Balancing act during development: lessons from a SUMO-less SF-1.

When a transcription factor is modified by small ubiquitin-like modifier (SUMO), this usually represses its transcriptional activity. In this issue of Developmental Cell, Lee et al. (2011) use a knockin mouse model to show that SUMO-less SF-1 binds and activates inappropriate targets, causing changes in cell fates and endocrine abnormalities.