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. 2009 Jun;15(6):1121–1133. doi: 10.1261/rna.1195709

FIGURE 7.

FIGURE 7.

Vg1RBP phosphorylation correlates with its cortical detachment and solubilization of Vg1 mRNA. (A) The solubility of Vg1 mRNA in low salt buffer correlates with the phosphorylation of Vg1RBP. Stage VI oocytes were preincubated with 50 μM U0126 where indicated and then either injected with 50 nL 1.5 mg/mL MKK6-DD or exposed to progesterone. Control stage II and VI oocytes were incubated for the duration of the experiment without any treatment. After a 16-h incubation, oocytes were fractionated into soluble (S) and insoluble (P) fractions in low salt buffer. Equivalent proportions of RNA extracted from these fractions was then assayed for the presence of Vg1 (samples 1–13) or histone H3 (sample 14) mRNAs using nonsaturated RT-PCR. Arrows indicate the diagnostic PCR product. Brackets group samples that originated from the same experiment. (B) Vg1RBP phosphorylation correlates with its cortical release. Confocal images of stage VI oocytes (VI), oocytes matured by addition of progesterone in the absence or presence of 50 μM U0126 and stage VI oocytes injected with MKK6-DD (VI + MKK6-DD), stained with anti-Vg1RBP (A–D) and anti-GRP94 antibodies (visualizing the ER; A′–D′). Confocal images from equivalent subcortical layers near the vegetal pole are shown, except for the MKK6-injected oocytes where the slightly deeper layer to which the ER-Vg1RBP patches have sunk is shown. Scale bar: 20 μm.