Linking notch signaling, chromatin remodeling, and T-cell leukemogenesis

Intercellular communication that controls the developmental fate of multipo tent cells is commonly mediated by the Notch family of transmembrane recept ors. Specific transmembrane ligands activate Notch receptors on neighboring cells inducing the proteolytic liberation and nuclear translocation of the intracellular domain of Notch (N-IC); Nuclear N-IC associates with a trans criptional repressor known as C-promoter binding factor/RBP-J kappa; suppre ssor of hairless, or LAG-1, converting it from a repressor into an activato r. Through physical interactions with chromatin remodeling enzymes and pote ntially with components of the transcriptional machinery, N-IC activates ta rget genes that mediate cell fate decisions. As Notch1 is disrupted via a c hromosomal translocation in a subset of human T-cell leukemia, leading to a truncated polypeptide resembling N-IC, deregulated chromatin remodeling an d transcription may fuel uncontrolled cell proliferation in this hematopoie tic malignancy. This review summarizes the mechanics of Notch signaling and focuses on prospective molecular mechanisms for how constitutively active Notch might derail nuclear processes as an initiating step in T-cell leukem ogenesis. (C) 2001 Wiley-Liss, Inc.