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General Comment |
Translational control plays a major role in the regulation of oocyte development (Mendez and Richter, 2001; de Moor et al., 2005; Piccioni et al., 2005; Haccard and Jessus, 2006). Maskin is thought to repress translation of cyclin B1 and c-Mos mRNA in Xenopus oocytes through its interaction with the RNA-binding protein CPEB [CPE (cytoplasmic polyadenylation element)-binding protein] and the cap-binding eIF-4E (eukaryotic initiation factor 4E) (de Moor and Richter, 1999; Stebbins-Boaz et al., 1999; Cao and Richter, 2002; Pascreau et al., 2005). Activation of translation of these mRNAs is mediated by cytoplasmic polyadenylation, a process initiated by phosphorylation of CPEB that leads to dissociation of the deadenylase PARN [poly(A) (polyadenylated RNA) ribonuclease] and polyadenylation of the mRNA by the default activity of the cytoplasmic poly(A) polymerase Gld-2 (de Moor and Richter, 1999; Barnard et al., 2004; Kim and Richter, 2006). Phosphorylation of maskin and the binding of PAB [poly(A)-binding protein] to the elongated poly(A) tail itself have been implicated in this translational activation (Cao and Richter, 2002; Barnard et al., 2005; Pascreau et al., 2005). In addition to its role in the meiotic cell cycle, maskin has been reported to play a role in the translational control of cyclin B1 in early embryonic cell division in Xenopus laevis (Groisman et al., 2000, 2002).
Maskin is a member of the TACC (transforming acidic coiled-coil) domain family of proteins, which share a highly conserved N-terminal domain of 200 amino acid residues. TACC proteins are localized at centrosomes and co-ordinate the formation of the mitotic spindle, at least in part through their interaction with members of the CKAP5 (cytoskeleton-associated protein 5) family, a group of microtubule plus-end stabilizing proteins (Gergely, 2002; Wiese and Zheng, 2006). Similar to other TACCs, the maskin protein is associated with centrosomes, both in embryos and tissue culture cells, and has a role in the organization of the mitotic spindle (Barnard et al., 2004; Huang and Richter, 2004; Kinoshita et al., 2005; O'Brien et al., 2005).
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