FOXP2 is a forkhead box-containing transcription factor with several recognizable sequence motifs. However, little is known about the FOXP2-associated proteins except for C-terminal binding protein (CtBP). In the present study, we attempted to isolate the FOXP2-associated protein with a yeast two-hybrid system using the C-terminal region, including the forkhead domain, as a bait probe, and identified protection of telomeres 1 (POT1) as a FOXP2-associated protein. Immunoprecipitation assay confirmed the association with FOXP2 and POT1. POT1 alone localized in the cytoplasm but co-localized with FOXP2 and the forkhead domain of FOXP2 in nuclei. However, both FOXP2 with mutated nuclear localization signals and (R553H) mutated forkhead, which is associated with speech-language disorder, prevented the nuclear translocation of POT1. These results suggest that FOXP2 is a binding partner for the nuclear translocation of POT1. As loss of POT1 function induces the cell arrest, the impaired nuclear translocation of POT1 in the developing neuronal cells may be associated with the pathogenesis of speech-language disorder with FOXP2(R553H) mutation. (C) 2011 Elsevier Inc. All rights reserved.