RESUMO
Adenovirus type 2 (Ad2) imports its DNA genome through the nuclear pore complex (NPC) of cells in interphase for viral production. Here we identify the NPC-filament protein CAN/Nup214 as a docking site for incoming Ad2 capsids. Binding to CAN is independent of cytosolic factors. Capsids disassemble at NPCs to free their DNA for import. This process requires binding of nuclear histone H1 to the stably docked capsids and involves H1-import factors, restricting this irreversible process to the proximity of the nucleus. Our results provide a molecular mechanism for disassembly of Ad2 and reveal an unexpected function of histone H1 in virus-mediated DNA import.
Assuntos
Adenoviridae/genética , Proteínas do Capsídeo , DNA Viral/farmacocinética , Histonas/metabolismo , Complexo de Proteínas Formadoras de Poros Nucleares/metabolismo , Poro Nuclear/metabolismo , Transporte Ativo do Núcleo Celular/fisiologia , Sequência de Aminoácidos , Anticorpos/farmacologia , Capsídeo/genética , Capsídeo/imunologia , Capsídeo/metabolismo , Histonas/imunologia , Humanos , Neoplasias Pulmonares , Dados de Sequência Molecular , Complexo de Proteínas Formadoras de Poros Nucleares/imunologia , Ligação Proteica/fisiologia , Células Tumorais Cultivadas , alfa Carioferinas/metabolismo , beta Carioferinas/metabolismoRESUMO
We have designed and synthesized HIV-1 enhancer-binding polypeptides that were derived from bacteriophage 434 repressor. These peptides were 39-54 residues long and contained either the recognition helix or the entire helix-turn-helix motif of the DNA-binding domain of 434 repressor. The dissociation constant of the complex formed between the standard peptide (R42) and a synthetic 70-bp HIV enhancer DNA was ca. 10(-8) M. The specificity of the interaction of R42 with the two HIV enhancers was demonstrated by competitive band shift assays, stepwise displacement of the p50 subunit of transcription factor NF-kappa B from its two HIV enhancer binding sites, and DNase I footprinting; R42 seemed to protect best the two TTTCC sequences of the HIV enhancers against digestion by DNase I. R42 analogues with mutated recognition helix had lower DNA binding specificity. It remains to be investigated whether our artificial HIV enhancer-binding polypeptides are active in vivo.