Nuclear Fusion of Signaling Pathways

There is often crosstalk between signal transduction pathways activated by different cytokines. In this issue, Nakashima and colleagues report on one way in which signaling pathways communicate. They show that the signaling pathways for two cytokines (LIF and BMP2), which are necessary for astrocyte differentiation, can interact synergistically through the binding of their transcription factor targets (STAT3 and Smad1, respectively) to a common transcriptional coactivator molecule called p300. Janknecht and Hunter comment on these findings in a Perspective and discuss ways in which the STAT3-Smad1-p300 complex brings about transcription of target genes.