FRET analysis of interactions between actin and exon-exon-junction complex proteins in early mouse embryos

Spatial interactions between nuclear actin and some proteins of the exon-exon junction complex (EJC) have been demonstrated in the nuclei of early mouse embryos by using Forster resonance energy transfer (FRET). FRET has been registered for the pairs actin-Y14, actin–Aly/REF and actin–NXF1/TAP in nucleoplasmic, irregularly shaped zones and in nucleolus precursor bodies (NPBs). We suggest that FRET signals in the nucleoplasm correspond to the bordering zone of transcriptionally active chromatin. Detection of FRET in NPBs indicates that the list of NPB functions is broader than has been assumed to date. The FRET pattern, typical for transcriptionally active embryos, is retained after treatment with DRB (a transcription inhibitor). Spatial interactions between actin and Y14 have been found to occur in an RNA-dependent manner. Our data thus suggest that nuclear actin is directly involved in mRNA export in early mouse embryos.