DOCSLIB.ORG

Structure of an XRCC1 BRCT Domain: a New Protein-Protein

Total Page：16

File Type：pdf, Size：1020Kb

Download full-text PDF Read full-text
Structure of an XRCC1 BRCT Domain: a New Protein-Protein The EMBO Journal Vol.17 No.21 pp.6404–6411, 1998 Structure of an XRCC1 BRCT domain: a new protein–protein interaction module Xiaodong Zhang1, Solange More´ ra1,2, and cell cycle control (Koonin et al., 1996; Bork et al., Paul A.Bates3, Philip C.Whitehead4, 1997; Callebaut and Mornon, 1997). It was first identified Arnold I.Coffer4, Karl Hainbucher1,5, in the C-terminal region of the breast cancer suppressor Rachel A.Nash6, Michael J.E.Sternberg3, protein BRCA1 and was thus named BRCT domain Tomas Lindahl6 and Paul S.Freemont1,7 (Koonin et al., 1996). Two mammalian proteins which contain BRCT domains and have functions in DNA repair, 1Molecular Structure and Function, 3Biomolecular Modelling, and DNA ligase III and XRCC1 protein, bind each other 4Protein Isolation and Cloning Laboratories, Imperial Cancer Research strongly (Ljungquist et al., 1994; Caldecott et al., 1995) 6 Fund, 44 Lincoln’s Inn Fields, London WC2A 3PX and ICRF Clare to form a heterodimer through specific interactions Hall Laboratories, South Mimms, Herts EN6 3LD, UK between their C-terminal BRCT domains (Nash et al., 2Present address: Laboratoire d’Enzymologie et de Biochimie 1997). Thus, the C-terminal stretch of 96 amino acids of Structurales, UPR9063 CNRS-Universite´ Paris-Sud, Baˆt. 34, 1 Avenue de la Terrasse, 91198-Gif-sur-Yvette, France XRCC1 is necessary and sufficient to bind DNA ligase 5Present address: Institut fu¨r Physikalische Chemie, Universita¨t Graz, III efficiently. A second, more N-terminal BRCT domain Heinrichstraße 28, 8010 Graz, Austria in XRCC1 interacts with poly(ADP-ribose) polymerase 7Corresponding author (Masson et al., 1998). Similar results have been obtained e-mail: [email protected] for the C-terminal BRCT region of DNA ligase IV, which X.Zhang and S.More´ra contributed equally to this work forms a heterodimer with the XRCC4 protein and is involved in DNA double-strand break repair (Critchlow The BRCT domain (BRCA1 C-terminus), first identi- et al., 1997). These data identify BRCT domains as fied in the breast cancer suppressor protein BRCA1, is protein–protein interaction entities, which can either bind an evolutionarily conserved protein–protein interaction different BRCT domains specifically or interact with other region of ~95 amino acids found in a large number of unknown protein folds. proteins involved in DNA repair, recombination and XRCC1 (633 amino acids) has no known enzymatic cell cycle control. Here we describe the first three- activity (Thompson et al., 1990) but apparently functions dimensional structure and fold of a BRCT domain as a scaffolding protein in the mammalian base excision- determined by X-ray crystallography at 3.2 Å reso- repair pathway. Thus, XRCC1 promotes the efficiency of lution. The structure has been obtained from the the repair process and serves to bring together DNA C-terminal region of the human DNA repair protein polymerase β and DNA ligase III, since these two enzymes XRCC1, and comprises a four-stranded parallel β-sheet do not interact directly (Kubota et al., 1996; Cappelli surrounded by three α-helices, which form an auto- et al., 1997). As observed for several proteins involved nomously folded domain. The compact XRCC1 struc- in the correction of abasic sites in DNA, deletion of the ture explains the observed sequence homology between XRCC1 gene in mice results in an embryonic lethal different BRCT motifs and provides a framework for phenotype (Tebbs et al., 1996). This is consistent with an modelling other BRCT domains. Furthermore, the essential role in removal of endogenous DNA damage. established structure of an XRCC1 BRCT homodimer However, two Chinese hamster ovary cell lines with suggests potential protein–protein interaction sites for mutations in XRCC1 have been isolated; these cells show the complementary BRCT domain in DNA ligase III, reduced ability to join single-strand breaks in DNA, with since these two domains form a stable heterodimeric concomitant cellular hypersensitivity to ionizing radiation complex. Based on the XRCC1 BRCT structure, we and alkylating agents (Thompson et al., 1990; Cappelli have constructed a model for the C-terminal BRCT et al., 1997; Shen et al., 1998). domain of BRCA1, which frequently is mutated in The BRCT domain was first identified by a database familial breast and ovarian cancer. The model allows search, comparing regions of the BRCA1 protein with insights into the effects of such mutations on the fold other available protein sequences (Koonin et al., 1996). of the BRCT domain. The BRCA1 gene encodes a 220 kDa nuclear phospho- Keywords: BRCA1/BRCT/protein–protein interaction/ protein in which structural changes confer susceptibility X-ray crystallography/XRCC1 to familial breast and ovarian cancer (Miki et al., 1994). Thus, inherited mutations associated with loss of activity of BRCA1 result in a greatly increased risk of women Introduction developing breast cancer (Easton, 1997). The detailed molecular functions of BRCA1 are unknown, but recently The BRCT domain is defined by distinct hydrophobic BRCA1 has been implicated in transcriptional regulation clusters of amino acids and is believed to occur as an and DNA repair (reviewed in Bertwistle and Ashworth, autonomous folding unit of ~95 amino acids. This domain 1998). Specifically, the C-terminal region of BRCA1 is found in proteins involved in DNA repair, recombination containing two BRCT domains acts as a transcriptional 6404 © Oxford University Press Crystal structure of an XRCC1 BRCT domain Table I. Crystallographic statistics a Diffraction Resolution (Å) No. of unique Redundancy I/σ Completeness Rsym Mosaicity data sets reflections (%) (outer shell) (°) Sel-Met 30–3.2 7526 4.7 6.2 99.5 7.2 (28.6) 0.2 Sel-Met 1 Pt 30–3.5 5570 10.5 7.9 100 12.7 (30.2) 0.6 Phasing statistics b c Sites Rcullis Phasing powers SIR FOM FOM after DM (centric/acentric) (centric/acentric) (20–3.5 Å)d (20–3.2 Å)e 2 0.66/0.63 1.44/1.65 0.285 0.81 Refinement statistics f Resolution No. of reflections Atoms Rcryst (%) Rfree (%) r.m.s. bond r.m.s.bond 2σ cutoff (work/free) length (Å) angle (°) 15–3.2 Å 6209/712 808 21.7 26.5 0.012 1.684 a Rsym 5 ΣiΣi|Ii – ,I.|/Σ,I., where Ii and ,I. are the observed and average intensity. |F –|F 1F || b PH P H Rcullis 5 , where FPH and FP are the derivative and native protein structure factors. |FPH – FP | F c P Phasing powers 5 〈〉, where FH is the calculated heavy-atom structure factor. FPH –|FP1FH| dSIR FOM: single isomorphous replacement figure of merit. eFOM after DM: figure of merit after density modifications using real space 2-fold NCS averaging and histogram matching. f10% of the data at 3.2 Å were set aside for free R-factor calculation. activation region in reporter assay systems (Chapman C-terminal BRCT domain to predict the structural con- and Verma, 1996). BRCA1 co-purifies with the RNA sequences of cancer-predisposing mutations found within polymerase II holoenzyme complex (Scully et al., 1997a), the domain. and a direct interaction between the RNA helicase A component of the holoenzyme and BRCA1 has been Results and discussion detected (Anderson et al., 1998). Moreover, BRCA1 is phosphorylated in response to DNA damage and associates The structure of the XRCC1 C-terminal BRCT with hRAD51 (Scully et al., 1997b), the human homologue domain of the Escherichia coli RecA protein, which plays a key The tertiary structure of the C-terminal BRCT domain role in homologous recombination and post-replication from human XRCC1 (residues 538–633; 96 residues) was repair. Recent data indicate that BRCA1 co-immuno- solved by X-ray crystallography to 3.2 Å resolution (see precipitates with p53, and can regulate p53-mediated gene Table I and Materials and methods for details), using expression with an absolute requirement for the most phases obtained from single isomorphous replacement, C-terminal BRCT domain, suggesting that BRCA1 func- further improved through density averaging, and refined tions as a coactivator of p53 (Ouchi et al., 1998). A to a free R-factor of 26.5% (Table I). The relatively large unique involvement of the second of two C-terminal unit cell and highly hydrated nature of the crystals obtained BRCT domains in heterodimer formation and tight binding were limiting factors in the resolution of the data. However, of its protein partner has also been observed for DNA ligase the final electron density map improved by 2-fold non- IV (Herrmann et al., 1998). Many different mutations in crystallographic-symmetry averaging and solvent flat- BRCA1 have been described [see the Breast Cancer tening showed clear density for main chain and most side Information Core (BIC) databases on the World Wide chains. This allowed an unambiguous trace of a model Web: http://www.nhgri.nih.gov/Intramural_research/Lab_ containing residues 538–633. The structure forms a com- transfer/Bic], the positions of which have been correlated pact globular α/β domain (~36 Å326 Å323 Å) consisting with a predisposition to breast and/or ovarian cancer of a four-stranded parallel β-sheet (with strand order (Gayther et al., 1995). β2β1β3β4) surrounded by three α-helices (α1-α3; Figure Here we report the first three-dimensional structure and 1A). The overall topology is β1α1β2β3α2β4α3, with two fold of a BRCT domain. This provides a structural basis α-helices (α1 and α3) on one side of the β-sheet and the to explain the observed sequence conservation of the third helix (α2) on the other (Figure 1A). The β-sheet BRCT family as well as giving insights into the function forms the core of the structure, with helix α1 forming of the XRCC1 BRCT domain in terms of specific protein– hydrophobic interactions with residues from β1 and β2.
Load more

Recommended publications
  • Kinetic Analysis of Human DNA Ligase III by Justin R. Mcnally A
    Kinetic Analysis of Human DNA Ligase III by Justin R. McNally A dissertation submitted in partial fulfillment of the requirements for the degree of Doctor of Philosophy (Biological Chemistry) in the University of Michigan 2019 Doctoral Committee: Associate Professor Patrick J. O’Brien, Chair Associate Professor Bruce A. Palfey Associate Professor JoAnn M. Sekiguchi Associate Professor Raymond C. Trievel Professor Thomas E. Wilson Justin R. McNally [email protected] ORCID iD: 0000-0003-2694-2410 © Justin R. McNally 2019 Table of Contents List of Tables iii List of Figures iv Abstract vii Chapter 1 Introduction to the human DNA ligases 1 Chapter 2 Kinetic Analyses of Single-Strand Break Repair by Human DNA Ligase III Isoforms Reveal Biochemical Differences from DNA Ligase I 20 Chapter 3 The LIG3 N-terminus, in its entirety, contributes to single-strand DNA break ligation 56 Chapter 4 Comparative end-joining by human DNA ligases I and III 82 Chapter 5 A real-time DNA ligase assay suitable for high throughput screening 113 Chapter 6 Conclusions and Future Directions 137 ii List of Tables Table 2.1: Comparison of kinetic parameters for multiple turnover ligation by human DNA ligases 31 Table 2.2: Comparison of single-turnover parameters of LIG3β and LIG1 34 Table 3.1: Comparison of LIG3β N-terminal mutant kinetic parameters 67 Table 4.1: Rate constants for sequential ligation by LIG3β 95 Table 5.1: Comparison of multiple turnover kinetic parameters determined by real-time fluorescence assay and reported values 129 iii List of Figures Figure
    [Show full text]
  • Structural Basis of Homologous Recombination
    Cellular and Molecular Life Sciences (2020) 77:3–18 https://doi.org/10.1007/s00018-019-03365-1 Cellular andMolecular Life Sciences REVIEW Structural basis of homologous recombination Yueru Sun1 · Thomas J. McCorvie1 · Luke A. Yates1 · Xiaodong Zhang1 Received: 10 October 2019 / Revised: 10 October 2019 / Accepted: 31 October 2019 / Published online: 20 November 2019 © The Author(s) 2019 Abstract Homologous recombination (HR) is a pathway to faithfully repair DNA double-strand breaks (DSBs). At the core of this pathway is a DNA recombinase, which, as a nucleoprotein flament on ssDNA, pairs with homologous DNA as a template to repair the damaged site. In eukaryotes Rad51 is the recombinase capable of carrying out essential steps including strand invasion, homology search on the sister chromatid and strand exchange. Importantly, a tightly regulated process involving many protein factors has evolved to ensure proper localisation of this DNA repair machinery and its correct timing within the cell cycle. Dysregulation of any of the proteins involved can result in unchecked DNA damage, leading to uncontrolled cell division and cancer. Indeed, many are tumour suppressors and are key targets in the development of new cancer therapies. Over the past 40 years, our structural and mechanistic understanding of homologous recombination has steadily increased with notable recent advancements due to the advances in single particle cryo electron microscopy. These have resulted in higher resolution structural models of the signalling proteins ATM (ataxia telangiectasia mutated), and ATR (ataxia telangi- ectasia and Rad3-related protein), along with various structures of Rad51. However, structural information of the other major players involved, such as BRCA1 (breast cancer type 1 susceptibility protein) and BRCA2 (breast cancer type 2 susceptibility protein), has been limited to crystal structures of isolated domains and low-resolution electron microscopy reconstructions of the full-length proteins.
    [Show full text]
  • Identification of Novel Interaction Partners of Ets-1: Focus on DNA Repair
    Article Identification of Novel Interaction Partners of Ets-1: Focus on DNA Repair Guillaume Brysbaert *, Jérôme de Ruyck, Marc Aumercier and Marc F. Lensink * University of Lille, CNRS UMR8576 UGSF, Institute for Structural and Functional Glycobiology, F-59000 Lille, France; [email protected] (J.R.); [email protected] (M.A.) * Correspondence: [email protected] (G.B.); [email protected] (M.F.L.); Tel.: +33-(0)3-2043-4883 Received: 31 January 2019; Accepted: 5 March 2019; Published: 8 March 2019 Abstract: The transcription factor Ets-1 (ETS proto-oncogene 1) shows low expression levels except in specific biological processes like haematopoiesis or angiogenesis. Elevated levels of expression are observed in tumor progression, resulting in Ets-1 being named an oncoprotein. It has recently been shown that Ets-1 interacts with two DNA repair enzymes, PARP-1 (poly(ADP-ribose) polymerase 1) and DNA-PK (DNA-dependent protein kinase), through two different domains and that these interactions play a role in cancer. Considering that Ets-1 can bind to distinctly different domains of two DNA repair enzymes, we hypothesized that the interaction can be transposed onto homologs of the respective domains. We have searched for sequence and structure homologs of the interacting ETS(Ets-1), BRCT(PARP-1) and SAP(DNA-PK) domains, and have identified several candidate binding pairs that are currently not annotated as such. Many of the Ets-1 partners are associated to DNA repair mechanisms. We have applied protein-protein docking to establish putative interaction poses and investigated these using centrality analyses at the protein residue level.
    [Show full text]
  • MDC1: the Art of Keeping Things in Focus
    View metadata, citation and similar papers at core.ac.uk brought to you by CORE provided by RERO DOC Digital Library Chromosoma (2010) 119:337–349 DOI 10.1007/s00412-010-0266-9 REVIEW MDC1: The art of keeping things in focus Stephanie Jungmichel & Manuel Stucki Received: 6 January 2010 /Revised: 5 February 2010 /Accepted: 14 February 2010 /Published online: 12 March 2010 # Springer-Verlag 2010 Abstract The chromatin structure is important for recog- system. Since DSBs are highly toxic lesions that can lead to nition and repair of DNA damage. Many DNA damage genomic rearrangements if they are not efficiently and response proteins accumulate in large chromatin domains accurately repaired, it is not surprising that cells have flanking sites of DNA double-strand breaks. The assembly evolved highly sophisticated mechanisms to counteract of these structures—usually termed DNA damage foci—is those threats. Based on a seminal Nature review article by primarily regulated by MDC1, a large nuclear mediator/ Zhou and Elledge in 2000, these mechanisms are often adaptor protein that is composed of several distinct referred to as the DNA damage response (DDR; Zhou and structural and functional domains. Here, we are summariz- Elledge 2000). ing the latest discoveries about the mechanisms by which The DDR is a conglomerate of signaling transduction MDC1 mediates DNA damage foci formation, and we are pathways consisting of sensors, transducers, and effectors. reviewing the considerable efforts taken to understand the Although it is often delineated as a linear pathway, it is functional implication of these structures. more accurately described as a network of interacting pathways that together execute the cellular response.
    [Show full text]
  • BRCT Domains: a Little More Than Kin, and Less Than Kind ⇑ Dietlind L
    View metadata, citation and similar papers at core.ac.uk brought to you by CORE provided by Elsevier - Publisher Connector FEBS Letters 586 (2012) 2711–2716 journal homepage: www.FEBSLetters.org Review BRCT domains: A little more than kin, and less than kind ⇑ Dietlind L. Gerloff a,1, Nicholas T. Woods b,1, April A. Farago a, Alvaro N.A. Monteiro b, a Department of Biomolecular Engineering, University of California, Santa Cruz, CA 95064, USA b Cancer Epidemiology Program, H. Lee Moffitt Cancer Center and Research Institute, Tampa, FL 33612, USA article info abstract Article history: BRCT domains are versatile protein modular domains found as single units or as multiple copies in Received 21 April 2012 more than 20 different proteins in the human genome. Interestingly, most BRCT-containing Accepted 1 May 2012 proteins function in the same biological process, the DNA damage response network, but show spec- Available online 11 May 2012 ificity in their molecular interactions. BRCT domains have been found to bind a wide array of ligands from proteins, phosphorylated linear motifs, and DNA. Here we discuss the biology of BRCT domains Edited by Marius Sudol, Gianni Cesareni, and how a domain-centric analysis can aid in the understanding of signal transduction events in the Giulio Superti-Furga and Wilhelm Just DNA damage response network. Ó 2012 Federation of European Biochemical Societies. Published by Elsevier B.V. All rights reserved. Keywords: BRCT domain Protein domain Phosphopeptide binding DNA damage response 1. The modular nature of the DNA damage response target sequences for the DDR kinases and phosphatases reveals a preponderance of phosphorylation events on serine and threonine When damage to DNA is detected a number of signaling events residues rather than phosphorylation on tyrosine residues as is are initiated at the site of damage in the chromatin and radiate to commonly found in several canonical growth factor receptor sig- other subcellular compartments.
    [Show full text]
  • Focus on DNA Repair Guillaume Brysbaert, Jerome De Ruyck, Marc Aumercier, Marc Lensink
    Identification of Novel Interaction Partners of Ets-1: Focus on DNA Repair Guillaume Brysbaert, Jerome de Ruyck, Marc Aumercier, Marc Lensink To cite this version: Guillaume Brysbaert, Jerome de Ruyck, Marc Aumercier, Marc Lensink. Identification of Novel Interaction Partners of Ets-1: Focus on DNA Repair. Genes, MDPI, 2019, 10 (3), pp.206. 10.3390/genes10030206. hal-02327233 HAL Id: hal-02327233 https://hal.archives-ouvertes.fr/hal-02327233 Submitted on 22 Oct 2019 HAL is a multi-disciplinary open access L’archive ouverte pluridisciplinaire HAL, est archive for the deposit and dissemination of sci- destinée au dépôt et à la diffusion de documents entific research documents, whether they are pub- scientifiques de niveau recherche, publiés ou non, lished or not. The documents may come from émanant des établissements d’enseignement et de teaching and research institutions in France or recherche français ou étrangers, des laboratoires abroad, or from public or private research centers. publics ou privés. G C A T T A C G G C A T genes Article Identification of Novel Interaction Partners of Ets-1: Focus on DNA Repair Guillaume Brysbaert * ,Jérôme de Ruyck, Marc Aumercier and Marc F. Lensink * University of Lille, CNRS UMR8576 UGSF, Institute for Structural and Functional Glycobiology, F-59000 Lille, France; [email protected] (J.d.R.); [email protected] (M.A.) * Correspondence: [email protected] (G.B.); [email protected] (M.F.L.); Tel.: +33-(0)3-2043-4883 Received: 31 January 2019; Accepted: 5 March 2019; Published: 8 March 2019 Abstract: The transcription factor Ets-1 (ETS proto-oncogene 1) shows low expression levels except in specific biological processes like haematopoiesis or angiogenesis.
    [Show full text]
  • Structural and Functional Atlas of Frameshift Variation Capacity in Human Genome
    Structural and functional atlas of frameshift variation capacity in human genome by Nan Hu A Thesis Submitted to the Faculty of the WORCESTER POLYTECHNIC INSTITUTE in partial fulfillment of the requirements for the Degree of Master of Science in Bioinformatics and computational biology May 2018 APPROVED: Professor Dmitry Korkin, Thesis Advisor Professor Elizabeth F. Ryder, Thesis Reader Professor Dmitry Korkin, Head of Department Structural and functional atlas of frameshift variation capacity in human genome Abstract Currently, it is widely accepted that frameshift mutations yield truncated and dysfunctional proteins. Frameshift mutation products are mainly non-functional, abnormal, polypeptides and therefore have gained little attention from the point of view of their structural and functional analyses. However, recent studies have shown that frameshift proteins do have structures and can be functional. While most studies about frameshift mutation focus on the nucleotide sequence level, here we simulate and directly analyze frameshift mutation on the protein domain level. We focus on the protein domain, because it is the smallest structural and functional protein unit. By using protein blast tool to analyze the protein domain yield from all coding gene sequences in the human genome (45,139 mRNAs), we found out that 11,313 polypeptide sequences resulting from +1 frameshift mutation and 10,278 sequences resulting from +2 frameshift mutation are homologous to the existing proteins and could potentially carry out a function. Moreover, for 464 and 448 frameshift products in each type, respectively, we detected at least one protein domain by using Interproscan tool. We also compared the genes where we found the frameshift-produced protein domains with the genes associated with frameshift mutations reported by Clinvar database.
    [Show full text]
  • From BRCA1 to RAP1: a Widespread BRCT Module Closely Associated
    FEBS 17918 FEBS Letters 400 (1997) 25-30 From BRCAl to RAPl: a widespread BRCT module closely associated with DNA repair Isabelle Callebaut*, Jean-Paul Mornon Systemes Moleculaires & Biologie Structurale, Laboratoire de Mineralogie-Cristallographie, CNRS URA09, Universites Paris 6 and Paris 7, case 115, T.16, 4 place Jussieu, 75252 Paris Cedex 05, France Received 26 September 1996 pears to be tumor-type specific as BRCAl cannot inhibit the Abstract Inherited mutations in BRCAl predispose to breast and ovarian cancer, but the biological function of the BRCAl growth of some other cancer cell lines, nor can it inhibit the protein has remained largely elusive. The recent correspondence growth of normal fibroblasts [8]. of Koonin et al. [Koonin, E.V., Altschul, S.F. and Bork, P. BRCAl encodes a predicted protein of 1863 amino acids (1996) Nature Genet. 13, 266-267] has emphasized the potential containing in its NH2-terminus a single CsHQ-type zinc fin- importance of the BRCAl C-terminal region for BRCAl- ger domain, also referred to as the RING finger or A-box and mediated breast cancer suppression, as this domain shows found in various proteins showing transactivation activity for similarities with the C-terminal regions of a p53-binding protein a number of viral and cellular genes [1,9]. The rest of the (53BP1), the yeast RAD9 protein involved in DNA repair, and protein was initially reported to contain no significant similar- two uncharacterized, hypothetical proteins (KIAA0170 and ities to any known genes. A recent report paradoxically sug- SPAC19G10.7). The highlighted domain has been suggested to gests that the BRCAl protein, whose sequence is found to be the result of an internal duplication, each of the tandem domains being designated as a 'BRCT domain' (for BRCAl C- match with a 'granin' consensus, might be secreted and so terminus).
    [Show full text]
  • The FHA and BRCT Domains Recognize ADP-Ribosylation During DNA Damage Response
    Downloaded from genesdev.cshlp.org on September 27, 2021 - Published by Cold Spring Harbor Laboratory Press The FHA and BRCT domains recognize ADP-ribosylation during DNA damage response Mo Li,1 Lin-Yu Lu,1 Chao-Yie Yang,2,3,4 Shaomeng Wang,2,3,4 and Xiaochun Yu1,5 1Division of Molecular Medicine and Genetics, Department of Internal Medicine, University of Michigan, Ann Arbor, Michigan 48109, USA; 2Department of Internal Medicine, 3Department of Pharmacology, 4Department of Medicinal Chemistry, University of Michigan, Ann Arbor, Michigan 48109, USA Poly-ADP-ribosylation is a unique post-translational modification participating in many biological processes, such as DNA damage response. Here, we demonstrate that a set of Forkhead-associated (FHA) and BRCA1 C-terminal (BRCT) domains recognizes poly(ADP-ribose) (PAR) both in vitro and in vivo. Among these FHA and BRCT domains, the FHA domains of APTX and PNKP interact with iso-ADP-ribose, the linkage of PAR, whereas the BRCT domains of Ligase4, XRCC1, and NBS1 recognize ADP-ribose, the basic unit of PAR. The interactions between PAR and the FHA or BRCT domains mediate the relocation of these domain-containing proteins to DNA damage sites and facilitate the DNA damage response. Moreover, the interaction between PAR and the NBS1 BRCT domain is important for the early activation of ATM during DNA damage response and ATM-dependent cell cycle checkpoint activation. Taken together, our results demonstrate two novel PAR-binding modules that play important roles in DNA damage response. [Keywords: poly(ADP-ribose); PAR binding domain; DNA damage] Supplemental material is available for this article.
    [Show full text]