title: Poly(ADP-ribosylation) protects maternally derived histones from proteolysis after fertilization.
abstract: Fertilization in sea urchins is followed by the replacement of sperm-specific histones by cleavage-stage histone variants recruited from maternal stores. Such remodelling of zygote chromatin involves a cysteine proteinase that degrades the sperm-specific histones in a selective manner, leaving the maternal cleavage-stage histone variants intact. The mechanism that determines the selectivity of the sperm-histone-selective proteinase (SpH-proteinase) was analysed by focusing on the post-translational modification status of both sets of histones. It has previously been reported that only native cleavage-stage histones are poly(ADP-ribosylated), whereas the sperm-specific histones are not modified. To determine whether the poly(ADP-ribose) moiety afforded protection from degradation, the ADP-ribose polymers were removed from the cleavage-stage histones in vitro; these proteins were then assayed as potential substrates of the SpH-proteinase. Strikingly, the cleavage-stage histone variants were extensively degraded after the enzymic removal of their ADP-ribose moieties. In addition, the SpH cysteine proteinase was not inhibited by isolated poly(ADP-ribose) polymers. Consequently, only poly(ADP-ribosylated) cleavage-stage histone variants are protected from proteolysis. These results demonstrate a novel role for this type of post-translational modification, namely the protection of nuclear proteins against nuclear proteinases after fertilization.
authors.affiliation: Department of Molecular Biology, Universidad de Concepción, Casilla 160-C, Concepción, Chile.
authors.forename: V
authors.initials: V
authors.lastname: Morin
authors.forename: F
authors.initials: F
authors.lastname: Diaz
authors.forename: M
authors.initials: M
authors.lastname: Montecino
authors.forename: L
authors.initials: L
authors.lastname: Fothergill-Gilmore
authors.forename: M
authors.initials: M
authors.lastname: Puchi
authors.forename: M
authors.initials: M
authors.lastname: Imschenetzky
mesh_terms: D000818:Animals; D001704:Biopolymers; D005260:Female; D005306:Fertilization; D006657:Histones / Q000378:metabolism*; D011064:Poly Adenosine Diphosphate Ribose / Q000378:metabolism*; D012617:Sea Urchins
chemical_list: D001704:Biopolymers; D006657:Histones; D011064:Poly Adenosine Diphosphate Ribose