Retention of p63 in an ER-Golgi intermediate compartment depends on the presence of all three of its domains and on its ability to form oligomers

The results with the PPD and A24-101PPD constructs together with the mutational analysis of the p63 cytoplasmic tail establish that the transmembrane domain of p63 is not sufficient for its localization. To determine whether this domain is a necessary component, we created an additional chimera that combines a p63 cytoplasmic tall that has amino acids 24-101 deleted with the transmembrane domain of DPPIV and the lumenal part of p63 (A24-101PDP; p63 with deletion of amino acids 24-101 cytoplasmic, DPPIV transmembrane, p63 lumenal; Fig. 9 ). Immunofluorescence microscopy of transfected cells showed that the internal distribution of A24-101PDP is very similar to p63wt (Fig. 10 i) . Unlike p63wt, however, some A24-101PDP molecules were detected on the plasma membrane in unpermeabilized cells (Fig. 10 j) . The intensity of this cell surface staining was fainter than that of DPPIVwt or any of the other chimeric constructs. Thus, while the transmembrane domain contributes to the complete intracellular retention of p63, it appears to be less important for the overall localization than its cytoplasmic and lumenal counterparts.