Fig. 3.

Repression of nanos1 in oocytes does not depend on trans-acting factors. (A) Xenopus oocytes were injected with either nanos1-Myc or Myc-nanos1 transcripts and incubated at 18°C overnight. Translation products were detected by blotting (IB) with anti-Myc antibody. (B,C) nanos1 repression is not relieved in vivo by excess levels of nanos1 mRNA. Oocytes were injected with increasing amounts of synthetic capped nanos1 (B) or capped Myc-nanos1 (C) as indicated, incubated at 18°C overnight, and products analyzed by blotting with anti-Nanos1 antibodies. Myc-nanos1 served as a positive control. Note that nanos1 repression was not relieved at any concentration of nanos1 mRNA. (D) Histogram showing the results from two independent in vitro competition experiments. Twenty-five nanograms of capped nanos1 transcripts were translated for 90 minutes at room temperature in oocyte extract containing [³⁵S]methionine. Uncapped nanos1 transcripts were added to the translation mix in increasing amounts as indicated. As positive controls, 25 ng of capped nanos1 and β-globin RNAs were translated in reticulocyte lysates and oocyte extracts, respectively. Even in the presence of an 80-fold excess of uncapped nanos1 RNA, repression was not relieved.