A Schizosaccharomyces pombe temperature-sensitive mutant, rae1-1, was previously identified by us as being defective in nuclear export of Poly(A)+ RNA when grown at restrictive temperature. Here, we report the isolation of the human homologue of the S. pombe rae1 gene. The RAE1 genes are highly conserved in evolution in both structure and function. The human RAE1 cDNA, when expressed from the CMV-promoter, can suppress partially the temperature sensitivity of the rae1-1 mutant. This is also reflected by increased Poly(A)+ RNA export at a restrictive temperature. An epitope tagged human Rae1p localizes to both the nucleus and the cytoplasm in transiently transfected HeLa cells. We discuss the potential role of Rae1p in nuclear cytoplasmic trafficking in yeast and higher eukaryotic cells.