4cc9

Crystal structure of human SAMHD1 (amino acid residues 582-626) bound to Vpx isolated from sooty mangabey and human DCAF1 (amino acid residues 1058-1396)

spinqualitylabelsall models 4cc9, resolution 2.47Å Show:Asymmetric Unit Biological Assembly Drag the structure with the mouse to rotate   Export Animated Image   Print3D Structural highlights 4cc9 is a 3 chain structure with sequence from Homo sapiens and Simian immunodeficiency virus. Full crystallographic information is available from OCA. For a guided tour on the structure components use FirstGlance. Method: X-ray diffraction, Resolution 2.473Å Ligands: PG4, ZN Resources: FirstGlance, OCA, PDBe, RCSB, PDBsum, ProSAT Function DCAF1_HUMAN Acts both as a substrate recognition component of E3 ubiquitin-protein ligase complexes and as an atypical serine/threonine-protein kinase, playing key roles in various processes such as cell cycle, telomerase regulation and histone modification. Probable substrate-specific adapter of a DCX (DDB1-CUL4-X-box) E3 ubiquitin-protein ligase complex, named CUL4A-RBX1-DDB1-DCAF1/VPRBP complex, which mediates ubiquitination and proteasome-dependent degradation of proteins such as NF2. Involved in the turnover of methylated proteins: recognizes and binds methylated proteins via its chromo domain, leading to ubiquitination of target proteins by the RBX1-DDB1-DCAF1/VPRBP complex (PubMed:23063525). The CUL4A-RBX1-DDB1-DCAF1/VPRBP complex is also involved in B-cell development: DCAF1 is recruited by RAG1 to ubiquitinate proteins, leading to limit error-prone repair during V(D)J recombination. Also part of the EDVP complex, an E3 ligase complex that mediates ubiquitination of proteins such as TERT, leading to TERT degradation and telomerase inhibition (PubMed:23362280). Also acts as an atypical serine/threonine-protein kinase that specifically mediates phosphorylation of 'Thr-120' of histone H2A (H2AT120ph) in a nucleosomal context, thereby repressing transcription. H2AT120ph is present in the regulatory region of many tumor suppresor genes, down-regulates their transcription and is present at high level in a number of tumors (PubMed:24140421). Involved in JNK-mediated apoptosis during cell competition process via its interaction with LLGL1 and LLGL2 (PubMed:20644714). (Microbial infection) In case of infection by HIV-1 virus, it is recruited by HIV-1 Vpr in order to hijack the CUL4A-RBX1-DDB1-DCAF1/VPRBP function leading to arrest the cell cycle in G2 phase, and also to protect the viral protein from proteasomal degradation by another E3 ubiquitin ligase. The HIV-1 Vpr protein hijacks the CUL4A-RBX1-DDB1-DCAF1/VPRBP complex to promote ubiquitination and degradation of proteins such as TERT and ZIP/ZGPAT. (Microbial infection) In case of infection by HIV-2 virus, it is recruited by HIV-2 Vpx in order to hijack the CUL4A-RBX1-DDB1-DCAF1/VPRBP function leading to enhanced efficiency of macrophage infection and promotion of the replication of cognate primate lentiviruses in cells of monocyte/macrophage lineage. Publication Abstract from PubMed Lentiviruses contain accessory genes that have evolved to counteract the effects of host cellular defence proteins that inhibit productive infection. One such restriction factor, SAMHD1, inhibits human immunodeficiency virus (HIV)-1 infection of myeloid-lineage cells as well as resting CD4+ T cells by reducing the cellular deoxynucleoside 5'-triphosphate (dNTP) concentration to a level at which the viral reverse transcriptase cannot function. In other lentiviruses, including HIV-2 and related simian immunodeficiency viruses (SIVs), SAMHD1 restriction is overcome by the action of viral accessory protein x (Vpx) or the related viral protein r (Vpr) that target and recruit SAMHD1 for proteasomal degradation. The molecular mechanism by which these viral proteins are able to usurp the host cell's ubiquitination machinery to destroy the cell's protection against these viruses has not been defined. Here we present the crystal structure of a ternary complex of Vpx with the human E3 ligase substrate adaptor DCAF1 and the carboxy-terminal region of human SAMHD1. Vpx is made up of a three-helical bundle stabilized by a zinc finger motif, and wraps tightly around the disc-shaped DCAF1 molecule to present a new molecular surface. This adapted surface is then able to recruit SAMHD1 via its C terminus, making it a competent substrate for the E3 ligase to mark for proteasomal degradation. The structure reported here provides a molecular description of how a lentiviral accessory protein is able to subvert the cell's normal protein degradation pathway to inactivate the cellular viral defence system. Structural basis of lentiviral subversion of a cellular protein degradation pathway.,Schwefel D, Groom HC, Boucherit VC, Christodoulou E, Walker PA, Stoye JP, Bishop KN, Taylor IA Nature. 2013 Dec 15. doi: 10.1038/nature12815. PMID:24336198 From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. See Also Serine/threonine protein kinase 3D structures VprBP 3D structures

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