Structural basis of DNA bridging by barrier-to-autointegration factor.
Barrier-to-autointegration factor (BAF) is a host cell protein that plays a crucial role in retroviral integration. Preintegration complexes (PICs) stripped of BAF lose their normal integration activity, which can be restored by incubation with purified BAF. BAF bridges double-stranded DNA both intra- and intermolecularly in a non-sequence-specific manner, leading to the formation of a nucleoprotein network. BAF also binds to the nuclear protein lamina-associated polypeptide 2 (LAP2), and is localized with chromatin during interphase and mitosis. The crystal structure of homodimeric human BAF has been determined to 1.9 A resolution. The fold of the BAF monomer resembles that of the second domain of RuvA. This comparison revealed the presence of the helix-hairpin-helix (HhH) nonspecific DNA binding motif within BAF. A novel feature of BAF's HhH motif is the occupation of the metal binding site by the epsilon-amino group of Lys 6, providing an alternative means of sequestering positive charge. Mutational analysis corroborates the HhH motif's prominent role in DNA binding and argues against a previously proposed helix-turn-helix (HTH) binding site located in another region of the monomer. A model of BAF bridging DNA via the HhH motif is proposed.
Laboratory of Molecular Biology, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Bethesda, MD 20892, USA.
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Umland
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Wei
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Craigie
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Davies
D000595:Amino Acid Sequence; D001665:Binding Sites / Q000235:genetics; D003198:Computer Simulation; D018360:Crystallography, X-Ray; D004247:DNA / Q000737:chemistry*; D004252:DNA Mutational Analysis; D004268:DNA-Binding Proteins / Q000737:chemistry* / Q000235:genetics; D019281:Dimerization; D019077:Helix-Turn-Helix Motifs / Q000235:genetics; D006801:Humans; D008958:Models, Molecular; D008969:Molecular Sequence Data; D008979:Moloney murine leukemia virus / Q000737:chemistry / Q000235:genetics; D016297:Mutagenesis, Site-Directed; D019906:Nuclear Magnetic Resonance, Biomolecular; D009687:Nuclear Proteins; D017510:Protein Folding; D012645:Selenomethionine / Q000737:chemistry; D012996:Solutions; D016662:Virus Integration
C501959:BANF1 protein, human; D004268:DNA-Binding Proteins; D009687:Nuclear Proteins; D012996:Solutions; D004247:DNA; D012645:Selenomethionine