Fig. 9. Treatment of oocytes with LMB or mutation of the leucine-rich NES of Xp54 has little effect on nuclear export of mRNP particles. (A) Stage III/IV oocytes expressing T7-p54 were injected with 0.1 µCi of ³²P-CTP, and poly(A)⁺ RNP was extracted to assay radioactivity incorporated (columns) and T7-p54 present (immunoblot) in nuclei and cytoplasms after 16 and 28 hours. (B) Immunoprecipitation, with anti-T7 IgG, of poly(A)⁺ and poly(A)^– RNP extracted from cytoplasms of stage III/IV oocytes expressing T7-p54 and mutant T7-p54^NES– for 60 hours. In addition, poly(A)⁺ tails from cytoplasms of 50 oocytes expressing T7-p54^NES– were run on glycerol gradients, and sedimentation fractions were analysed by immunoblotting for the T7-tag. The sedimentation of T7-p54^NES– from 50 nuclei is also shown.