Aspects of ADP-ribose metabolism during the embryonic development of Xenopus laevis
i30/2/2667 Aspects of ADP-ribose metabolism during the embryonic development of Xenopus laevis. MacDermott, G.1. Attempts were made to investigate the synthesis of poly (ADP-ribose)•in v vo in developing embryos and oocytes of Xenopus laovis. Fertilized eggs were microinjected with (3H) or (14C) NAD+. The label appeared to be more readily catabolized to AMP, ADP and ATP than to ADPribose.2. Vitellogenic females were labelled with the non-specific precursor, 32Pi. Histones were isolated from labelled embryos and oocytes. Contamination of the histones with non-specifically bound 32 Pi and ribonucleotides were extensive. It proved very difficult to remove the contaminating material completely.3. Oocytes undergoing maturation were labelled with (3H) adenosine, a non-specific precursor. Inconclusive evidence suggested that a small amount of radioactivelylabelled poly(ADP-ribose) was synthesized.4. ADP-ribosylation of the nuclear his tones in vitro throughout early embryonic development was investigated. The following findings were made:(1) Longer poly(ADP-ribose) chains were synthesized asdevelopment proceeded.(ii) Poly(ADP-ribose) chains initiated in vivo werecovelently elongated in vitro.(iii) The pattern of ADP-ribosylation was dependent on NAD+concentration. Incubation of isolated nuclei with7, pM or 4 mM NAD+.resulted in the synthesis ofI180poly(ADP-ribose) chains of similar lengths, but differences were found in the relative proportions of the various poly(ADP-ribose) chains.(iv) A decline in the amount of ADP-ribose attached to the nuclear histones occurred as development progressed.(v) Initiation of poly(ADP-ribose) chain synthesis in vitro was demonstrated.