4E5Z: Damaged Dna Induced Uv-Damaged Dna-Binding Protein (Uv-Ddb) Dimerization And Its Roles In Chromatinized Dna Repair

Citation:
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.
PDB ID: 4E5ZDownload
MMDB ID: 102169
PDB Deposition Date: 2012/3/15
Updated in MMDB: 2012/10
Experimental Method:
x-ray diffraction
Resolution: 3.22  Å
Source Organism:
synthetic construct
Similar Structures:
Biological Unit for 4E5Z: tetrameric; determined by author and by software (PISA)
Molecular Components in 4E5Z
Label Count Molecule
Proteins (2 molecules)
1
DNA Damage-binding Protein 1(Gene symbol: DDB1)
Molecule annotation
1
DNA Damage-binding Protein 2(Gene symbol: DDB2)
Molecule annotation
Nucleotides(2 molecules)
1
Ap24 DNA Strand
Molecule annotation
1
Ap24 DNA Complementary Strand
Molecule annotation
* Click molecule labels to explore molecular sequence information.

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