Adenylation and ADP-ribosylation in the mouse 1-cell embryo Available to Purchase

The incorporation of [³H]adenosine into cold trichloroacetic acid (TCA) insoluble material by the mouse 1-cell embryo has been studied. Incorporation of label was high immediately after fertilization, then decreased over the next 7 h with the sharpest decline occurring 3-5 h after fertilization. A small maximum was observed at the time of pronuclear DNA synthesis. Actinomycin D at a concentration which inhibited the cleavage of 1-cell embryos by 50 % had little effect on this incorporation, which in the period 1-6 h post-fertilization was shown by autoradiography to be confined to the ooplasm of the newly fertilized ovum. [³H]Adeno-sine and poly ([³H]A) were released from embryo RNA labelled 1-3 h after fertilization with [³H]adenosine by digestion with a mixture of ribonucleases A and T_x. The poly ([³H]A) segments were hydrolysed by alkali to 3’-[³H]AMP and [³H]adenosine ([³H]AMP/[³H]adeno-sine = 5/1), and by snake venom phosphodiesterase to 5’-[³H]AMP but very little [³H]adeno-sine. These results suggest that adenylation of RNA occurs soon after fertilization, that this is a cytoplasmic event, and that most of the newly synthesized poly ([³H]A) segments are joined to pre-existing poly (A) tracts. The unusual polynucleotide, poly (ADP-ribose), identi-fied by its resistance to alkali and the release of 2’-(5”-phosphoribosyl)-5’[³H]AMP on incu-bation with snake venom phosphodiesterase, was also found in the ribonuclease digest.