The mechanism of UV-radiation-induced EGF receptor (EGFR) internalization remains to be established. In the present study, we found UV-radiation-mediated internalization of the EGFR to be dependent on the cytoplasmic carboxy-terminal region. UV radiation was unable to induce internalization of EGFR carboxy-terminal truncation mutants where all or four of the five major autophosphorylation sites were missing (963- and 1028-EGFR, respectively). Mutational removal of serine residues 1046, 1047, 1057 and 1142 within the carboxy-terminal receptor region was also sufficient to abolish UV-radiation-induced internalization of the EGFR. Furthermore, the UV-radiation-induced internalization was abrogated for an EGFR mutated in tyrosine 1045 (Y1045F), the major c-Cbl binding site. However, UV radiation did not induce phosphorylation at tyrosine 1045, in contrast to the prominent phosphorylation induced by EGF. Our results suggest a mechanism for UV-radiation-induced internalization of EGFR involving a conformational change that is dependent on structural elements formed by specific serine and tyrosine residues in the carboxy-terminal domain. (C) 2004 by Radiation Research Society.