Bi-polarized translation of ascidian maternal mRNA determinant pem-1 associated with regulators of the translation machinery on cortical Endoplasmic Reticulum (cER)

Alexandre Paix, Phuong Ngan Le Nguyen, Christian Sardet

Research output: Contribution to journalArticle

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.

Original languageEnglish (US)
Pages (from-to)211-226
Number of pages16
JournalDevelopmental biology
Volume357
Issue number1
DOIs
StatePublished - Sep 1 2011

Keywords

  • Ascidian
  • Cortex
  • Determinant mRNA
  • Endoplasmic reticulum
  • Fertilization
  • Translation initiation

ASJC Scopus subject areas

  • Molecular Biology
  • Developmental Biology
  • Cell Biology

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