The Notch pathway is a short-range signaling mechanism between neighboring cells 
that results in changes in gene expression. Extracellular interactions between 
Notch receptors and ligands trigger proteolytic cleavage of the receptor Notch. 
Following cleavage, the freed intracellular domain of Notch (NotchIC) moves from 
the cytoplasm to the nucleus, engaging the DNA-binding transcription factor 
CBF-1, Su(H), Lag-1 (CSL)--the nuclear effector of the pathway. NotchIC, 
together with the transcriptional coactivator Mastermind, form a ternary complex 
with CSL that activates transcription from genes that are responsive to Notch 
signaling. Illuminating the molecular details that underlie formation of the 
transcriptionally active CSL-NotchIC-Mastermind ternary complex is key for 
understanding how genes are turned on in response to a Notch signal. Recently, 
several studies using biophysical and computational methods have scrutinized how 
the CSL-NotchIC-Mastermind ternary complex forms and the role individual domains 
play in this process. These detailed analyses have provided a wealth of 
molecular insights into the assembly of a Notch pathway active transcription 
complex but have also raised several intriguing, yet confounding questions. This 
review will focus on the findings of these recent biophysical studies and 
provide speculative models that address these unanswered questions.