Role of ubiquitin protein ligase Ring2 in DNA damage of human bronchial epithelial cells exposed to benzo[a]pyrene.

Ubiquitylation of histones plays a pivotal role in DNA repair. The ubiquitin ligase Ring2 was recently shown to be the dominant ubiquitin ligase of histone H2A. In a series of experiments using the human bronchial epithelia cells (16HBE) and small interfering RNA (siRNA)-Ring2 cells exposed to benzo(a)pyrene (BaP), we measured dynamic changes in the levels of DNA damage, expressions of ubiquitinated histone H2A, and nucleotide excision repair (NER) subunit xeroderma pigmentosum (XP) groups A, C, and F (XPA, XPC, XPF). We found that in vitro exposure to BaP increased DNA damage in a time- and dose-dependent manner in 16HBE and siRNA-Ring2 cells. The results show that although decrease of Ring2 causes DNA hypersensitivity to BaP, the levels of XPA, XPC, and XPF were not affected. These results indicated that Ring2 may effect the DNA repair through other pathways but not through the expressions of NER protein.