Aly (ally of AML-1 and LEF-1) is a component of the THO subcomplex of the TREX complex. The TREX complex specifically associates with spliced mRNA and not with unspliced pre-mRNA. Aly also functions as a chaperone and promotes the dimerization of transcription factors containing basic leucine zipper (bZIP) domains and thereby promotes transcriptional activation. Additionally, Aly plays a role in mRNA processing and export and may function as scaffold that mediates interactions between proteins and/or RNA. Aly is also part of the exon junction complex that remains associated with spliced mRNA and plays an important role in mRNA export and nonsense-mediated RNA decay. Aly directs mRNA derived from Herpes simplex virus intron-less genes to the NXF1-mediated export pathway [taken from the Universal Protein Resource (UniProt) www.uniprot.org/uniprot/ Q886V81].