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Ninjurin1, a target of p53, regulates p53 expression and p53-dependent cell survival, senescence, and radiation-induced mortality

Cho, Seong-Jun, Rossi, Andrea, Jung, Yong-Sam, Yan, Wensheng, Liu, Gang, Zhang, Jin, Zhang, Min, Chen, Xinbin
Proceedings of the National Academy of Sciences of the United States of America 2013 v.110 no.23 pp. 9362-9367
DNA damage, adhesion, apoptosis, carcinogenesis, cell cycle checkpoints, cell proliferation, cell viability, heterozygosity, humans, ionization, messenger RNA, mice, mortality, neoplasms, nerve tissue, thymus gland, transcription (genetics), translation (genetics), tumor suppressor protein p53
The tumor suppressor protein p53 plays a crucial role in coordinating cellular processes, such as cell cycle arrest, apoptosis, and senescence. The nerve injury-induced protein 1 (Ninjurin1, Ninj1) is a homophilic adhesion molecule and involved in nerve regeneration. Interestingly, Ninj1 is found to be overexpressed in human cancer, but its role in tumorigenesis is not clear. Here, we found that Ninj1 is transcriptionally regulated by p53 and can be induced by DNA damage in a p53-dependent manner. We also found that knockout or knockdown of Ninj1 increases p53 expression potentially through enhanced p53 mRNA translation. In addition, we found that Ninj1 deficiency suppresses cell proliferation but enhances apoptosis and premature senescence in a p53-dependent manner. Consistent with this, we found that mice heterozygous in ninj1 are hypersensitive to ionizing radiation-induced lethality, along with increased expression of p53 in thymus. Taken together, we provided evidence that Ninj1 is a p53 target and modulates p53 mRNA translation and p53-dependent premature senescence, cell proliferation, apoptosis, and radiation-induced mortality in vitro and in vivo. Thus, we postulate that as a membrane adhesion molecule, Ninj1 is an ideal target to regulate p53 activity via the p53-Ninj1 loop.