Mouse development with a single E2F activator

The E2F family is a family of proteins, some of which act as transcription activators and others as repressors. Here Shih-Yin Tsai et al. tested why there is such genetic complexity by inactivating the entire subset of activators singly or in combination in mice. They show that E2f3a is sufficient to support mouse embryonic and postnatal development. However, expression of E2f3b or E2f1 from the E2f3a locus suppressed all the postnatal phenotypes associated with the inactivation of E2f3a. They conclude there is functional redundancy among activators and that the requirement for E2f3a during postnatal development is dictated by its regulatory sequences, not by its protein function. These findings provide a molecular basis for the observed specificity among E2F activators during development.