A low content of ERCC1 and a 120 kDa protein is a frequent feature of group F xeroderma pigmentosum fibroblast cells.

The ERCC1 protein has been predicted to form part of a tight complex with a protein partner, the yet-unidentified XPF/ERCC4 protein, in normal human cells. We used an anti-ERCC1 antibody to detect the complex by immunoprecipitation and immunoblotting. The amount of ERCC1 protein expressed in five different XP-F cell strains was 1/ 5-1/34 of that of the protein in normal and XP cell strains representing other complementation groups. A 120 kDa protein was co-immunoprecipitated with ERCC1 by the anti-ERCC1 antibody, and the amount of the 120 kDa protein in XP-F cell strains was 1/5-1/8 of that of the protein in normal and XP cell strains representing other complementation groups. The XPA protein was not co-immunoprecipitated with ERCC1 in any cell strain. These results demonstrate that a low level of ERCC1 and the 120 kDa protein is a frequent feature of XP-F cell extracts and that a lower amount of a complex between these proteins occurs in XP-F cells than in normal cells.