SUMO and transcriptional repression: dynamic interactions between the MAP kinase and SUMO pathways.

SUMO modification of proteins is being increasingly linked with transcriptional repression. We recently demonstrated that SUMO modification also downregulates the transcriptional activity of the ETS-domain transcription factor Elk-1. However, as Elk-1 becomes activated through MAP kinase-mediated phosphorylation, the SUMO modification is lost, providing an elegant molecular switch that promotes the loss of repressive activities at the same time as permitting the recruitment of coactivator proteins. However, the mechanism by which SUMO promotes transcriptional repression remains enigmatic.