The transcription factor Elk-1 is a nuclear target of mitogen-activated protein kinases and regulates immediate early gene activation by extracellular signals. We show that Elk-1 is also conjugated to SUMO on either lysines 230, 249, or 254. Mutation of all three sites is necessary to fully block SUMOylation in vitro and in vivo. This Elk-1 mutant, Elk-1(3R), shuttles more rapidly to nuclei of Balb/C cells fused to transfected HeLa cells. Coexpression of SUMO-1 or -2 strongly reduces shuttling by Elk-1 without affecting that of Elk-1(3R), indicating that SUMOylation regulates nuclear retention of Elk-1. Accordingly, overexpression of Elk-1(3R) in PC12 cells, where cytoplasmic relocalization of Elk-1 has been linked to differentiation, enhances neurite extension relative to Elk-1. The effect of Elk-1, but not of the 3R mutant, was blocked upon cotransfection with SUMO-1 or -2 and enhanced by coexpression with mutant Ubc-9. Thus, SUMO conjugation is a novel regulator of Elk-1 function through the control of its nuclear-cytoplasmic shuttling.
SUMOylation regulates nucleo-cytoplasmic shuttling of Elk-1
Salinas, S.; Briancon-Marjollet, A.; Bossis, G.; Lopez, M. A.; Piechaczyk, M.; Jariel-Encontre, I.; Debant, A.; Hipskind, R. A.
J Cell Biol
2004-06-21 / vol 165 / pages 767-73
Humans; Animals; Cells, Cultured; Mice; Protein Transport; Mutagenesis, Site-Directed; Transfection; Proto-Oncogene Proteins/*metabolism; Transcription Factors/*metabolism; Hela Cells; Mice, Inbred BALB C; Recombinant Proteins/metabolism; Cell Nucleus/*physiology; ets-Domain Protein Elk-1; Cytoplasm/physiology; DNA-Binding Proteins/*metabolism; SUMO-1 Protein/*physiology