A DDB2 mutant protein unable to interact with PCNA promotes cell cycle progression of human transformed embryonic kidney cells

DNA damage binding protein 2 (DDB2) is a protein involved in the early step of DNA damage recognition of the
nucleotide excision repair (NER) process. Recently, it has been suggested that DDB2 may play a role in DNA replication,
based on its ability to promote cell proliferation. We have previously shown that DDB2 binds PCNA during NER, but also
in the absence of DNA damage; however, whether and how this interaction influences cell proliferation in not known. In
this study, we have addressed this question by using HEK293 cell clones stably expressing DDB2Wt protein, or a mutant
form (DDB2Mut) unable to interact with PCNA. We report that overexpression of the DDB2Mut protein provides a
proliferative advantage over the wild type form, by influencing cell cycle progression. In particular, an increase in the number of S-phase cells, together with a reduction in p21CDKN1A protein level, and a shorter cell cycle length, has been
observed in the DDB2Mut cells. These results suggest that DDB2 influences cell cycle progression thanks to its
interaction with PCNA.