The RNA binding protein HuB was ectopically expressed in 3T3-L1 preadipocytes and localized primarily to the nucleus, as the cells differentiated HuB redistributed to the cytosol and on analysis localized to the dense polysomes. Electron micrographs confirm association of HuB with the ribosomes in the adipocytes consistent with a proposed role in control of translation and mRNA stability. Examination of the expression of C/EBP-beta in the cells expressing HuB relative to the parental 3T3-L1 adipocytes demonstrated an alteration in the LAP to LIP ratio. The data support a role for endogenous Hu proteins in the differentiation process, potentially affecting the rate of differentiation by controlling the concentration of the dominant negative transcription inhibitor, LIP. (C) 2003 Elsevier Inc. All rights reserved.