Le Goff Catherine, Laurent Véronique, Le Bon Kristell, Tanguy Gaëlle, Couturier Anne, Le Goff Xavier, Le Guellec René
CNRS UMR6061 Génétique et Développement, Université de Rennes 1, Groupe Développement Précoce, IFR140 GFAS, Faculté de Médecine, 2 avenue du Pr Léon Bernard, CS 34317, 35043 Rennes cedex, France.
Biol Cell. 2006 Dec;98(12):697-708. doi: 10.1042/BC20050095.
In Xenopus, during oocyte maturation and the segmentation period, cell cycle progression is independent of new transcription, but requires de novo translation. This suggests that the completion of oocyte maturation and then the rapid cell division period is controlled exclusively at a post-transcriptional level by specific gene products. To isolate these maternal genes, a differential screening of a Xenopus egg cDNA library was performed. Several cDNAs were isolated which correspond to mRNA polyadenylated in eggs and deadenylated in embryos, and these constitute the founders members of the Eg family of mRNAs.
We report here the characterization of Eg6 mRNA as a novel maternal gene expressed in Xenopus egg until gastrula stage. The Eg6 transcript is initially concentrated in the vegetal cytoplasm of the egg, and later the distribution of the transcript marks the posterior vegetal end of developing embryos. pEg6 is a multidomain protein with a kinase non-catalytic C-lobe domain of unknown function, a cluster of four WH2 (Wiskott-Aldrich syndrome protein homology 2) domains and a modified FYVE zinc-finger motif. The amino acid sequence of pEg6 is related to PEM-5 (posterior end mark-5), from an ascidian maternal mRNA, and spire, a Drosophila protein required to establish dorsal-ventral and anterior-posterior axes of polarity and recently described as an actin nucleation factor. In Xenopus and Schizosaccharomyces pombe cells pEg6 expression induces filamentous actin clusters and is associated with vesicular structure.
These data suggest that pEg6 acts as a vegetally localized factor contributing to the actin nucleation process during Xenopus early development.
在非洲爪蟾中，卵母细胞成熟和卵裂期的细胞周期进程不依赖于新的转录，但需要从头翻译。这表明卵母细胞成熟的完成以及随后的快速细胞分裂期仅在转录后水平由特定基因产物控制。为了分离这些母源基因，对非洲爪蟾卵cDNA文库进行了差异筛选。分离出了几个与卵中多聚腺苷酸化且胚胎中去腺苷酸化的mRNA相对应的cDNA，这些构成了Eg家族mRNA的创始成员。
我们在此报告Eg6 mRNA的特征，它是一种在非洲爪蟾卵中直至原肠胚期表达的新型母源基因。Eg6转录本最初集中在卵的植物极细胞质中，随后转录本的分布标记了发育中胚胎的植物极后端。pEg6是一种多结构域蛋白，具有功能未知的激酶非催化C叶结构域、一簇四个WH2（威斯科特-奥尔德里奇综合征蛋白同源2）结构域和一个修饰的FYVE锌指基序。pEg6的氨基酸序列与来自海鞘母源mRNA的PEM-5（后端标记-5）以及果蝇中建立背腹和前后极性轴所需的、最近被描述为肌动蛋白成核因子的spire相关。在非洲爪蟾和粟酒裂殖酵母细胞中，pEg6的表达诱导丝状肌动蛋白簇的形成并与囊泡结构相关。
这些数据表明pEg6作为一种植物极定位因子，在非洲爪蟾早期发育过程中有助于肌动蛋白成核过程。
