期刊名称：Proceedings of the National Academy of Sciences
印刷版ISSN：0027-8424
电子版ISSN：1091-6490
出版年度：2022
卷号：119
期号：9
DOI：10.1073/pnas.2111404119
语种：English
出版社：The National Academy of Sciences of the United States of America
摘要：Significance
Stress response pathways, such as the DNA damage response and the UPR, are critical in the etiology and treatment of cancer and other chronic diseases. Knowledge of an interplay between ER stress and genome damage repair is emerging, but evidence linking defective DNA repair and impaired ER stress response is lacking. Here, we show that AAG is necessary for UPR activation in response to alkylating agents. AAG-deficient mice and human cancer cells are impaired in alkylation-induced UPR. Strikingly, this defect can be complemented by an AAG variant defective in glycosylase activity. Our studies suggest that AAG has noncanonical functions and identify AAG as a point of convergence for stress response pathways. This knowledge could be explored to improve cancer treatment.
Alkylating agents damage DNA and proteins and are widely used in cancer chemotherapy. While cellular responses to alkylation-induced DNA damage have been explored, knowledge of how alkylation affects global cellular stress responses is sparse. Here, we examined the effects of the alkylating agent methylmethane sulfonate (MMS) on gene expression in mouse liver, using mice deficient in alkyladenine DNA glycosylase (Aag), the enzyme that initiates the repair of alkylated DNA bases. MMS induced a robust transcriptional response in wild-type liver that included markers of the endoplasmic reticulum (ER) stress/unfolded protein response (UPR) known to be controlled by XBP1, a key UPR effector. Importantly, this response is significantly reduced in the
Aag knockout. To investigate how AAG affects alkylation-induced UPR, the expression of UPR markers after MMS treatment was interrogated in human glioblastoma cells expressing different AAG levels. Alkylation induced the UPR in cells expressing AAG; conversely,
AAG knockdown compromised UPR induction and led to a defect in XBP1 activation. To verify the requirements for the DNA repair activity of AAG in this response,
AAG knockdown cells were complemented with wild-type
Aag or with an
Aag variant producing a glycosylase-deficient AAG protein. As expected, the glycosylase-defective Aag does not fully protect
AAG knockdown cells against MMS-induced cytotoxicity. Remarkably, however, alkylation-induced XBP1 activation is fully complemented by the catalytically inactive AAG enzyme. This work establishes that, besides its enzymatic activity, AAG has noncanonical functions in alkylation-induced UPR that contribute to cellular responses to alkylation.
关键词：enalkylating agentsunfolded protein responseDNA damageER stressbase excision repair
