Nucleocytoplasmic shuttling of endocytic proteins

Many cellular processes rely on the ordered assembly of macromolecular stru ctures. Here, we uncover an unexpected link between two such processes, end ocytosis and transcription. Many endocytic proteins, including eps15, epsin 1, the clathrin assembly Lymphoid myeloid leukemia (CALM), and alpha -adapt in, accumulate in the nucleus when nuclear export is inhibited. Endocytosis and nucleocytoplasmic shuttling of endocytic proteins are apparently indep endent processes, since inhibition of endocytosis did not appreciably alter nuclear translocation of endocytic proteins, and blockade of nuclear expor t did not change the initial rate of endocytosis. In the nucleus, eps15 and CALM acted as positive modulators of transcription in a GAL4-based transac tivation assay, thus raising the intriguing possibility that some endocytic proteins play a direct or indirect role in transcriptional regulation.