Western blot using POU5F1 polyclonal antibody (Cat # PAB10296) shows detection of endogenous POU5F1 in mouse embryonic fibroblast (MEF) cell lysate (lane 1) and HeLa nuclear extract (HN) (lane 2). The band at ~39 kDa (arrowhead) corresponds to POU5F1. After transfer, the membrane was blocked with 5% BSA. Primary antibody was used at a 1 : 1,000 dilution in PBS containing 5% BSA. The specificity of the antibody was confirmed by peptide competition which blocks reaction of the antibody with POU5F1 (lanes 3 and 4, respectively).