ATR-dependent checkpoint modulates XPA nuclear import in response to UV irradiation

Abstract

In response to DNA damage, mammalian cells activate various DNA repair pathways to remove DNA lesions and, meanwhile, halt cell cycle progressions to allow sufficient time for repair. The nucleotide excision repair (NER) and the ATR-dependent cell cycle checkpoint activation are two major cellular responses to DNA damage induced by UV irradiation. However, how these two processes are coordinated in the response is poorly understood. Here we showed that the essential NER factor XPA (xeroderma pigmentosum group A) underwent nuclear accumulation upon UV irradiation, and strikingly, such an event occurred in an ATR (AtaxiaTelangiectasia mutated and RAD3-related)-dependent manner. Either treatment of cells with ATR kinase inhibitors or transfection of cells with small interfering RNA targeting ATR compromised the UV-induced XPA nuclear translocation. Consistently, the ATR-deficient cells displayed no substantial XPA nuclear translocation while the translocation remained intact in ATM (AtaxiaTelangiectasia mutated)-deficient cells in response to UV irradiation. Moreover, we found that ATR is required for the UV-induced nuclear focus formation of XPA. Taken together, our results suggested that the ATR checkpoint pathway may modulate NER activity through the regulation of XPA redistribution in human cells upon UV irradiation.

Hsp90 Inhibitor–Mediated Disruption of Chaperone Association of ATR with Hsp90 Sensitizes Cancer Cells to DNA Damage

“…ATR knockdown also increased IR-induced G 1 arrest but reduced the G 2 -M phase accumulation of HeLa cells in the cell cycle. In addition to its role in cell-cycle checkpoint, ATR also regulates DNA repair by inducing phosphorylation and causing intracellular redistribution of DNA repair proteins (4,39). Among the repair proteins phosphorylated by ATR are the BRCA1, WRN, BLM, FANCD2, and XPA proteins, which are involved in DNA repair by homologous recombination and nucleotide excision repair (4,39,(40)(41)(42)(43).…”

A Role for Checkpoint Kinase-Dependent Rad26 Phosphorylation in Transcription-Coupled DNA Repair in Saccharomyces cerevisiae

“…Such phosphorylation is required for normal levels of survival after UV treatment. ATR also controls nuclear import of XPA after DNA damage, but this is possibly independent of phosphorylation (64,65).…”

Other Proteins Interacting with XP Proteins

“…31 Thus, XPA may play a structural role in maintaining the pre-incision DNA bubble and positions the remaining NER factors, particularly XPF-ERCC1, 30 for final incisions while RPA may protect the undamaged strand (which will be used as the template for re-synthesis following incisions) from nuclease attack. 32 Other XPA interacting proteins include ATR (ATM and RAD3-Related), 33 a DNA damage checkpoint kinase of the phosphoinositide 3-kinase-like kinase (PIKK) family, XAB1 (XPA-binding protein 1) 34,35 and XAB2 (XPA-binding protein 2). 36,37 The interaction of XPA with ATR may be responsible for the rapid translocation of XPA from the cytoplasm to the nucleus in response to UV irradiation as this activity is dependent on ATR and can be abolished using either ATR inhibitors or siRNA-mediated knockdown of the kinase.…”

“…36,37 The interaction of XPA with ATR may be responsible for the rapid translocation of XPA from the cytoplasm to the nucleus in response to UV irradiation as this activity is dependent on ATR and can be abolished using either ATR inhibitors or siRNA-mediated knockdown of the kinase. 33 Although the mechanism of the translocation remains unclear, it is possible that the XPA binding protein XAB1, a cytoplasmic GTPase, may be involved. XAB1 binds to XPA via the nuclear localization signal located in the N-terminal region of XPA and is believed to help shuttle XPA though the nuclear pore by virtue of GTP hydrolysis.…”