The ubiquitin ligase LIN41/TRIM71 targets p53 to antagonize cell death and differentiation pathways during stem cell differentiation

Abstract

Rapidity and specificity are characteristic features of proteolysis mediated by the ubiquitin-proteasome system. Therefore, the UPS is ideally suited for the remodeling of the embryonic stem cell proteome during the transition from pluripotent to differentiated states and its inverse, the generation of inducible pluripotent stem cells. The Trim-NHL family member LIN41 is among the first E3 ubiquitin ligases to be linked to stem cell pluripotency and reprogramming. Initially discovered in C. elegans as a downstream target of the let-7 miRNA, LIN41 is now recognized as a critical regulator of stem cell fates as well as the timing of neurogenesis. Despite being indispensable for embryonic development and neural tube closure in mice, the underlying mechanisms for LIN41 function in these processes are poorly understood. To better understand the specific contributions of the E3 ligase activity for the stem cell functions of LIN41, we characterized global changes in ubiquitin or ubiquitin-like modifications using Lin41-inducible mouse embryonic stem cells. The tumor suppressor protein p53 was among the five most strongly affected proteins in cells undergoing neural differentiation in response to LIN41 induction. We show that LIN41 interacts with p53, controls its abundance by ubiquitination and antagonizes p53-dependent pro-apoptotic and pro-differentiation responses. In vivo, the lack of LIN41 is associated with upregulation of Grhl3 and widespread caspase-3 activation, two downstream effectors of p53 with essential roles in neural tube closure. As Lin41-deficient mice display neural tube closure defects, we conclude that LIN41 is critical for the regulation of p53 functions in cell fate specification and survival during early brain development.

Regulation of the p53 Family Proteins by the Ubiquitin Proteasomal Pathway

“…Lastly, TRIM71 (also known as LIN41) has been demonstrated to regulate p53 during stem cell differentiation [117]. TRIM71 KO mice are embryonically lethal due to the failure of the neural tube to close during development [114,115].…”

“…TRIM71 KO mice are embryonically lethal due to the failure of the neural tube to close during development [114,115]. A recent study has demonstrated that TRIM71-mediated regulation of p53 is likely critical in facilitating normal embryonic stem cell differentiation and neurogenesis [117]. TRIM71 has been shown to bind p53 through its NHL domain, and is able to ubiquitinate p53 in embryonic stem cells [117].…”

“…A recent study has demonstrated that TRIM71-mediated regulation of p53 is likely critical in facilitating normal embryonic stem cell differentiation and neurogenesis [117]. TRIM71 has been shown to bind p53 through its NHL domain, and is able to ubiquitinate p53 in embryonic stem cells [117]. Loss of TRIM71 increases p53 protein levels and reduces ubiquitination of p53, while TRIM71 induction increases cell proliferation and reduces apoptosis in a p53-dependent manner [117].…”

“…TRIM71 has been shown to bind p53 through its NHL domain, and is able to ubiquitinate p53 in embryonic stem cells [117]. Loss of TRIM71 increases p53 protein levels and reduces ubiquitination of p53, while TRIM71 induction increases cell proliferation and reduces apoptosis in a p53-dependent manner [117]. Most importantly, TRIM71 KO embryos have shown significantly increased levels of p53 and caspase activation by E10.5 [117].…”

p53 induces ARTS to promote mitochondrial apoptosis

“…Intriguingly, through our recent work by screening mutant p53-interacting proteins in ovarian cancer as previously 9 described (Chen et al, 2019), we unexpectedly found that mutant p53 may interact with a peptide (KLQDQALKE) encoded by the SEPT4 gene through a co-immunoprecipitation (co-IP) assay coupled with mass spectrometry (MS) analysis ( Figure 4A). This observation prompted us to test if ARTS binds to wild-type p53 as well, because both wild-type and mutant p53 share common binding partners in many cases, such as MDM2 and TRIM71 (Nguyen et al, 2017, Chen et al, 2019. By co-expressing exogenous p53 and Flag-ARTS in H1299 cells followed by co-IP-IB assays, we found that exogenous p53 could be co-immunoprecipitated with Flag-ARTS using an anti-Flag antibody ( Figure 4B).…”