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Fig. 8 Phylogenetic analysis for YB-1 and YB-2 in zebrafish and the hypothesis for roles of Ybx1 in follicle activation. (A) Chromosome synteny analysis of genes surrounding YB-1 among different organisms. (B) Synteny analysis of genes surrounding YB-2 genes. (C) Topology derived from ML and Bayesian analyses of YB-1 and YB-2 genes (amino acid sequence). The two numbers at a node represents Bootstrap value of ML and Bayesian analysis. The branch lengths are drawn according to ML tree. (D) Hypothetic model for roles of Ybx1 in PG-PV transition. As a key component of mRNPs, Ybx1 binds mRNAs in PG follicles together with other proteins such as PABP, DDX6, RAP55, and p54, stabilizing the messengers while suppressing their translation. At the transition from PG to PV, Ybx1 protein is massively degraded to release the mRNAs from the mRNPs for translation into a variety of regulatory proteins, resulting in follicle activation.