Figure 2.

Mammalian Musashi1 functionally compensates for Xenopus Musashi in mediating cell cycle progression in Xenopus oocytes. (A) Progesterone-stimulated cell cycle progression is assayed as percent of oocytes that undergo germinal vesicle breakdown (maturation). Knockdown of Musashi function in Xenopus oocytes, through injection of antisense oligonucleotides targeting the mRNAs encoding endogenous Musashi1 and Musashi2 isoforms, results in inhibition of cell cycle progression (Msi AS). All procedures have been previously described in reference ²⁰. Injection of mRNA (23 ng/oocyte) encoding mammalian Musashi1 rescues cell cycle progression in Musashi antisense-treated oocytes (Msi AS + mMsi). Over 50 oocytes were scored for each condition and error bars represent SEM from three independent experiments. Injection of control antisense oligonucleotide did not block cell cycle progression (Con AS). The rescue of cell cycle progression was highly significant (p < 0.005, Student's t-test). (B) Control antisense (Con AS) or Musashi antisense (Msi AS) oligonucleotide injected oocytes were treated with (+) or without (−) progesterone and analyzed for polyadenylation of endogenous cyclin B5 mRNA by RNA ligation-coupled PCR as described in reference ²⁰. A progesterone-dependent heterogeneous increase in the size of the mRNA population in Con AS oocytes and Msi AS oocytes injected with mammalian Musashi1 (Msi AS + mMsi) is indicative of polyadenylation and translational activation (bracketed).