title: Bi-polarized translation of ascidian maternal mRNA determinant pem-1 associated with regulators of the translation machinery on cortical Endoplasmic Reticulum (cER).
abstract: Polarized cortical mRNA determinants such as maternal macho-1 and pem-1 in ascidians, like budding yeast mating factor ASH1 reside on the cER-mRNA domain a subdomain of cortical Endoplasmic Reticulum(ER) and are translated in its vicinity. Using high resolution imaging and isolated cortical fragments prepared from eggs and embryos we now find that macho-1 and pem-1 RNAs co-localize with phospho-protein regulators of translation initiation (MnK/4EBP/S6K). Translation of cortical pem-1 RNA follows its bi-polarized relocalization. About 10 min after fertilization or artificial activation with a calcium ionophore, PEM1 protein is detected in the vegetal cortex in the vicinity of pem-1 RNA. About 40 min after fertilization-when pem-1 RNA and P-MnK move to the posterior pole-PEM1 protein remains in place forming a network of cortical patches anchored at the level of the zygote plasma membrane before disappearing. Cortical PEM1 protein is detected again at the 4 cell stage in the posterior centrosome attracting body (CAB) region where the cER-mRNA domain harboring pem-1/P-MnK/P-4EBP/P-S6K is concentrated. Bi-polarized PEM1 protein signals are not detected when pem-1 morpholinos are injected into eggs or zygotes or when MnK is inhibited. We propose that localized translation of the pem-1 RNA determinant is triggered by the fertilization/calcium wave and that the process is controlled by phospho-protein regulators of translation initiation co-localized with the RNA determinant on a sub-domain of the cortical Endoplasmic Reticulum.
authors: Université Pierre et Marie Curie and Centre National de la Recherche Scientifique, BioMarCell, UMR BioDev, Observatoire Océanologique, Villefranche-sur-mer, France.
authors: Alexandre
authors: A
authors: Paix
authors: Phuong Ngan
authors: PN
authors: Le Nguyen
authors: Christian
authors: C
authors: Sardet
mesh_terms: D000818:Animals; D016764:Cell Polarity / Q000502:physiology; D018385:Centrosome / Q000378:metabolism; D004330:Drosophila / Q000196:embryology; D004625:Embryo, Nonmammalian / Q000378:metabolism; D004721:Endoplasmic Reticulum / Q000378:metabolism*; D014176:Protein Biosynthesis / Q000502:physiology*; D012333:RNA, Messenger / Q000378:metabolism; D023121:RNA, Messenger, Stored / Q000378:metabolism*; D014157:Transcription Factors / Q000378:metabolism; D014561:Urochordata / Q000235:genetics* / Q000378:metabolism; D014981:Xenopus / Q000196:embryology
chemical_list: D012333:RNA, Messenger; D023121:RNA, Messenger, Stored; D014157:Transcription Factors