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==Fragment-based screening identifies a new area for inhibitor binding to checkpoint kinase 2 (CHK2)==
<StructureSection load='4bdj' size='340' side='right'caption='[[4bdj]], [[Resolution|resolution]] 3.01&Aring;' scene=''>
== Structural highlights ==
<table><tr><td colspan='2'>[[4bdj]] is a 1 chain structure with sequence from [https://en.wikipedia.org/wiki/Homo_sapiens Homo sapiens]. Full crystallographic information is available from [http://oca.weizmann.ac.il/oca-bin/ocashort?id=4BDJ OCA]. For a <b>guided tour on the structure components</b> use [https://proteopedia.org/fgij/fg.htm?mol=4BDJ FirstGlance]. <br>
</td></tr><tr id='method'><td class="sblockLbl"><b>[[Empirical_models|Method:]]</b></td><td class="sblockDat" id="methodDat">X-ray diffraction, [[Resolution|Resolution]] 3.01&#8491;</td></tr>
<tr id='ligand'><td class="sblockLbl"><b>[[Ligand|Ligands:]]</b></td><td class="sblockDat" id="ligandDat"><scene name='pdbligand=NO3:NITRATE+ION'>NO3</scene>, <scene name='pdbligand=Z2M:3-CYCLOPROPYL-4-(FURAN-2-YL)-1H-PYRAZOLO[3,4-B]PYRIDINE'>Z2M</scene></td></tr>
<tr id='resources'><td class="sblockLbl"><b>Resources:</b></td><td class="sblockDat"><span class='plainlinks'>[https://proteopedia.org/fgij/fg.htm?mol=4bdj FirstGlance], [http://oca.weizmann.ac.il/oca-bin/ocaids?id=4bdj OCA], [https://pdbe.org/4bdj PDBe], [https://www.rcsb.org/pdb/explore.do?structureId=4bdj RCSB], [https://www.ebi.ac.uk/pdbsum/4bdj PDBsum], [https://prosat.h-its.org/prosat/prosatexe?pdbcode=4bdj ProSAT]</span></td></tr>
</table>
== Disease ==
[https://www.uniprot.org/uniprot/CHK2_HUMAN CHK2_HUMAN] Defects in CHEK2 are associated with Li-Fraumeni syndrome 2 (LFS2) [MIM:[https://omim.org/entry/609265 609265]; a highly penetrant familial cancer phenotype usually associated with inherited mutations in p53/TP53.<ref>PMID:11719428</ref>   Defects in CHEK2 may be a cause of susceptibility to prostate cancer (PC) [MIM:[https://omim.org/entry/176807 176807]. It is a malignancy originating in tissues of the prostate. Most prostate cancers are adenocarcinomas that develop in the acini of the prostatic ducts. Other rare histopathologic types of prostate cancer that occur in approximately 5% of patients include small cell carcinoma, mucinous carcinoma, prostatic ductal carcinoma, transitional cell carcinoma, squamous cell carcinoma, basal cell carcinoma, adenoid cystic carcinoma (basaloid), signet-ring cell carcinoma and neuroendocrine carcinoma.  Defects in CHEK2 are found in some patients with osteogenic sarcoma (OSRC) [MIM:[https://omim.org/entry/259500 259500].  Defects in CHEK2 is a cause of susceptibility to breast cancer (BC) [MIM:[https://omim.org/entry/114480 114480]. A common malignancy originating from breast epithelial tissue. Breast neoplasms can be distinguished by their histologic pattern. Invasive ductal carcinoma is by far the most common type. Breast cancer is etiologically and genetically heterogeneous. Important genetic factors have been indicated by familial occurrence and bilateral involvement. Mutations at more than one locus can be involved in different families or even in the same case. Note=CHEK2 variants are associated with susceptibility to breast cancer and contribute to a substantial fraction of familial breast cancer (PubMed:12094328).<ref>PMID:12094328</ref> <ref>PMID:21618645</ref> 
== Function ==
[https://www.uniprot.org/uniprot/CHK2_HUMAN CHK2_HUMAN] Serine/threonine-protein kinase which is required for checkpoint-mediated cell cycle arrest, activation of DNA repair and apoptosis in response to the presence of DNA double-strand breaks. May also negatively regulate cell cycle progression during unperturbed cell cycles. Following activation, phosphorylates numerous effectors preferentially at the consensus sequence [L-X-R-X-X-S/T]. Regulates cell cycle checkpoint arrest through phosphorylation of CDC25A, CDC25B and CDC25C, inhibiting their activity. Inhibition of CDC25 phosphatase activity leads to increased inhibitory tyrosine phosphorylation of CDK-cyclin complexes and blocks cell cycle progression. May also phosphorylate NEK6 which is involved in G2/M cell cycle arrest. Regulates DNA repair through phosphorylation of BRCA2, enhancing the association of RAD51 with chromatin which promotes DNA repair by homologous recombination. Also stimulates the transcription of genes involved in DNA repair (including BRCA2) through the phosphorylation and activation of the transcription factor FOXM1. Regulates apoptosis through the phosphorylation of p53/TP53, MDM4 and PML. Phosphorylation of p53/TP53 at 'Ser-20' by CHEK2 may alleviate inhibition by MDM2, leading to accumulation of active p53/TP53. Phosphorylation of MDM4 may also reduce degradation of p53/TP53. Also controls the transcription of pro-apoptotic genes through phosphorylation of the transcription factor E2F1. Tumor suppressor, it may also have a DNA damage-independent function in mitotic spindle assembly by phosphorylating BRCA1. Its absence may be a cause of the chromosomal instability observed in some cancer cells.<ref>PMID:9836640</ref> <ref>PMID:9889122</ref> <ref>PMID:10097108</ref> <ref>PMID:10724175</ref> <ref>PMID:11298456</ref> <ref>PMID:12402044</ref> <ref>PMID:12810724</ref> <ref>PMID:12717439</ref> <ref>PMID:12607004</ref> <ref>PMID:16163388</ref> <ref>PMID:17380128</ref> <ref>PMID:17715138</ref> <ref>PMID:17101782</ref> <ref>PMID:18728393</ref> <ref>PMID:18644861</ref> <ref>PMID:18317453</ref> <ref>PMID:20364141</ref> 
<div style="background-color:#fffaf0;">
== Publication Abstract from PubMed ==
Checkpoint kinase 2 (CHK2) is an important serine/threonine kinase in the cellular response to DNA damage. A fragment-based screening campaign using a combination of a high-concentration AlphaScreen kinase assay and a biophysical thermal shift assay, followed by X-ray crystallography, identified a number of chemically different ligand-efficient CHK2 hinge-binding scaffolds that have not been exploited in known CHK2 inhibitors. In addition, it showed that the use of these orthogonal techniques allowed efficient discrimination between genuine hit matter and false positives from each individual assay technology. Furthermore, the CHK2 crystal structures with a quinoxaline-based fragment and its follow-up compound highlight a hydrophobic area above the hinge region not previously explored in rational CHK2 inhibitor design, but which might be exploited to enhance both potency and selectivity of CHK2 inhibitors.

Fragment-Based Screening Maps Inhibitor Interactions in the ATP-Binding Site of Checkpoint Kinase 2.,Silva-Santisteban MC, Westwood IM, Boxall K, Brown N, Peacock S, McAndrew C, Barrie E, Richards M, Mirza A, Oliver AW, Burke R, Hoelder S, Jones K, Aherne GW, Blagg J, Collins I, Garrett MD, van Montfort RL PLoS One. 2013 Jun 12;8(6):e65689. doi: 10.1371/journal.pone.0065689. Print 2013. PMID:23776527<ref>PMID:23776527</ref>

From MEDLINE&reg;/PubMed&reg;, a database of the U.S. National Library of Medicine.<br>
</div>
<div class="pdbe-citations 4bdj" style="background-color:#fffaf0;"></div>

==See Also==
*[[Serine/threonine protein kinase 3D structures|Serine/threonine protein kinase 3D structures]]
== References ==
<references/>
__TOC__
</StructureSection>
[[Category: Homo sapiens]]
[[Category: Large Structures]]
[[Category: Aherne GW]]
[[Category: Barrie E]]
[[Category: Blagg J]]
[[Category: Boxall K]]
[[Category: Brown N]]
[[Category: Burke R]]
[[Category: Collins I]]
[[Category: Garrett MD]]
[[Category: Hoelder S]]
[[Category: Jones K]]
[[Category: McAndrew C]]
[[Category: Mirza A]]
[[Category: Oliver AW]]
[[Category: Peacock S]]
[[Category: Richards M]]
[[Category: Silva-Santisteban MC]]
[[Category: Westwood IM]]
[[Category: Van Montfort RLM]]