A short conserved motif in ALYREF directs cap- and EJC-dependent assembly of export complexes on spliced mRNAs.

The export of messenger RNAs (mRNAs) is the final of several nuclear posttranscriptional steps of gene expression. The formation of export-competent mRNPs involves the recruitment of export factors that are assumed to facilitate transport of the mature mRNAs. Using in vitro splicing assays, we show that a core set of export factors, including ALYREF, UAP56 and DDX39, readily associate with the spliced RNAs in an EJC (exon junction complex)- and cap-dependent manner.

CWC22 connects pre-mRNA splicing and exon junction complex assembly.

The exon junction complex (EJC) is a key regulator of posttranscriptional mRNA fate and binds to mRNA during splicing. Although the composition of EJCs is well understood, the mechanism mediating splicing-dependent EJC assembly and the factor(s) recruiting the EJC remain elusive. Here, we identify CWC22 as an essential splicing factor that is required for EJC assembly.