A novel role for Celf1 in vegetal RNA localization during Xenopus oogenesis

Abstract

The localization of certain mRNAs to the vegetal cortex of Xenopus oocytes is of crucial importance for germ cell development and early embryonic patterning. Vegetal RNA localization is mediated by cis-acting RNA localization elements (LE). Several proteins assemble on the RNA LE and direct transport to the vegetal cortex. Although a number of localization RNP components have been identified, their full composition is unknown. In an RNA affinity purification approach, using the dead end 1 (dnd1) RNA LE, we identified Xenopus Celf1 as a novel component of vegetal localization RNP complexes. Celf1 is part of an RNP complex together with known vegetal localization factors and shows specific interactions with LEs from several but not all vegetally localizing RNAs. Immunostaining experiments reveal co-localization of Celf1 with vegetally localizing RNA and with known localization factors. Inhibition of Celf1 protein binding by localization element mutagenesis as well as Celf1 overexpression interfere with vegetal RNA localization. These results argue for a role of Celf1 in vegetal RNA localization during Xenopus oogenesis.

T-cell internal antigen 1 counteracts somatic RNA degradation during early Xenopus embryogenesis

“…As reported before (Bauermeister et al, 2015), Cy3-dnd1-LE becomes enriched at the vegetal cortex and in granular structures in the cytoplasm of the vegetal hemisphere (Fig. 2C).…”

“…Tia1 was identified in the context of an attempt aiming at the identification of novel dnd1-LE binding proteins in X. laevis oocytes, making use of an RNA affinity purification approach (Bauermeister et al, 2015). Our results reveal that, in X. laevis oocytes, Tia1 is part of one and the same RNP complex together with other proteins known to function in vegetal RNA localization.…”

“…1). Celf1 and Ptbp1 were previously shown to be components of localization RNPs in X. laevis oocytes and served as controls (Bauermeister et al, 2015;Cote et al, 1999). Tia1 co-precipitates other known localization components such as Igf2bp3, Stau1, Hnrnpab and Elav-like proteins, indicating that Tia1 could indeed be a component of vegetal localization RNP complexes in X. laevis oocytes.…”

“…Using an RNP reconstitution/purification approach combined with tandem mass spectrometry (Bauermeister et al, 2015), we identified X. laevis Tia1 as one of the proteins that specifically interact with the LE of the vegetally localizing dnd1 mRNA using extracts from stage III/IV oocytes. Tia1 and the highly similar Tiar (Tia-related) represent the TIA-1 family of ARE (AU-rich element) binding proteins (Dember et al, 1996).…”

“…Tia1 was identified by an RNA affinity approach using the dnd1-LE (Bauermeister et al, 2015). In order to analyze if Tia1 directly binds to the dnd1-LE and/or to other vegetal LEs, an in vitro interaction assay was performed.…”