Ephrin signaling is involved in various morphogenetic events, such as axon 
guidance, hindbrain segmentation, and angiogenesis. We conducted a yeast 
two-hybrid screen using the intracellular domain (ICD) of EphrinB1 to gain 
biochemical insightinto the function of the EphrinB1 ICD. We identified the 
transcriptional co-repressor xTLE1/Groucho as an EphrinB1 interacting protein. 
Whole-mount in situ hybridization of Xenopus embryos confirmed the 
co-localization of EphrinB1 and a Xenopus counterpart to TLE1, xTLE4, during 
various stages of development. The EphrinB1/xTLE4 interaction was confirmed by 
co-immunoprecipitation experiments. Further characterization of the interaction 
revealed that the carboxy-terminal PDZ binding motif of EphrinB1 and the SP 
domain of xTLE4 are required for binding. Additionally, phosphorylation of 
EphrinB1 by a constitutively activated fibroblast growth factor receptor 
resulted in loss of the interaction, suggesting that the interaction is 
modulated by tyrosine phosphorylation of the EphrinB1 ICD.