Perturbation of Chromatin Structure Globally Affects Localization and Recruitment of Splicing Factors

• Autores: Schor, I.E.; Llères, D.; Risso, G.J.; Pawellek, A.; Ule, J.; Lamond, A.I.; Kornblihtt, A.R.
• Año de publicación: 2012
• Idioma: inglés
• Tipo de recurso: artículo
• Fuente: PLoS ONE 2012;7(11)
• Materia: enhanced green fluorescent protein; heterochromatin protein 1; heterochromatin protein 1alpha; histone H3; histone H4; messenger RNA; nuclear protein; protein SRSF1; protein SRSF2; trichostatin A; unclassified drug; untranslated RNA; article; bioaccumulation; cell nucleus; cellular distribution; chromatin structure; controlled study; gene control; gene function; histone acetylation; human; human cell; MALAT1 gene; molecular imaging; molecular model; NCAM gene; Neat1 gene; protein determination; protein function; protein RNA binding; regulatory mechanism; RNA analysis; RNA gene; RNA splicing; spliceosome; structure analysis; Acetylation; Alternative Splicing; Animals; Cell Line; Cell Nucleus; Chromatin; Histones; Humans; Hydroxamic Acids; Membrane Potentials; Models, Biological; Protein Binding; Protein Transport; Ribonucleoproteins; RNA Precursors; RNA Splice Sites; RNA Splicing; RNA, Long Untranslated
• Institución: Universidad Nacional de Buenos Aires. Facultad de Ciencias Exactas y Naturales

Chromatin structure is an important factor in the functional coupling between transcription and mRNA processing, not only by regulating alternative splicing events, but also by contributing to exon recognition during constitutive splicing. We observed that depolarization of neuroblastoma cell membrane potential, which triggers general histone acetylation and regulates alternative splicing, causes a concentration of SR proteins in nuclear speckles. This prompted us to analyze the effect of chromatin structure on splicing factor distribution and dynamics. Here, we show that induction of histone hyper-acetylation results in the accumulation in speckles of multiple splicing factors in different cell types. In addition, a similar effect is observed after depletion of the heterochromatic protein HP1α, associated with repressive chromatin. We used advanced imaging approaches to analyze in detail both the structural organization of the speckle compartment and nuclear distribution of splicing factors, as well as studying direct interactions between splicing factors and their association with chromatin in vivo. The results support a model where perturbation of normal chromatin structure decreases the recruitment efficiency of splicing factors to nascent RNAs, thus causing their accumulation in speckles, which buffer the amount of free molecules in the nucleoplasm. To test this, we analyzed the recruitment of the general splicing factor U2AF65 to nascent RNAs by iCLIP technique, as a way to monitor early spliceosome assembly. We demonstrate that indeed histone hyper-acetylation decreases recruitment of U2AF65 to bulk 3′ splice sites, coincident with the change in its localization. In addition, prior to the maximum accumulation in speckles, ~20% of genes already show a tendency to decreased binding, while U2AF65 seems to increase its binding to the speckle-located ncRNA MALAT1. All together, the combined imaging and biochemical approaches support a model where chromatin structure is essential for efficient co-transcriptional recruitment of general and regulatory splicing factors to pre-mRNA. © 2012 Schor et al.
Fil:Schor, I.E. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales; Argentina.
Fil:Risso, G.J. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales; Argentina.
Fil:Kornblihtt, A.R. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales; Argentina.