title: Interactions of Histone Acetyltransferase p300 with the Nuclear Proteins Histone and HMGB1, As Revealed by Single Molecule Atomic Force Spectroscopy.
abstract: One of the important properties of the transcriptional coactivator p300 is histone acetyltransferase (HAT) activity that enables p300 to influence chromatin action via histone modulation. p300 can exert its HAT action upon the other nuclear proteins too--one notable example being the transcription-factor-like protein HMGB1, which functions also as a cytokine, and whose accumulation in the cytoplasm, as a response to tissue damage, is triggered by its acetylation. Hitherto, no information on the structure and stability of the complexes between full-length p300 (p300FL) (300 kDa) and the histone/HMGB1 proteins are available, probably due to the presence of unstructured regions within p300FL that makes it difficult to be crystallized. Herein, we have adopted the high-resolution atomic force microscopy (AFM) approach, which allows molecularly resolved three-dimensional contour mapping of a protein molecule of any size and structure. From the off-rate and activation barrier values, obtained using single molecule dynamic force spectroscopy, the biochemical proposition of preferential binding of p300FL to histone H3, compared to the octameric histone, can be validated. Importantly, from the energy landscape of the dissociation events, a model for the p300-histone and the p300-HMGB1 dynamic complexes that HAT forms, can be proposed. The lower unbinding forces of the complexes observed in acetylating conditions, compared to those observed in non-acetylating conditions, indicate that upon acetylation, p300 tends to weakly associate, probably as an outcome of charge alterations on the histone/HMGB1 surface and/or acetylation-induced conformational changes. To our knowledge, for the first time, a single molecule level treatment of the interactions of HAT, where the full-length protein is considered, is being reported.
authors.affiliation: Department of Biological Chemistry, Indian Association for the Cultivation of Science , Jadavpur, Kolkata 700 032, India.
authors.forename: S
authors.initials: S
authors.lastname: Banerjee
authors.affiliation: Department of Biological Chemistry, Indian Association for the Cultivation of Science , Jadavpur, Kolkata 700 032, India.
authors.forename: T
authors.initials: T
authors.lastname: Rakshit
authors.affiliation: Department of Biological Chemistry, Indian Association for the Cultivation of Science , Jadavpur, Kolkata 700 032, India.
authors.forename: S
authors.initials: S
authors.lastname: Sett
authors.affiliation: Department of Biological Chemistry, Indian Association for the Cultivation of Science , Jadavpur, Kolkata 700 032, India.
authors.forename: R
authors.initials: R
authors.lastname: Mukhopadhyay
mesh_terms: D024243:HMGB1 Protein / Q000378:metabolism*; D051548:Histone Acetyltransferases / Q000378:metabolism*; D006657:Histones / Q000378:metabolism*; D018625:Microscopy, Atomic Force; D013057:Spectrum Analysis / Q000379:methods*
chemical_list: D024243:HMGB1 Protein; D006657:Histones; D051548:Histone Acetyltransferases