Figure 4.
VHL promotes cytoplasmic localization of Sima. (A) In embryos expressing a VHL RNAi transgene (VHLi), Sima was more nuclear than in wild-type (WT) controls at all tested oxygen levels after stage 13 (p < 10−4; n > 40). ■, nuclear; ▩, ubiquitous; and □, cytoplasmic. (B) Sima nuclear export assay upon reoxygenation, in embryos expressing VHLi, reveals that Sima export was severely impaired (Kaplan-Meier; p < 10−4; n > 30). (C) Overexpression of Drosophila VHL increased Sima cytoplasmic localization at all tested oxygen levels throughout embryogenesis with the exception of those conditions where in the wild-type controls, Sima was already fully cytoplasmic (p < 10−2; n > 40). (D) Nuclear export of Sima is more efficient in embryos overexpressing VHL. Sima nuclear export assay similar to the one depicted in B (Kaplan-Meier; p < 10−4; n > 30). (E) A mutagenized version of Sima in which proline 850 was replaced by an alanine (SimaP850A) was insensitive to VHL overexpression, remaining totally nuclear even in normoxia (n > 40).