Interrelación entre el virus de la gripe y la cromantina celular estudio del remodelador de cromantina CHD6, modulador negativo de la infección viral

• Autores: Roberto Alfonso Dunn
• Directores de la Tesis: Amelia Nieto Martín (dir. tes.)
• Lectura: En la Universidad Autónoma de Madrid ( España ) en 2011
• Idioma: español
• Tribunal Calificador de la Tesis: José María Almendral del Río (presid.), José Alcamí Pertejo (secret.), Blanca García Barreno (voc.), José Carlos Reyes Rosa (voc.), Albert Jordan Valles (voc.)
• Materias:
  • Química
    • Bioquímica
• Enlaces
  • Tesis en acceso abierto en: digitool-uam.greendata.es
• Resumen

  • A significant body of evidence underlines the close relationship between influenza virus polymerase activity and the cellular transcription machinery as well as with nuclear chromatin. Nevertheless, once viral transcription is finished, RNA polymerase II is degraded and cellular transcription is disrupted, thus contributing to the observed cellular shut-off.

    In this thesis, a new interaction of the viral polymerase with a nuclear transcription related factor, the chromatin remodeler CHD6 protein, is described. CHD6 interacts individually with PA and PB2 influenza virus polymerase subunits as well as with the entire polymerase complex. High virus titers were also obtained in CHD6 silenced cells, which highlights the role of CHD6 as a negative modulator of influenza virus growth.

    Numerous nuclear processes are affected during influenza virus infection. Taking into consideration CHD6 binding to the viral polymerase, changes in CHD6 behavior during virus infection were assayed.

    We found that CHD6 intranuclear localization changes from a rather uniformly punctuated distribution to a granulated pattern within the infected cell. Moreover, at late time post-infection there is an increase in CHD6 and viral RNPs binding to trimethylated lysines of histone 3 tails that mark inactive chromatin (H3K9me3 and H3K27me3). A specific downregulation of H3K4me3 transcriptionally active mark could also be observed, which could be due to the profound cellular transcription obstruction initiated at intermediate times postinfection.

    Additionally, It was also observed that infection with laboratory-passaged influenza virus strains and natural human isolates specifically degrades CHD6 protein. In contrast to what happens with RNAP II during influenza virus infection, CHD6 degradation is also triggered by the attenuated A/PR8/8/34 (PR8) and by the cold-adapted A/AnnArbor/6/60 (AA) strains, which are used as donor for vaccine seeds. Specific inhibitors of the proteasome pathway do not impede the degradation and, moreover, the expression of viral polymerase from its cloned cDNAs is sufficient to induce this effect. CHD6 degradation was also observed in lungs of influenza virus infected mice.

    Relocalization of CHD6 to inactive chromatin and its specific degradation, as well as a decrease of H3K4me3, could constitute additional pathogenic events used by the influenza virus to induce host cell shutoff. The behavior of CHD6 during infection is also in accordance with its role as a negative modulator of the influenza virus infection.