A cellular cofactor for the constitutive transport element of type D retrovirus.

A human nuclear protein that specifically interacts with the constitutive transport element (CTE) of simian retrovirus was identified as adenosine 5'-triphosphate-dependent RNA helicase A. This protein could bind to functional CTE but not to inactive CTE mutants. The interaction of helicase A with CTE was distinct from previously described helicase activity of this protein. Helicase A shuttled from the nucleus to the cytoplasm in the presence of a transcription inhibitor or in cells transiently overexpressing CTE-containing RNA. In vivo colocalization of helicase A and CTE was observed in experiments that combined in situ hybridization and immunostaining. These results suggest that helicase A plays a role in the nuclear export of CTE-containing RNA.