The PHD domain of Np95 (mUHRF1) is involved in large-scale reorganization of pericentromeric heterochromatin.
Heterochromatic chromosomal regions undergo large-scale reorganization and progressively aggregate, forming chromocenters. These are dynamic structures that rapidly adapt to various stimuli that influence gene expression patterns, cell cycle progression, and differentiation. Np95-ICBP90 (m- and h-UHRF1) is a histone-binding protein expressed only in proliferating cells. During pericentromeric heterochromatin (PH) replication, Np95 specifically relocalizes to chromocenters where it highly concentrates in the replication factories that correspond to less compacted DNA. Np95 recruits HDAC and DNMT1 to PH and depletion of Np95 impairs PH replication. Here we show that Np95 causes large-scale modifications of chromocenters independently from the H3:K9 and H4:K20 trimethylation pathways, from the expression levels of HP1, from DNA methylation and from the cell cycle. The PHD domain is essential to induce this effect. The PHD domain is also required in vitro to increase access of a restriction enzyme to DNA packaged into nucleosomal arrays. We propose that the PHD domain of Np95-ICBP90 contributes to the opening and/or stabilization of dense chromocenter structures to support the recruitment of modifying enzymes, like HDAC and DNMT1, required for the replication and formation of PH.
Papait
Roberto
R
Department of Structural and Functional Biology, University of Insubria, 21052 Busto Arsizio (VA), Italy.
Pistore
Christian
C
Grazini
Ursula
U
Babbio
Federica
F
Cogliati
Sara
S
Pecoraro
Daniela
D
Brino
Laurent
L
Morand
Anne-Laure
AL
Dechampesme
Anne-Marie
AM
Spada
Fabio
F
Leonhardt
Heinrich
H
McBlane
Fraser
F
Oudet
Pierre
P
Bonapace
Ian Marc
IM
D000107:Acetylation; D000818:Animals; D022762:CCAAT-Enhancer-Binding Proteins / Q000502:physiology*; D002453:Cell Cycle; D002503:Centromere / Q000648:ultrastructure*; D002843:Chromatin / Q000737:chemistry; D019175:DNA Methylation; D006570:Heterochromatin / Q000737:chemistry / Q000502:physiology*; D006657:Histones / Q000737:chemistry; D051379:Mice; D008954:Models, Biological; D041681:NIH 3T3 Cells; D009707:Nucleosomes / Q000378:metabolism; D017434:Protein Structure, Tertiary; D034622:RNA Interference; D044767:Ubiquitin-Protein Ligases
D022762:CCAAT-Enhancer-Binding Proteins; D002843:Chromatin; D006570:Heterochromatin; D006657:Histones; D009707:Nucleosomes; C406364:UHRF1 protein, human; D044767:Ubiquitin-Protein Ligases