Comparative Oncology Laboratory, Schools of Veterinary Medicine and Medicine, UC Davis, California, Davis, USA.
Department of Animal Science and Technology, Sichuan Agricultural University, Ya'an, China.
Cell Death Dis. 2023 Jan 11;14(1):14. doi: 10.1038/s41419-022-05529-7.
TP73 is expressed as multiple N- and C-terminal isoforms through two separate promoters or alternative splicing. While N-terminal p73 isoforms have been well studied, very little is known about p73 C-terminal isoforms. Thus, CRISPR was used to delete TP73 Exon13 (E13-KO) to induce p73α to p73β isoform switch. We showed that E13-KO led to decreased cell proliferation and migration and sensitized cells to ferroptosis, which can be reverted by knockdown of TAp73β in E13-KO cells. To understand the biological function of p73β in vivo, we generated a mouse model in that the Trp73 E13 was deleted by CRISPR. We showed that p73α to p73β isoform switch led to increased cellular senescence in mouse embryonic fibroblasts. We also showed that E13-deficient mice exhibited shorter life span and were prone to spontaneous tumors, chronic inflammation and liver steatosis as compared to WT mice. Additionally, we found that the incidence of chronic inflammation and liver steatosis was higher in E13-deficient mice than that in Trp73-deficient mice, suggesting that p73β is a strong inducer of inflammatory response. Mechanistically, we showed that TAp73β was able to induce cysteine dioxygenase 1 (CDO-1), leading to cysteine depletion and subsequently, enhanced ferroptosis and growth suppression. Conversely, knockdown of CDO-1 was able to alleviate the growth suppression and ferroptosis in E13-KO cells. Together, our data suggest that at a physiologically relevant level, TAp73β is a strong inducer of growth suppression but insufficient to compensate for loss of TAp73α in tumor suppression due to aberrant induction of inflammatory response and liver steatosis.
TP73 通过两个独立的启动子或选择性剪接表达为多个 N 端和 C 端异构体。虽然 N 端 p73 异构体已得到充分研究，但对 p73 C 端异构体知之甚少。因此，我们使用 CRISPR 技术删除 TP73 外显子 13（E13-KO）以诱导 p73α 到 p73β 异构体转换。我们发现 E13-KO 导致细胞增殖和迁移减少，并使细胞对铁死亡敏感，而 E13-KO 细胞中 TAp73β 的敲低可逆转这种情况。为了了解 p73β 在体内的生物学功能，我们使用 CRISPR 技术在小鼠模型中删除了 Trp73 E13。我们发现 p73α 到 p73β 异构体转换导致小鼠胚胎成纤维细胞中细胞衰老增加。我们还发现，与 WT 小鼠相比，E13 缺失小鼠的寿命更短，更容易自发产生肿瘤、慢性炎症和肝脂肪变性。此外，我们发现 E13 缺失小鼠的慢性炎症和肝脂肪变性发生率高于 Trp73 缺失小鼠，这表明 p73β 是炎症反应的强诱导剂。机制上，我们发现 TAp73β 能够诱导半胱氨酸双加氧酶 1（CDO-1），导致半胱氨酸耗竭，进而增强铁死亡和生长抑制。相反，CDO-1 的敲低能够缓解 E13-KO 细胞中的生长抑制和铁死亡。总之，我们的数据表明，在生理相关水平下，TAp73β 是生长抑制的强诱导剂，但不足以弥补由于异常诱导炎症反应和肝脂肪变性而导致的 TAp73α 在肿瘤抑制中的缺失。
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