The evolutionarily conserved cell polarity protein Par3, a scaffold-like PDZ-containing protein, plays a critical role in the establishment and maintenance of epithelial cell polarity.Although the role of Par3 in establishing cell polarity in epithelial cells has been intensively explored, the function of Par3 in hematopoietic cells remains elusive.To address this issue,we generated GST-fusion proteins of Par3 PDZ domains.By cmbining the GST-pull-down approact with liq-uid chromatography-tandem mass spectrometry,we identi-fied 10 potential novel binding proteins of PDZ domains of Par3 in Jurkat cells(a T-cell line).The interaction of Par3 with three proteins-nuclear transport protein importin-αand proteasome activators PA28β and PA28γ-was con-firmed using in vitro binding assay,co-immunoprecipitation assay and immunofluorescence microscopy.Our results have the potential to uncover novel functions of the cell polarity protein Par3 in blood cells.