Chromatin retention of DNA damage sensors DDB2 and XPC through loss of p97 segregase causes genotoxicity

Abstract

DNA damage recognition subunits like DDB2 and XPC protect the human skin from ultraviolet (UV) light-induced genome instability and cancer, as demonstrated by the devastating inherited syndrome xeroderma pigmentosum. Here, we show that the beneficial DNA repair response triggered by these two genome caretakers critically depends on a dynamic spatiotemporal regulation of their homeostasis. The prolonged retention of DDB2 and XPC in chromatin, due to a failure to readily remove both recognition subunits by the ubiquitin-dependent p97/VCP/Cdc48 segregase complex, leads to impaired DNA excision repair of UV lesions. Surprisingly, the ensuing chromosomal aberrations in p97-deficient cells are alleviated by a concomitant down regulation of DDB2 or XPC. Also, genome instability resulting from an excess of DDB2 persisting in UV-irradiated cells is prevented by concurrent p97 over-expression. Our findings demonstrate that DNA damage sensors and repair initiators acquire unexpected genotoxic properties if not controlled by timely extraction from chromatin.

Valosin-containing Protein (VCP)/p97 Segregase Mediates Proteolytic Processing of Cockayne Syndrome Group B (CSB) in Damaged Chromatin

“…UVR incited a reduction of CSB and DDB2 in chromatin, which was blocked by DBeQ or MG132 treatment. The examination of DDB2 confirmed the involvement of VCP/p97 in promoting the degradation of chromatin bound DDB2 (13). As expected, the nuclear protein ORC2 was detected in the nucleoplasmic fraction and enriched in the soluble chromatin fraction.…”

“…Although accumulation of Myc-VCP/p97 can be seen at DNA damage spots generated by micropore UV irradiation at 100 J/m 2 ( Fig. 1S) (13,32), the use of Myc-tagged EQ-VCP/p97 and the higher doses gave a better image quality, which is necessary for quantitative analysis. As shown in Fig.…”

“…It has been observed that VCP/p97 mediates the extraction of Aurora B kinase from mitotic chromosomes (11) and the L3MBTL1 repressor from DNA double-strand breaks (12). Recently VCP/ p97 has been shown to participate in the extraction and removal of early damage recognition factors, DDB2 and XPC, from DNA damage sites (13). Failure to remove DDB2 and XPC impairs the excision repair of photolesions and thereby leads to chromosome aberrations.…”

The VCP/p97 system at a glance: connecting cellular function to disease pathogenesis

“…VCP/p97 dissociates proteins from chromatin, either for their degradation or for recycling, to modulate the dynamics of chromatin regulators, and the list of substrates that are regulated in this way is growing Vaz et al, 2013). Currently, prominent examples that illustrate the diversity of functions include the extraction of Aurora B kinase from mitotic chromosomes, degradation of CDT1 and stalled RNA polymerase II in response to UV-induced DNA damage or degradation of DDB2 as part of nucleotide excision repair (Ramadan et al, 2007;Dobrynin et al, 2011;Raman et al, 2011;Verma et al, 2011;Puumalainen et al, 2014). In response to double-strand breaks, VCP/p97 removes L3MBTL1 and unidentified K48-linked ubiquitin conjugates from damaged sites to orchestrate DNA repair and facilitates CDC25A degradation to enforce the G2/M checkpoint (Acs et al, 2011;Meerang et al, 2011;Riemer et al, 2014).…”

Effects of single water molecule on proton transfer reaction in uracil dimer cation

“…[1][2][3][4][5] If DNA base pair is ionized by the irradiation, a proton is transferred into the neighbored base along the hydrogen bond, while a defect is formed in the damaged DNA. The defect leads to replication and transcriptional errors in DNA.…”