Poly(ADP-ribosylation) protects maternally derived histones from proteolysis after fertilization.
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.
Morin
V
V
Department of Molecular Biology, Universidad de Concepción, Casilla 160-C, Concepción, Chile.
Diaz
F
F
Montecino
M
M
Fothergill-Gilmore
L
L
Puchi
M
M
Imschenetzky
M
M
D000818:Animals; D001704:Biopolymers; D005260:Female; D005306:Fertilization; D006657:Histones / Q000378:metabolism*; D011064:Poly Adenosine Diphosphate Ribose / Q000378:metabolism*; D012617:Sea Urchins
D001704:Biopolymers; D006657:Histones; D011064:Poly Adenosine Diphosphate Ribose