title: Spatiotemporal regulation of Heterochromatin Protein 1-alpha oligomerization and dynamics in live cells.
abstract: Heterochromatin protein 1 (HP1) is a central factor in establishing and maintaining the heterochromatin state. As consequence of playing a structural role in heterochromatin, HP1 proteins can have both an activating as well as repressive function in gene expression. Here we probe how oligomerisation of the HP1-α isoform modulates interaction with chromatin, by spatially resolved fluorescence correlation spectroscopy (FCS). We find from fluctuation analysis of HP1-α dynamics that this isoform exists as a dimer around the periphery of heterochromatin foci and these foci locally rotate with characteristic turn rates that range from 5-100 ms. From inhibition of HP1-α homo-oligomerization we find the slow turn rates (20-100 ms) are dimer dependent. From treatment with drugs that disrupt or promote chromatin compaction, we find that HP1-α dimers spatially redistribute to favor fast (5-10 ms) or slow (20-100 ms) turn rates. Collectively our results demonstrate HP1-α oligomerization is critical to the maintenance of heterochromatin and the tunable dynamics of this HP1 isoform.
authors.affiliation: 1] Laboratory for Fluorescence Dynamics, Department of Biomedical Engineering, University of California, Irvine, USA [2] Centre for Vascular Research and Australian Centre for NanoMedicine, University of New South Wales, Sydney, Australia.
authors.forename: Elizabeth
authors.initials: E
authors.lastname: Hinde
authors.affiliation: 1] Laboratory for Fluorescence Dynamics, Department of Biomedical Engineering, University of California, Irvine, USA [2] Center for Nanotechnology Innovation @NEST, Istituto Italiano di Tecnologia, Piazza San Silvestro 12 - 56127 Pisa, Italy.
authors.forename: Francesco
authors.initials: F
authors.lastname: Cardarelli
authors.affiliation: Laboratory for Fluorescence Dynamics, Department of Biomedical Engineering, University of California, Irvine, USA.
authors.forename: Enrico
authors.initials: E
authors.lastname: Gratton
mesh_terms: D000818:Animals; D002843:Chromatin / Q000737:chemistry* / Q000187:drug effects / Q000378:metabolism; D000090266:Chromobox Protein Homolog 5; D002868:Chromosomal Proteins, Non-Histone / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D003609:Dactinomycin / Q000494:pharmacology; D005786:Gene Expression Regulation; D049452:Green Fluorescent Proteins / Q000235:genetics / Q000378:metabolism; D051379:Mice; D056004:Molecular Dynamics Simulation; D041681:NIH 3T3 Cells; D020033:Protein Isoforms / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D055503:Protein Multimerization / Q000187:drug effects; D011993:Recombinant Fusion Proteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D013050:Spectrometry, Fluorescence / Q000379:methods
chemical_list: D002843:Chromatin; D002868:Chromosomal Proteins, Non-Histone; D020033:Protein Isoforms; D011993:Recombinant Fusion Proteins; C485184:enhanced green fluorescent protein; D000090266:Chromobox Protein Homolog 5; D049452:Green Fluorescent Proteins; D003609:Dactinomycin