  Cancer  is a  DNA repair  that   as an abasic endonuclease in the BER pathway (1Kelley M. Parsons S. Antioxid. Redox Signal. 2001; 3: 671-683Crossref PubMed Scopus (91) Google Scholar, 2Lau J. Weatherdon K. Skalski V. Hedley D. Br. J. Cancer. 2004; 91: 1166-1173Crossref PubMed Scopus (64) Google Scholar, 3Tell G. Damante G. Caldwell D. Kelley M. Antioxid. Redox Signal. 2005; 7: 367-384Crossref PubMed Scopus (327) Google Scholar). Intriguingly, APE1 is   in  small cell   and  cell   cells    that APE1 may play a role in regulating DNA repair in human    Bcl2, a major   oncogenic protein, is found to  with APE1 in  and  but not in    cells    We previously discovered that Bcl2 can suppress the repair of abasic sites of DNA lesions (4Jin Z. May W.S. Gao F. Flagg T. Deng X. J. Biol. Chem. 2006; 281: 14446-14456Abstract Full Text Full Text PDF PubMed Scopus (57) Google Scholar). However, the mechanism(s)      endogenous  of Bcl2 may potentially  APE1  AP endonuclease activity was  in various       AP site     was used as an APE1  as  (1Kelley M. Parsons S. Antioxid. Redox Signal. 2001; 3: 671-683Crossref PubMed Scopus (91) Google Scholar, 2Lau J. Weatherdon K. Skalski V. Hedley D. Br. J. Cancer. 2004; 91: 1166-1173Crossref PubMed Scopus (64) Google Scholar).   in   the  product  be  as a   that   the AP endonuclease repair    the    to  activity  be  as a   Thus, the AP endonuclease activity was  by the  of  product    AP site   were  with    from various human      of AP endonuclease activity    of    and   of    were  in   and  cells that    of endogenous Bcl2 as  with the  cell  that    of Bcl2    that Bcl2 may play a  role in regulating APE1 endonuclease  Overexpression of  Bcl2  APE1  and   AP   directly  effects of Bcl2 on APE1  and AP site  Bcl2 was   in  cells that  not    of endogenous Bcl2.   of the   was  into     with the    from     a  AP endonuclease activity in   cells    and    overexpression of Bcl2  the   from     and   findings  that Bcl2 suppresses APE1 endonuclease   results were obtained from  independent     of  Bcl2,  that  findings are  Because APE1 endonuclease activity is essential for AP site   inhibition of APE1 endonuclease activity may suppress AP site repair.   this    cells or   cells were  with NNK for   The cells were   and  with  cell   for various   to   AP sites of DNA lesions in  DNA were   a DNA damage   site   and   a   with a   as     The results reveal that NNK  enhances the AP sites of DNA lesions in    and   cells        of NNK from the   AP sites of DNA lesions in   cells are       that most AP sites are repaired in   cells      AP sites of DNA lesions are  in  cells as  with   cells       that overexpression of Bcl2 potently inhibits the repair of NNK-induced AP sites of DNA lesions.  results were obtained from  independent     of  Bcl2      purified APE1 protein can  the endonuclease activity in Bcl2        of purified APE1 protein were  to the    from   cells in   The results reveal that the addition of purified APE1 results in a   in the  of the     with a   of the       that the addition of  APE1 is  to  the endonuclease activity in   Exposure of  to the   NNK  Bcl2  and  with APE1 in  is   in the    with   in  and      D.  G.  C.  R. Korsmeyer S.     PubMed Scopus  Google Scholar,    A.  G.    B.  D. EMBO J.  15:  PubMed Scopus  Google Scholar).    that Bcl2 also  in the  and   the nucleus (4Jin Z. May W.S. Gao F. Flagg T. Deng X. J. Biol. Chem. 2006; 281: 14446-14456Abstract Full Text Full Text PDF PubMed Scopus (57) Google Scholar,  R.   H.  R.  S.    C.  J. Cell    7:  PubMed Scopus  Google Scholar,  C.  S.  G.    M. J.   1999;   PubMed Scopus  Google Scholar). We have previously  that the  Bcl2 has   activity but is  to suppress DNA repair (4Jin Z. May W.S. Gao F. Flagg T. Deng X. J. Biol. Chem. 2006; 281: 14446-14456Abstract Full Text Full Text PDF PubMed Scopus (57) Google Scholar).    Bcl2  APE1  DNA   cells    of endogenous Bcl2 and APE1 were  to NNK   for     of Bcl2 was   by    with our  findings (4Jin Z. May W.S. Gao F. Flagg T. Deng X. J. Biol. Chem. 2006; 281: 14446-14456Abstract Full Text Full Text PDF PubMed Scopus (57) Google Scholar), the  of Bcl2 is  in  and only a small  is  in the nucleus in   Intriguingly, Bcl2 is  in nucleus  exposure of cells to NNK for           was   to   and   The results reveal that  Bcl2  is enhanced         the   of  Bcl2 are   to the   as the      the       that   Bcl2   in a     the  of  Bcl2     in the        Thus,   Bcl2 may not result from a  from  into   effect on Bcl2  exposure of cells to NNK may occur through a transcriptional or      is required to  this    for a  interaction  Bcl2 and APE1 in  a  was      and an  APE1  The results reveal that NNK-induced DNA damage  Bcl2 to  with APE1 in a       Thus, Bcl2 suppression of APE1 activity and AP site repair may occur in a novel mechanism by a  interaction with  Bcl2   with APE1 via  BH  and Deletion of  of the BH  from Bcl2  in  of the  of Bcl2 to  APE1   and AP      homology in the BH domains including    and   A.  C.  Cell Biol.    Full Text Full Text PDF PubMed Scopus  Google Scholar).    Bcl2 directly binds to APE1 via its BH  purified recombinant APE1 protein   was  with purified recombinant WT, ΔBH1, ΔBH2, ΔBH3, or ΔBH4 Bcl2 deletion mutants    in     at   for   The  Bcl2 was  with an  APE1  The results  that APE1 is  to  with  but not with any of the ΔBH1, ΔBH2, ΔBH3, and ΔBH4 Bcl2 mutants      that all BH domains are essential for Bcl2 to interact with  Because  Bcl2 could not be  by the APE1  in the  of APE1      1    this suggests that the  of Bcl2 to APE1 is specific in this     Bcl2 protein directly  APE1 endonuclease activity in  a  AP site     was  with   APE1   in the  or  of purified recombinant  or each of the BH deletion Bcl2 mutant proteins    in the   as     The results reveal that purified APE1   the   into a       The addition of purified  Bcl2 protein  the   from   by APE1      that Bcl2 can directly  APE1 endonuclease activity in vitro. Intriguingly, all of the BH deletion Bcl2 mutant proteins  to suppress   of        that deletion of any of the BH domains abrogates the capacity of Bcl2 to  APE1 endonuclease   functionally  this in  APE1 endonuclease activity and AP sites of DNA lesions were  in cells   or each of the BH deletion  The results  that   of APE1 endonuclease activity and accelerated AP site repair were  in cells  each of the BH deletion mutants as  with   cells      the  that the  of Bcl2 to APE1 via its BH domains may be required for the effect of Bcl2 on APE1 activity and AP site repair. Overexpression of Bcl2 in    of the APE1·XRCC1  and Purified Bcl2   the APE1·XRCC1  in  with a   of APE1   in  has been reported that a  interaction  APE1 and   enhances APE1 endonuclease activity  A.  S.  I.  J. EMBO J. 2001; 20:  PubMed Scopus  Google Scholar). Because Bcl2 not only directly interacts with APE1 but also suppresses APE1 endonuclease activity in association with inhibition of AP site repair     Bcl2 may  the  interaction  APE1 and  via  to     association of APE1·XRCC1 was  in   cells and   cells in the  and  of  The results reveal that   of the APE1·XRCC1 complex were  in the  cells as  with   cells with or  NNK   that  of Bcl2 inhibits formation of the APE1·XRCC1 complex in cells       Bcl2 can directly  the APE1·XRCC1 complex in  the APE1·XRCC1 complex was  from   cells    of endogenous Bcl2  an APE1  The  complex was  with   of  recombinant Bcl2 at   for  to   and proteins  from the complex were  in the    at    for    Bcl2 directly disrupts the APE1·XRCC1 complex in  because the addition of purified Bcl2 results in   of   on  and   of   in the     the addition of     of  recombinant Bcl2 protein to the    from   cells results in a   in the  of the     with a   of the      Thus, in addition to a   to APE1,   of APE1 endonuclease activity may also  at  in  through  a  APE1·XRCC1    of Bcl2  by RNA   APE1   and  AP    a  role for Bcl2 in regulating APE1 activity and the repair of AP  a gene   was  to specifically  the endogenous Bcl2 from  cells that    of endogenous Bcl2.   have  that  of cells with siRNA           and a  of   only    effects  B. Nat.  2006; 3:  PubMed Scopus  Google Scholar). However, siRNA  of     not   effects  D.  L.  A.  P.  D.  S. Proc. Natl. Acad. Sci. U. S. A.    PubMed Scopus  Google Scholar).     we    of Bcl2 siRNA in the RNA interference  The results reveal that  of Bcl2 siRNA  reduces the   of endogenous Bcl2 by    in  cells    effect of siRNA on Bcl2  is  specific because the  siRNA has  effect   Importantly,  of Bcl2 from  cells    of endogenous Bcl2  APE1 endonuclease activity    of the    in association with accelerated AP site repair    and   findings    that   Bcl2 in cells is  to suppress AP site repair through a mechanism  the inhibition of APE1 endonuclease   of the most  lesions in DNA is the AP  which is the product of DNA  and the  DNA  in the  of     AP sites are potentially   mutagenic  L. Cell. 1985;   Full Text PDF PubMed Scopus  Google Scholar). APE1, the   in BER   the repair of AP sites  A.  S.  I.  J. EMBO J. 2001; 20:  PubMed Scopus  Google Scholar).    that Bcl2 can suppress the repair of various  of DNA  including AP sites of DNA lesions, in association with  genetic instability (4Jin Z. May W.S. Gao F. Flagg T. Deng X. J. Biol. Chem. 2006; 281: 14446-14456Abstract Full Text Full Text PDF PubMed Scopus (57) Google Scholar,  M. Shiah S. Wang C. Chuang S. Mol. Pharmacol. 1999; 55: 894-901PubMed Google Scholar,  Y. Naumovski L. Hanawalt P. Cancer Res. 1997; 57: 1650-1653PubMed Google Scholar,  Y. Dumay A. Lambert S. Lopez B. EMBO J. 2001; 20: 2596-2607Crossref PubMed Scopus (82) Google Scholar,  C.K. Cho H. Kim S. Kim H. Kim M. Chang I. Lee J. Chung M. Hahm K. You H. Nat. Cell Biol. 2005; 7: 137-147Crossref PubMed Scopus (67) Google Scholar,  C.  S.  A.     Google Scholar). However, the  mechanism(s) by which Bcl2  AP site repair   Here we found that overexpression of Bcl2 suppresses APE1 endonuclease activity with  AP site repair     of endogenous Bcl2 by RNA interference from  cells    of endogenous Bcl2 enhances APE1 endonuclease activity in association with accelerated AP site repair    findings  that the inhibitory effect of Bcl2 on AP site repair may  at  in  through down-regulating APE1 endonuclease  Bcl2 is   in   to  the      that Bcl2 has also been found in the  and   the nucleus (4Jin Z. May W.S. Gao F. Flagg T. Deng X. J. Biol. Chem. 2006; 281: 14446-14456Abstract Full Text Full Text PDF PubMed Scopus (57) Google Scholar,  R.   H.  R.  S.    C.  J. Cell    7:  PubMed Scopus  Google Scholar,  C.  S.  G.    M. J.   1999;   PubMed Scopus  Google Scholar). Intriguingly, the  Bcl2  not have   but  has ability to  DNA repair (4Jin Z. May W.S. Gao F. Flagg T. Deng X. J. Biol. Chem. 2006; 281: 14446-14456Abstract Full Text Full Text PDF PubMed Scopus (57) Google Scholar). APE1 is   in the  but  APE1 can also be  in  cell  (3Tell G. Damante G. Caldwell D. Kelley M. Antioxid. Redox Signal. 2005; 7: 367-384Crossref PubMed Scopus (327) Google Scholar). Here we found that NNK-induced DNA damage  can  Bcl2 accumulation in  which  interacts with APE1    may be a  mechanism by which Bcl2 down-regulates APE1 activity with suppression of AP site DNA repair. Bcl2    homology in   the BH domains    and   A.  C.  Cell Biol.    Full Text Full Text PDF PubMed Scopus  Google Scholar).   with Bcl2 deletion mutants reveal that APE1 directly interacts with Bcl2 and that all of the BH domains in Bcl2 are required for this interaction    and  Because the   and  domains form the    of Bcl2  M.  J.  D. Cell   2004;   PubMed Scopus  Google Scholar), our findings  that in addition to the   the  of the    of Bcl2 is also  for Bcl2 to  with   deletion of any of the BH domains  the capacity of Bcl2 to suppress APE1 endonuclease activity as well as AP site repair    that the    is required for the effects of Bcl2 on APE1 and AP site repair.   as  a  and a  of the different activities  in BER  a   the  and   of the AP site repair  Intriguingly,  not only  interacts with APE1 but also potently  its enzymatic activity  A.  S.  I.  J. EMBO J. 2001; 20:  PubMed Scopus  Google Scholar). Because overexpression of Bcl2 in cells or the addition of purified Bcl2 to the APE1·XRCC1 complex directly disrupts APE1·XRCC1 association   this  the  that the inhibitory effect of Bcl2 on APE1  may result from its   to APE1    of the APE1·XRCC1    our findings have  a novel  mechanism by which Bcl2 suppresses AP site repair through inhibition of APE1 endonuclease  NNK-induced AP sites of DNA lesions  Bcl2 accumulation in nucleus and interaction with APE1 via its BH   to  APE1 activity and  of AP site repair. 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