title: Evidence supporting a critical contribution of intrinsically disordered regions to the biochemical behavior of full-length human HP1γ.
abstract: HP1γ, a non-histone chromatin protein, has elicited significant attention because of its role in gene silencing, elongation, splicing, DNA repair, cell growth, differentiation, and many other cancer-associated processes, including therapy resistance. These characteristics make it an ideal target for developing small drugs for both mechanistic experimentation and potential therapies. While high-resolution structures of the two globular regions of HP1γ, the chromo- and chromoshadow domains, have been solved, little is currently known about the conformational behavior of the full-length protein. Consequently, in the current study, we use threading, homology-based molecular modeling, molecular mechanics calculations, and molecular dynamics simulations to develop models that allow us to infer properties of full-length HP1γ at an atomic resolution level. HP1γ appears as an elongated molecule in which three Intrinsically Disordered Regions (IDRs, 1, 2, and 3) endow this protein with dynamic flexibility, intermolecular recognition properties, and the ability to integrate signals from various intracellular pathways. Our modeling also suggests that the dynamic flexibility imparted to HP1γ by the three IDRs is important for linking nucleosomes with PXVXL motif-containing proteins, in a chromatin environment. The importance of the IDRs in intermolecular recognition is illustrated by the building and study of both IDR2 HP1γ-importin-α and IDR1 and IDR2 HP1γ-DNA complexes. The ability of the three IDRs for integrating cell signals is demonstrated by combined linear motif analyses and molecular dynamics simulations showing that posttranslational modifications can generate a histone mimetic sequence within the IDR2 of HP1γ, which when bound by the chromodomain can lead to an autoinhibited state. Combined, these data underscore the importance of IDRs 1, 2, and 3 in defining the structural and dynamic properties of HP1γ, discoveries that have both mechanistic and potentially biomedical relevance.
authors.affiliation: Laboratory of Epigenetics and Chromatin Dynamics, Gastroenterology Research Unit, Department of Biochemistry and Molecular Biology, Mayo Clinic, 200 First Street SW, Guggenheim 10, Rochester, MN, 55905, USA.|Laboratory of Epigenetics and Chromatin Dynamics, Gastroenterology Research Unit, Department of Biophysics, Mayo Clinic, Rochester, MN, USA.|Laboratory of Epigenetics and Chromatin Dynamics, Gastroenterology Research Unit, Department of Medicine, Mayo Clinic, Rochester, MN, USA.|Medical Scientist Training Program, University of Iowa, Iowa City, IA, USA.
authors.forename: Gabriel
authors.initials: G
authors.lastname: Velez
authors.affiliation: Laboratory of Epigenetics and Chromatin Dynamics, Gastroenterology Research Unit, Department of Biochemistry and Molecular Biology, Mayo Clinic, 200 First Street SW, Guggenheim 10, Rochester, MN, 55905, USA.|Laboratory of Epigenetics and Chromatin Dynamics, Gastroenterology Research Unit, Department of Biophysics, Mayo Clinic, Rochester, MN, USA.|Laboratory of Epigenetics and Chromatin Dynamics, Gastroenterology Research Unit, Department of Medicine, Mayo Clinic, Rochester, MN, USA.
authors.forename: Marisa
authors.initials: M
authors.lastname: Lin
authors.affiliation: Laboratory of Epigenetics and Chromatin Dynamics, Gastroenterology Research Unit, Department of Biochemistry and Molecular Biology, Mayo Clinic, 200 First Street SW, Guggenheim 10, Rochester, MN, 55905, USA.|Laboratory of Epigenetics and Chromatin Dynamics, Gastroenterology Research Unit, Department of Biophysics, Mayo Clinic, Rochester, MN, USA.|Laboratory of Epigenetics and Chromatin Dynamics, Gastroenterology Research Unit, Department of Medicine, Mayo Clinic, Rochester, MN, USA.
authors.forename: Trace
authors.initials: T
authors.lastname: Christensen
authors.affiliation: Laboratory of Epigenetics and Chromatin Dynamics, Gastroenterology Research Unit, Department of Biochemistry and Molecular Biology, Mayo Clinic, 200 First Street SW, Guggenheim 10, Rochester, MN, 55905, USA.|Laboratory of Epigenetics and Chromatin Dynamics, Gastroenterology Research Unit, Department of Biophysics, Mayo Clinic, Rochester, MN, USA.|Laboratory of Epigenetics and Chromatin Dynamics, Gastroenterology Research Unit, Department of Medicine, Mayo Clinic, Rochester, MN, USA.
authors.forename: William A
authors.initials: WA
authors.lastname: Faubion
authors.affiliation: Laboratory of Epigenetics and Chromatin Dynamics, Gastroenterology Research Unit, Department of Biochemistry and Molecular Biology, Mayo Clinic, 200 First Street SW, Guggenheim 10, Rochester, MN, 55905, USA. lomberk.gwen@mayo.edu.|Laboratory of Epigenetics and Chromatin Dynamics, Gastroenterology Research Unit, Department of Biophysics, Mayo Clinic, Rochester, MN, USA. lomberk.gwen@mayo.edu.|Laboratory of Epigenetics and Chromatin Dynamics, Gastroenterology Research Unit, Department of Medicine, Mayo Clinic, Rochester, MN, USA. lomberk.gwen@mayo.edu.
authors.forename: Gwen
authors.initials: G
authors.lastname: Lomberk
authors.affiliation: Laboratory of Epigenetics and Chromatin Dynamics, Gastroenterology Research Unit, Department of Biochemistry and Molecular Biology, Mayo Clinic, 200 First Street SW, Guggenheim 10, Rochester, MN, 55905, USA. urrutia.raul@mayo.edu.|Laboratory of Epigenetics and Chromatin Dynamics, Gastroenterology Research Unit, Department of Biophysics, Mayo Clinic, Rochester, MN, USA. urrutia.raul@mayo.edu.|Laboratory of Epigenetics and Chromatin Dynamics, Gastroenterology Research Unit, Department of Medicine, Mayo Clinic, Rochester, MN, USA. urrutia.raul@mayo.edu.
authors.forename: Raul
authors.identifier: http://orcid.org/0000-0002-1640-6780
authors.initials: R
authors.lastname: Urrutia
mesh_terms: D020816:Amino Acid Motifs; D002868:Chromosomal Proteins, Non-Histone / Q000737:chemistry* / Q000235:genetics; D006801:Humans; D056004:Molecular Dynamics Simulation; D017434:Protein Structure, Tertiary
chemical_list: C518294:CBX3 protein, human; D002868:Chromosomal Proteins, Non-Histone
keywords: CBX3; Chromatin; Epigenetics; HP1; HP1γ; Molecular dynamics; Molecular modeling