RESUMO
Regulation of the E2F family of transcription factors is important in control of cellular proliferation; dysregulation of the E2Fs is a hallmark of many cancers. One member of the E2F family, E2F1, also has the paradoxical ability to induce apoptosis; however, the mechanisms underlying this selectivity are not fully understood. We now identify a nucleolar protein, RRP1B, as an E2F1-specific transcriptional target. We characterize the RRP1B promoter and demonstrate its selective response to E2F1. Consistent with the activation of E2F1 activity upon DNA damage, RRP1B is induced by several DNA-damaging agents. Importantly, RRP1B is required for the expression of certain E2F1 proapoptotic target genes and the induction of apoptosis by DNA-damaging agents. This activity is mediated in part by complex formation between RRP1B and E2F1 on selective E2F1 target gene promoters. Interaction between RRP1B and E2F1 can be found inside the nucleolus and diffuse nucleoplasmic punctates. Thus, E2F1 makes use of its transcriptional target RRP1B to activate other genes directly involved in apoptosis. Our data also suggest an underappreciated role for nucleolar proteins in transcriptional regulation.
Assuntos
Apoptose , Proteínas Cromossômicas não Histona/fisiologia , Fator de Transcrição E2F1/fisiologia , Animais , Células Cultivadas , Proteínas Cromossômicas não Histona/genética , Proteínas Cromossômicas não Histona/metabolismo , Dano ao DNA , Fator de Transcrição E2F1/genética , Fator de Transcrição E2F1/metabolismo , Humanos , Camundongos , Proteínas Nucleares/genética , Proteínas Nucleares/metabolismo , Proteínas Nucleares/fisiologia , Regiões Promotoras Genéticas , Ligação Proteica , Transcrição Gênica , Ativação TranscricionalRESUMO
We have reprogrammed the stimulus-responsive conformational change property of a virus nanoparticle (VNP) to enable the surface exposure of metal binding motifs upon activation with heat. The VNP is based on the widely investigated adeno-associated virus (AAV). An intrinsic bioactive functionality of AAV was genetically replaced with a hexahistidine (His) tag. The peptide domain with the inserted His tag is normally inaccessible. Upon external stimulation with heat, the VNP undergoes a conformational change, resulting in externalization of His tag-containing domains and the conferred ability to bind metal. We show that beyond this newfound functionality of the capsid, the VNPs maintain many of the wild-type capsid properties. Our work lays the groundwork for developing stimulus-responsive VNPs that can be used as "smart" building blocks for the creation of higher order structures.