未折叠蛋白反应（UPR）维持了哺乳动物细胞内质网（ER）的稳态、存活和生理功能。然而，细胞在生理或疾病状态下如何适应ER应激仍然大部分不清楚。在这里，通过基因组范围的CRISPR筛选，我们发现DNA损伤修复中涉及核内酶的RBBP8，在vitro中对ER应激下的ATF4激活起着重要作用。RNA-seq分析表明，RBBP8缺失导致细胞周期进程受阻，增殖缓慢，ATF4激活减弱，全局蛋白质合成减少。小鼠组织分析表明RBBP8在肝脏中高表达，并且其表达对tunicamycin腹腔注射引发的ER应激具有响应性。通过用腺病毒介导的shRNA抑制RBBP8的表达，我们发现肝细胞对tunicamycin（Tm）诱导的肝损伤、细胞死亡和ER应激反应呈抗性。为了研究RBBP8在调控ATF4活性中的病理学作用，我们发现与健康对照相比，RBBP8和ATF4在肝癌组织中高表达，并在肿瘤内的Ki67阳性增殖细胞中高表达。有趣的是，在vitro中过表达RBBP8促进了ER应激下的ATF4激活，并且RBBP8表达与肝癌组织中的ATF4表达呈阳性相关。我们的发现为细胞如何通过核与ER之间的相互作用适应ER应激以及肿瘤细胞如何在化疗或其他抗癌治疗下存活提供了新见解，提出了通过靶向DNA损伤修复、UPR或蛋白质合成治疗肝病的潜在策略。© 2023. the Author(s).

Unfolded protein response (UPR) maintains the endoplasmic reticulum (ER) homeostasis, survival, and physiological function of mammalian cells. However, how cells adapt to ER stress under physiological or disease settings remains largely unclear. Here by a genome-wide CRISPR screen, we identified that RBBP8, an endonuclease involved in DNA damage repair, is required for ATF4 activation under ER stress in vitro. RNA-seq analysis suggested that RBBP8 deletion led to impaired cell cycle progression, retarded proliferation, attenuated ATF4 activation, and reduced global protein synthesis under ER stress. Mouse tissue analysis revealed that RBBP8 was highly expressed in the liver, and its expression is responsive to ER stress by tunicamycin intraperitoneal injection. Hepatocytes with RBBP8 inhibition by adenovirus-mediated shRNA were resistant to tunicamycin (Tm)-induced liver damage, cell death, and ER stress response. To study the pathological role of RBBP8 in regulating ATF4 activity, we illustrated that both RBBP8 and ATF4 were highly expressed in liver cancer tissues compared with healthy controls and highly expressed in Ki67-positive proliferating cells within the tumors. Interestingly, overexpression of RBBP8 in vitro promoted ATF4 activation under ER stress, and RBBP8 expression showed a positive correlation with ATF4 expression in liver cancer tissues by co-immunostaining. Our findings provide new insights into the mechanism of how cells adapt to ER stress through the crosstalk between the nucleus and ER and how tumor cells survive under chemotherapy or other anticancer treatments, which suggests potential therapeutic strategies against liver disease by targeting DNA damage repair, UPR or protein synthesis.© 2023. The Author(s).