Direct interaction of nucleoporin p62 with mRNA during its export from the nucleus.

Primary transcripts in eukaryotic cells undergo several processing steps within the nucleus, and resulting mature RNA molecules are selectively exported to the cytoplasm. Nucleo-cytoplasmic mRNA transport is an active process that likely involves RNA-protein interactions. To identify specific RNA-binding proteins, we designed a novel approach, which allows the analysis of interactions between mRNAs and proteins along the transport pathway. The method consists of inducing in vivo a covalent binding between nuclear proteins and microinjected mRNAs. Using such a procedure, we were able to detect a direct interaction between nucleoporin p62 with mRNA during export. The formation of the mRNA-p62 complex was inhibited by wheat-germ agglutinin, an inhibitor of mRNA export. Antibodies directed against p62 caused a substantial reduction in the rate of mRNA export from the nucleus.