In C. elegans, tra-2 mRNA nuclear export is controlled by a 3′UTR element, the TRE. In the absence of TRA-1, the TRE retains tra-2 mRNA in the nucleus. The binding of TRA-1 to the 3′UTR overcomes this retention resulting in export of a TRA-1/tra-2 mRNA complex. Here, we find that, unlike most mRNAs, tra-2 mRNA exits the nucleus via an alternative pathway to NXF-1 that requires CRM1 activity. Inhibition of export by NXF-1 depends upon the TRE, CeNXF-2, CeREF-1, and CeREF-2. Removal of the TRE or any one of these factors results in export of tra-2 by NXF-1. NXF-2 and REF-1 specifically bind the TRE, suggesting that they directly control tra-2 mRNA export. Furthermore, choice of proper export pathway affects tra-2 translational control. Therefore, tra-2 mRNA export is highly regulated and plays an important role in development by regulating the activity of tra-2 mRNA in the cytoplasm.
Current address: Department of Molecular and Cellular Biology, University of Arizona, Life Sciences South-Lab 404, 1007 East Lowell Street, Tucson, Arizona 85721.
