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TopBP1, a multiple-BRCT-containing protein, plays diverse functions in DNA metabolism including DNA replication, DNA damage response and transcriptional regulation. The cytoplasmic localization of TopBP1 has been found to be associated with breast cancer susceptibility in clinical studies, suggesting the biological significance of TopBP1's sub-cellular localization. However, it remains elusive how TopBP1 is shuttled into nucleus and recruited to chromatin under normal or stressful conditions. Taking advantage of Xenopus egg extract, we identified Importin β as a new interacting protein of the TopBP1 C-terminus. We verified the TopBP1-Importin β association via GST pulldown and coimmunoprecipitation assays. We then demonstrated that TopBP1's C-terminal motif (designated as CTM, 23 amino acids) containing a putative NLS (nuclear localization signal) was required for Importin β interaction and that CT100 of Importin β (100 amino acids of extreme C-terminus of Importin β) was required for TopBP1 interaction. Further structure-function analysis reveals that the CTM of TopBP1 is essential for TopBP1's nuclear import and subsequent chromatin recruitment, thereby playing important roles in DNA replication and mitomycin C (MMC)-induced Chk1 phosphorylation. In addition, Importin β-specific inhibitor importazole inhibits TopBP1's nuclear import and the MMC-induced Chk1 phosphorylation. With ongoing DNA replication, the Importin β-dependent nuclear import of TopBP1 was indeed required for the MMC-induced Chk1 phosphorylation. Our data also suggest that checkpoint activation requires more TopBP1 than DNA replication does. The requirement of TopBP1's CTM motif for ATR-Chk1 checkpoint can be bypassed in a nucleus-free AT70 system. Taken together, our findings suggest that the CTM motif-mediated TopBP1 shuttling into nucleus via Importin β plays an important role in the ATR-Chk1 checkpoint signaling in Xenopus egg extracts.
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Bartkova,
DNA damage response as a candidate anti-cancer barrier in early human tumorigenesis.
2005, Pubmed
Bartkova,
DNA damage response as a candidate anti-cancer barrier in early human tumorigenesis.
2005,
Pubmed
Branzei,
Maintaining genome stability at the replication fork.
2010,
Pubmed
Byun,
Functional uncoupling of MCM helicase and DNA polymerase activities activates the ATR-dependent checkpoint.
2005,
Pubmed
,
Xenbase
Chen,
Chk1 in the DNA damage response: conserved roles from yeasts to mammals.
2004,
Pubmed
Choi,
Reconstitution of RPA-covered single-stranded DNA-activated ATR-Chk1 signaling.
2010,
Pubmed
Chook,
Nuclear import by karyopherin-βs: recognition and inhibition.
2011,
Pubmed
Ciccia,
The DNA damage response: making it safe to play with knives.
2010,
Pubmed
Cimprich,
ATR: an essential regulator of genome integrity.
2008,
Pubmed
Cingolani,
Structure of importin-beta bound to the IBB domain of importin-alpha.
1999,
Pubmed
Cortez,
ATR and ATRIP: partners in checkpoint signaling.
2001,
Pubmed
Cuadrado,
ATM regulates ATR chromatin loading in response to DNA double-strand breaks.
2006,
Pubmed
Delacroix,
The Rad9-Hus1-Rad1 (9-1-1) clamp activates checkpoint signaling via TopBP1.
2007,
Pubmed
Delmar,
Xenopus importin beta validates human importin beta as a cell cycle negative regulator.
2008,
Pubmed
,
Xenbase
Duursma,
A role for the MRN complex in ATR activation via TOPBP1 recruitment.
2013,
Pubmed
,
Xenbase
Forma,
Expression of TopBP1 in hereditary breast cancer.
2012,
Pubmed
Garcia,
Identification and functional analysis of TopBP1 and its homologs.
2005,
Pubmed
Giannattasio,
Exo1 competes with repair synthesis, converts NER intermediates to long ssDNA gaps, and promotes checkpoint activation.
2010,
Pubmed
Going,
Aberrant expression of TopBP1 in breast cancer.
2007,
Pubmed
Gong,
BACH1/FANCJ acts with TopBP1 and participates early in DNA replication checkpoint control.
2010,
Pubmed
Guo,
Requirement for Atr in phosphorylation of Chk1 and cell cycle regulation in response to DNA replication blocks and UV-damaged DNA in Xenopus egg extracts.
2000,
Pubmed
,
Xenbase
Hanahan,
Hallmarks of cancer: the next generation.
2011,
Pubmed
Harel,
Importin beta: conducting a much larger cellular symphony.
2004,
Pubmed
Harrison,
Surviving the breakup: the DNA damage checkpoint.
2006,
Pubmed
Hashimoto,
The phosphorylated C-terminal domain of Xenopus Cut5 directly mediates ATR-dependent activation of Chk1.
2006,
Pubmed
,
Xenbase
Hashimoto,
Xenopus Cut5 is essential for a CDK-dependent process in the initiation of DNA replication.
2003,
Pubmed
,
Xenbase
Herold,
Miz1 and HectH9 regulate the stability of the checkpoint protein, TopBP1.
2008,
Pubmed
Hirai,
A role of the C-terminal region of human Rad9 (hRad9) in nuclear transport of the hRad9 checkpoint complex.
2002,
Pubmed
Honda,
Cooperation of HECT-domain ubiquitin ligase hHYD and DNA topoisomerase II-binding protein for DNA damage response.
2002,
Pubmed
Jackson,
The DNA-damage response in human biology and disease.
2009,
Pubmed
Jazayeri,
ATM- and cell cycle-dependent regulation of ATR in response to DNA double-strand breaks.
2006,
Pubmed
Kadir,
Localization of the Drosophila Rad9 protein to the nuclear membrane is regulated by the C-terminal region and is affected in the meiotic checkpoint.
2012,
Pubmed
Karppinen,
Identification of a common polymorphism in the TopBP1 gene associated with hereditary susceptibility to breast and ovarian cancer.
2006,
Pubmed
Kumagai,
Treslin collaborates with TopBP1 in triggering the initiation of DNA replication.
2010,
Pubmed
,
Xenbase
Kumagai,
TopBP1 activates the ATR-ATRIP complex.
2006,
Pubmed
,
Xenbase
Kumagai,
Claspin, a novel protein required for the activation of Chk1 during a DNA replication checkpoint response in Xenopus egg extracts.
2000,
Pubmed
,
Xenbase
Kutay,
Dominant-negative mutants of importin-beta block multiple pathways of import and export through the nuclear pore complex.
1997,
Pubmed
,
Xenbase
Lee,
The Rad9-Hus1-Rad1 checkpoint clamp regulates interaction of TopBP1 with ATR.
2007,
Pubmed
,
Xenbase
Lee,
The Mre11-Rad50-Nbs1 (MRN) complex has a specific role in the activation of Chk1 in response to stalled replication forks.
2013,
Pubmed
,
Xenbase
Lieberman,
Rad9, an evolutionarily conserved gene with multiple functions for preserving genomic integrity.
2006,
Pubmed
Liu,
Regulation of TopBP1 oligomerization by Akt/PKB for cell survival.
2006,
Pubmed
Liu,
Regulation of E2F1 by BRCT domain-containing protein TopBP1.
2003,
Pubmed
Liu,
Regulation of p53 by TopBP1: a potential mechanism for p53 inactivation in cancer.
2009,
Pubmed
Lu,
Chromatin-bound NLS proteins recruit membrane vesicles and nucleoporins for nuclear envelope assembly via importin-α/β.
2012,
Pubmed
,
Xenbase
MacDougall,
The structural determinants of checkpoint activation.
2007,
Pubmed
,
Xenbase
Matsuoka,
ATM and ATR substrate analysis reveals extensive protein networks responsive to DNA damage.
2007,
Pubmed
Mordes,
TopBP1 activates ATR through ATRIP and a PIKK regulatory domain.
2008,
Pubmed
Mosammaparast,
Karyopherins: from nuclear-transport mediators to nuclear-function regulators.
2004,
Pubmed
Moudry,
Nucleoporin NUP153 guards genome integrity by promoting nuclear import of 53BP1.
2012,
Pubmed
Oldenburg,
Genetic susceptibility for breast cancer: how many more genes to be found?
2007,
Pubmed
Radu,
Identification of a protein complex that is required for nuclear protein import and mediates docking of import substrate to distinct nucleoporins.
1995,
Pubmed
,
Xenbase
Rollenhagen,
Importin beta-depending nuclear import pathways: role of the adapter proteins in the docking and releasing steps.
2003,
Pubmed
,
Xenbase
Schüchner,
Nuclear targeting and cell cycle regulatory function of human BARD1.
2005,
Pubmed
Shiotani,
Single-stranded DNA orchestrates an ATM-to-ATR switch at DNA breaks.
2009,
Pubmed
Smith,
The ATM-Chk2 and ATR-Chk1 pathways in DNA damage signaling and cancer.
2010,
Pubmed
Soderholm,
Importazole, a small molecule inhibitor of the transport receptor importin-β.
2011,
Pubmed
,
Xenbase
Sokka,
Function of TopBP1 in genome stability.
2010,
Pubmed
Stiff,
ATR-dependent phosphorylation and activation of ATM in response to UV treatment or replication fork stalling.
2006,
Pubmed
Toledo,
Targeting ATR and Chk1 kinases for cancer treatment: a new model for new (and old) drugs.
2011,
Pubmed
Tseng,
Importin KPNA2 is required for proper nuclear localization and multiple functions of NBS1.
2005,
Pubmed
Van,
Continued primer synthesis at stalled replication forks contributes to checkpoint activation.
2010,
Pubmed
,
Xenbase
Van Hatten,
The Xenopus Xmus101 protein is required for the recruitment of Cdc45 to origins of DNA replication.
2002,
Pubmed
,
Xenbase
Willis,
Study of the DNA damage checkpoint using Xenopus egg extracts.
2012,
Pubmed
,
Xenbase
Willis,
APE2 is required for ATR-Chk1 checkpoint activation in response to oxidative stress.
2013,
Pubmed
,
Xenbase
Xu,
PML colocalizes with and stabilizes the DNA damage response protein TopBP1.
2003,
Pubmed
Yamane,
A DNA damage-regulated BRCT-containing protein, TopBP1, is required for cell survival.
2002,
Pubmed
Yamane,
A DNA-topoisomerase-II-binding protein with eight repeating regions similar to DNA-repair enzymes and to a cell-cycle regulator.
1997,
Pubmed
Yan,
TopBP1 and DNA polymerase-alpha directly recruit the 9-1-1 complex to stalled DNA replication forks.
2009,
Pubmed
,
Xenbase
Yan,
TopBP1 and DNA polymerase alpha-mediated recruitment of the 9-1-1 complex to stalled replication forks: implications for a replication restart-based mechanism for ATR checkpoint activation.
2009,
Pubmed
Yan,
Direct requirement for Xmus101 in ATR-mediated phosphorylation of Claspin bound Chk1 during checkpoint signaling.
2006,
Pubmed
,
Xenbase
Yan,
WD40-repeat protein WDR18 collaborates with TopBP1 to facilitate DNA damage checkpoint signaling.
2013,
Pubmed
,
Xenbase
Yang,
MCPH1/BRIT1 cooperates with E2F1 in the activation of checkpoint, DNA repair and apoptosis.
2008,
Pubmed
Yoo,
Ataxia-telangiectasia mutated (ATM)-dependent activation of ATR occurs through phosphorylation of TopBP1 by ATM.
2007,
Pubmed
,
Xenbase
Yoshida,
Expression of MCM10 and TopBP1 is regulated by cell proliferation and UV irradiation via the E2F transcription factor.
2004,
Pubmed
You,
CtIP links DNA double-strand break sensing to resection.
2009,
Pubmed
,
Xenbase
Zannini,
Karyopherin-alpha2 protein interacts with Chk2 and contributes to its nuclear import.
2003,
Pubmed
Zou,
Sensing DNA damage through ATRIP recognition of RPA-ssDNA complexes.
2003,
Pubmed
