Subcellular localization of the WT and mutant PCFT in stable transfectants. Immunohistochemical analysis of Myc-tagged WT (A) and mutant R113C PCFT (B) was performed with stably transfected RFC-null CHO cells using a Myc-tag–specific monoclonal antibody and 3,3′-diaminobenzidine as a chromogen. No specific immunostaining was observed in mock (C) and untransfected cells (D). Note the similar expression and the intense plasma localization (arrows) of the WT and mutant R113C PCFT.