title: Damaged DNA induced UV-damaged DNA-binding protein (UV-DDB) dimerization and its roles in chromatinized DNA repair.
abstract: UV light-induced photoproducts are recognized and removed by the nucleotide-excision repair (NER) pathway. In humans, the UV-damaged DNA-binding protein (UV-DDB) is part of a ubiquitin E3 ligase complex (DDB1-CUL4A(DDB2)) that initiates NER by recognizing damaged chromatin with concomitant ubiquitination of core histones at the lesion. We report the X-ray crystal structure of the human UV-DDB in a complex with damaged DNA and show that the N-terminal domain of DDB2 makes critical contacts with two molecules of DNA, driving N-terminal-domain folding and promoting UV-DDB dimerization. The functional significance of the dimeric UV-DDB [(DDB1-DDB2)(2)], in a complex with damaged DNA, is validated by electron microscopy, atomic force microscopy, solution biophysical, and functional analyses. We propose that the binding of UV-damaged DNA results in conformational changes in the N-terminal domain of DDB2, inducing helical folding in the context of the bound DNA and inducing dimerization as a function of nucleotide binding. The temporal and spatial interplay between domain ordering and dimerization provides an elegant molecular rationale for the unprecedented binding affinities and selectivities exhibited by UV-DDB for UV-damaged DNA. Modeling the DDB1-CUL4A(DDB2) complex according to the dimeric UV-DDB-AP24 architecture results in a mechanistically consistent alignment of the E3 ligase bound to a nucleosome harboring damaged DNA. Our findings provide unique structural and conformational insights into the molecular architecture of the DDB1-CUL4A(DDB2) E3 ligase, with significant implications for the regulation and overall organization of the proteins responsible for initiation of NER in the context of chromatin and for the consequent maintenance of genomic integrity.
authors: Department of Structural Biology, University of Pittsburgh School of Medicine, Pittsburgh, PA 15260, USA. jiyeh@pitt.edu
authors: Joanne I
authors: JI
authors: Yeh
authors: Arthur S
authors: AS
authors: Levine
authors: Shoucheng
authors: S
authors: Du
authors: Unmesh
authors: U
authors: Chinte
authors: Harshad
authors: H
authors: Ghodke
authors: Hong
authors: H
authors: Wang
authors: Haibin
authors: H
authors: Shi
authors: Ching L
authors: CL
authors: Hsieh
authors: James F
authors: JF
authors: Conway
authors: Bennett
authors: B
authors: Van Houten
authors: Vesna
authors: V
authors: Rapić-Otrin
mesh_terms: D002843:Chromatin / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D018360:Crystallography, X-Ray; D044842:Cullin Proteins / Q000737:chemistry / Q000378:metabolism; D004247:DNA / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D004249:DNA Damage; D004260:DNA Repair; D004268:DNA-Binding Proteins / Q000737:chemistry* / Q000378:metabolism; D006801:Humans; D018625:Microscopy, Atomic Force; D008854:Microscopy, Electron; D008958:Models, Molecular; D046912:Multiprotein Complexes / Q000737:chemistry / Q000378:metabolism / Q000648:ultrastructure; D009690:Nucleic Acid Conformation; D011485:Protein Binding; D017510:Protein Folding; D055503:Protein Multimerization; D017433:Protein Structure, Secondary; D017434:Protein Structure, Tertiary
chemical_list: C114234:CUL4A protein, human; D002843:Chromatin; D044842:Cullin Proteins; C091435:DDB1 protein, human; C117669:DDB2 protein, human; D004268:DNA-Binding Proteins; D046912:Multiprotein Complexes; D004247:DNA