The ubiquitously expressed basic helix‐loop‐helix (bHLH) transcription factors E12 and E47, products of alternative splicing of the E2A/TCF3 gene, regulate diverse biological processes including cell growth, differentiation and development. To search for novel protein interactions for E12, we utilized the bHLH domain of E12 as a bait in yeast two‐hybrid screening. Yeast two‐hybrid, mammalian two‐hybrid, and co‐immunoprecipitation analyses demonstrate specific interaction of E12 with RANBP17, a novel member of the importin‐β superfamily; this interaction maps to the CRM1 homology region of RANBP17. Ectopic expression of RANBP17 leads to a ∼3‐fold increase in E2A/MyoD mediated transactivation of an E‐box regulated luciferase reporter gene. Interaction and transactivation studies also revealed similar functions for RANBP16/XPO7. Furthermore, ectopic expression of either RANBP16 or RANBP17 resulted in increased level of endogenous transcript for the cyclin‐dependent kinase inhibitor, p21Waf1/Cip1, a well‐characterized E2A target gene. Together, these biochemical and functional data reveal RANBP16 and RANBP17 as novel regulators of E2A protein action. J. Cell. Biochem. 111: 195–206, 2010. © 2010 Wiley‐Liss, Inc.