FIGURE 2.

Selected aspects of polyadenylation by GLD‐2, TENT2, and Wispy in worms, frogs, and flies, respectively. (a) Polyadenylation by GLD‐2/GLD‐3 plays an important role in the mitosis‐to‐meiosis decision in the adult worm germline through the stabilization of gld‐1 mRNA, which encodes a repressor of mitosis‐promoting mRNAs. At the same time, GLD‐2/GLD‐3 activates repressed meiosis‐related mRNAs. Both events result in the switch from mitosis to meiosis. (b) In worms, GLD‐2 forms two separate complexes with RNA‐binding proteins. GLD‐2/GLD‐3 specifies spermatogenesis, and GLD‐2/RNP‐8 specifies oogenesis. (c) One of the proposed mechanisms of mRNA reactivation in Xenopus oocytes. In immature Xenopus oocytes, CPE‐containing mRNAs (UUUUUAU motif) are bound by CPEB and form a complex with CPSF, TENT2, PARN, ePABP, and Maskin that prevents assembly of the translation initiation complex and thus keeps mRNAs translationally repressed. Upon hormonal stimulation, CPEB is phosphorylated that leads to substantial rearrangements. PARN dissociates from the complex and allows TENT2 to extend poly(A) tails. As a result, ePABP binds to the newly elongated tails. eIF4G displaces Maskin from eIF4E and promotes formation of the translation initiation complex, initiating the translation of mRNAs. 40S, small subunit of the cytoplasmic ribosome; CPE, cytoplasmic polyadenylation element; CPEB, CPE‐binding protein; CPSF, cleavage and polyadenylation specificity factor; eIF3, eukaryotic initiation factor 3; eIF4, eukaryotic initiation factor 4; ePABP, embryonic poly(A) binding protein; PARN, poly(A)‐specific ribonuclease. (d) In the fruit fly, Wispy is recruited to its target mRNAs via interactions with various RNA‐binding proteins